[v21,0/9] Add REMOVE_BUF ioctl

Unlike when resolution change on keyframes, dynamic resolution change
on inter frames doesn't allow to do a stream off/on sequence because
it is need to keep all previous references alive to decode inter frames.
This constraint have two main problems:
- more memory consumption.
- more buffers in use.
To solve these issue this series introduce REMOVE_BUFS ioctl.

VP9 conformance tests using fluster give a score of 210/305.
The 24 of the 24 resize inter tests (vp90-2-21-resize_inter_* files) are ok
but require to use postprocessor.

Kernel branch is available here:
https://gitlab.collabora.com/benjamin.gaignard/for-upstream/-/commits/remove_vb2_queue_limit_v21

GStreamer branch to use DELETE_BUF ioctl and testing dynamic resolution
change is here:
https://gitlab.freedesktop.org/benjamin.gaignard1/gstreamer/-/commits/VP9_drc

changes in version 21:
- Be more careful about checking remove_bufs type field vs queue type.
- Add documentation about type checking error.
- Always set capabilities flags field.
- Do not set vidioc_remove_bufs for vim2m driver.

changes in version 20:
- Rename DELETE_BUFS into REMOVE_BUFS
- Change documention, structure and variables name to use 'remove'

changes in version 19:
- Fix typo in commit message.
- Fix ioctl domentation
- Rework q->is_busy patch following Hans's comments
- Change where DELETE_BUFS is enabled

Benjamin Gaignard (9):
  media: videobuf2: Update vb2_is_busy() logic
  videobuf2: Add min_reqbufs_allocation field to vb2_queue structure
  media: test-drivers: Set REQBUFS minimum number of buffers
  media: core: Rework how create_buf index returned value is computed
  media: core: Add bitmap manage bufs array entries
  media: core: Free range of buffers
  media: v4l2: Add REMOVE_BUFS ioctl
  media: v4l2: Add mem2mem helpers for REMOVE_BUFS ioctl
  media: verisilicon: Support removing buffers on capture queue

 .../userspace-api/media/v4l/user-func.rst     |   1 +
 .../media/v4l/vidioc-remove-bufs.rst          |  85 +++++++
 .../media/v4l/vidioc-reqbufs.rst              |   1 +
 .../media/common/videobuf2/videobuf2-core.c   | 223 ++++++++++++------
 .../media/common/videobuf2/videobuf2-v4l2.c   |  34 ++-
 .../media/platform/verisilicon/hantro_v4l2.c  |   1 +
 .../media/test-drivers/vicodec/vicodec-core.c |   1 +
 .../media/test-drivers/vimc/vimc-capture.c    |   3 +-
 drivers/media/test-drivers/visl/visl-video.c  |   1 +
 drivers/media/test-drivers/vivid/vivid-core.c |   5 +-
 drivers/media/v4l2-core/v4l2-dev.c            |   3 +
 drivers/media/v4l2-core/v4l2-ioctl.c          |  30 +++
 drivers/media/v4l2-core/v4l2-mem2mem.c        |  15 ++
 include/media/v4l2-ioctl.h                    |   4 +
 include/media/v4l2-mem2mem.h                  |   2 +
 include/media/videobuf2-core.h                |  52 +++-
 include/media/videobuf2-v4l2.h                |   2 +
 include/uapi/linux/videodev2.h                |  17 ++
 18 files changed, 394 insertions(+), 86 deletions(-)
 create mode 100644 Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst

Em Thu, 14 Mar 2024 16:32:18 +0100
Benjamin Gaignard <benjamin.gaignard@collabora.com> escreveu:

> Do not rely on the number of allocated buffers to know if the
> queue is busy but on a flag set when at least one buffer has been allocated
> by REQBUFS or CREATE_BUFS ioctl.
> The flag is reset when REQBUFS is called with count = 0 or the file
> handle is closed.
> This is needed because remove buffers feature will be able to remove
> all the buffers from a queue while streaming so relying on the number
> of allocated buffers in the queue won't be possible.
> 
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Reviewed-by: Mauro Carvalho Chehab <mchehab@kernel.org>

> ---
>  drivers/media/common/videobuf2/videobuf2-core.c | 4 ++++
>  include/media/videobuf2-core.h                  | 4 +++-
>  2 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index b6bf8f232f48..d8b3c04cb3b5 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -854,6 +854,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
>  		__vb2_queue_free(q, q_num_bufs);
>  		mutex_unlock(&q->mmap_lock);
>  
> +		q->is_busy = 0;
>  		/*
>  		 * In case of REQBUFS(0) return immediately without calling
>  		 * driver's queue_setup() callback and allocating resources.
> @@ -966,6 +967,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
>  	 */
>  	*count = allocated_buffers;
>  	q->waiting_for_buffers = !q->is_output;
> +	q->is_busy = 1;
>  
>  	return 0;
>  
> @@ -1091,6 +1093,7 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
>  	 * to the userspace.
>  	 */
>  	*count = allocated_buffers;
> +	q->is_busy = 1;
>  
>  	return 0;
>  
> @@ -2555,6 +2558,7 @@ void vb2_core_queue_release(struct vb2_queue *q)
>  	__vb2_queue_free(q, vb2_get_num_buffers(q));
>  	kfree(q->bufs);
>  	q->bufs = NULL;
> +	q->is_busy = 0;
>  	mutex_unlock(&q->mmap_lock);
>  }
>  EXPORT_SYMBOL_GPL(vb2_core_queue_release);
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index 8b86996b2719..667bf9ee1101 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -582,6 +582,7 @@ struct vb2_buf_ops {
>   *		released. Used to prevent destroying the queue by other threads.
>   * @is_multiplanar: set if buffer type is multiplanar
>   * @is_output:	set if buffer type is output
> + * @is_busy:	set if at least one buffer has been allocated at some time.
>   * @copy_timestamp: set if vb2-core should set timestamps
>   * @last_buffer_dequeued: used in poll() and DQBUF to immediately return if the
>   *		last decoded buffer was already dequeued. Set for capture queues
> @@ -647,6 +648,7 @@ struct vb2_queue {
>  	unsigned int			waiting_in_dqbuf:1;
>  	unsigned int			is_multiplanar:1;
>  	unsigned int			is_output:1;
> +	unsigned int			is_busy:1;
>  	unsigned int			copy_timestamp:1;
>  	unsigned int			last_buffer_dequeued:1;
>  
> @@ -1166,7 +1168,7 @@ static inline unsigned int vb2_get_num_buffers(struct vb2_queue *q)
>   */
>  static inline bool vb2_is_busy(struct vb2_queue *q)
>  {
> -	return vb2_get_num_buffers(q) > 0;
> +	return !!q->is_busy;
>  }
>  
>  /**



Thanks,
Mauro

Em Thu, 14 Mar 2024 16:32:20 +0100
Benjamin Gaignard <benjamin.gaignard@collabora.com> escreveu:

> Instead of using 'min_queued_buffers' field to specify the
> minimum number of buffers to be allocated when calling REQBUF
> use 'min_reqbufs_allocation' field which is dedicated to this
> purpose.
> 
> While at it rename vivid_create_queue() parameter.

LGTM.
Reviewed-by: Mauro Carvalho Chehab <mchehab@kernel.org>
> 
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
> ---
>  drivers/media/test-drivers/vimc/vimc-capture.c | 2 +-
>  drivers/media/test-drivers/vivid/vivid-core.c  | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/test-drivers/vimc/vimc-capture.c b/drivers/media/test-drivers/vimc/vimc-capture.c
> index 2a2d19d23bab..97693561f1e4 100644
> --- a/drivers/media/test-drivers/vimc/vimc-capture.c
> +++ b/drivers/media/test-drivers/vimc/vimc-capture.c
> @@ -432,7 +432,7 @@ static struct vimc_ent_device *vimc_capture_add(struct vimc_device *vimc,
>  	q->mem_ops = vimc_allocator == VIMC_ALLOCATOR_DMA_CONTIG
>  		   ? &vb2_dma_contig_memops : &vb2_vmalloc_memops;
>  	q->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
> -	q->min_queued_buffers = 2;
> +	q->min_reqbufs_allocation = 2;
>  	q->lock = &vcapture->lock;
>  	q->dev = v4l2_dev->dev;
>  
> diff --git a/drivers/media/test-drivers/vivid/vivid-core.c b/drivers/media/test-drivers/vivid/vivid-core.c
> index 159c72cbb5bf..11b8520d9f57 100644
> --- a/drivers/media/test-drivers/vivid/vivid-core.c
> +++ b/drivers/media/test-drivers/vivid/vivid-core.c
> @@ -861,7 +861,7 @@ static const struct media_device_ops vivid_media_ops = {
>  static int vivid_create_queue(struct vivid_dev *dev,
>  			      struct vb2_queue *q,
>  			      u32 buf_type,
> -			      unsigned int min_queued_buffers,
> +			      unsigned int min_reqbufs_allocation,
>  			      const struct vb2_ops *ops)
>  {
>  	if (buf_type == V4L2_BUF_TYPE_VIDEO_CAPTURE && dev->multiplanar)
> @@ -898,7 +898,7 @@ static int vivid_create_queue(struct vivid_dev *dev,
>  	q->mem_ops = allocators[dev->inst] == 1 ? &vb2_dma_contig_memops :
>  						  &vb2_vmalloc_memops;
>  	q->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
> -	q->min_queued_buffers = supports_requests[dev->inst] ? 0 : min_queued_buffers;
> +	q->min_reqbufs_allocation = min_reqbufs_allocation;
>  	q->lock = &dev->mutex;
>  	q->dev = dev->v4l2_dev.dev;
>  	q->supports_requests = supports_requests[dev->inst];



Thanks,
Mauro

Em Thu, 14 Mar 2024 16:32:24 +0100
Benjamin Gaignard <benjamin.gaignard@collabora.com> escreveu:

> VIDIOC_REMOVE_BUFS ioctl allows to remove buffers from a queue.
> The number of buffers to remove in given by count field of
> struct v4l2_remove_buffers and the range start at the index
> specified in the same structure.
> 
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
> ---
> changes in version 21:
> - Be more careful about checking remove_bufs type field vs queue type.
> - Add documentation about type checking error.
> - Always set capabilities flags field.
> 
>  .../userspace-api/media/v4l/user-func.rst     |  1 +
>  .../media/v4l/vidioc-remove-bufs.rst          | 85 +++++++++++++++++++
>  .../media/v4l/vidioc-reqbufs.rst              |  1 +
>  .../media/common/videobuf2/videobuf2-core.c   | 38 +++++++++
>  .../media/common/videobuf2/videobuf2-v4l2.c   | 20 ++++-
>  drivers/media/v4l2-core/v4l2-dev.c            |  3 +
>  drivers/media/v4l2-core/v4l2-ioctl.c          | 30 +++++++
>  include/media/v4l2-ioctl.h                    |  4 +
>  include/media/videobuf2-core.h                | 10 +++
>  include/media/videobuf2-v4l2.h                |  2 +
>  include/uapi/linux/videodev2.h                | 17 ++++
>  11 files changed, 210 insertions(+), 1 deletion(-)
>  create mode 100644 Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst
> 
> diff --git a/Documentation/userspace-api/media/v4l/user-func.rst b/Documentation/userspace-api/media/v4l/user-func.rst
> index 15ff0bf7bbe6..6f661138801c 100644
> --- a/Documentation/userspace-api/media/v4l/user-func.rst
> +++ b/Documentation/userspace-api/media/v4l/user-func.rst
> @@ -62,6 +62,7 @@ Function Reference
>      vidioc-query-dv-timings
>      vidioc-querystd
>      vidioc-reqbufs
> +    vidioc-remove-bufs
>      vidioc-s-hw-freq-seek
>      vidioc-streamon
>      vidioc-subdev-enum-frame-interval
> diff --git a/Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst b/Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst
> new file mode 100644
> index 000000000000..0cbc8c7313b7
> --- /dev/null
> +++ b/Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst
> @@ -0,0 +1,85 @@
> +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
> +.. c:namespace:: V4L
> +
> +.. _VIDIOC_REMOVE_BUFS:
> +
> +************************
> +ioctl VIDIOC_REMOVE_BUFS
> +************************
> +
> +Name
> +====
> +
> +VIDIOC_REMOVE_BUFS - Removes buffers from a queue
> +
> +Synopsis
> +========
> +
> +.. c:macro:: VIDIOC_REMOVE_BUFS
> +
> +``int ioctl(int fd, VIDIOC_REMOVE_BUFS, struct v4l2_remove_buffers *argp)``
> +
> +Arguments
> +=========
> +
> +``fd``
> +    File descriptor returned by :c:func:`open()`.
> +
> +``argp``
> +    Pointer to struct :c:type:`v4l2_remove_buffers`.
> +
> +Description
> +===========
> +
> +Applications can optionally call the :ref:`VIDIOC_REMOVE_BUFS` ioctl to
> +remove buffers from a queue.
> +:ref:`VIDIOC_CREATE_BUFS` ioctl support is mandatory to enable :ref:`VIDIOC_REMOVE_BUFS`.
> +This ioctl is available if the ``V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS`` capability
> +is set on the queue when :c:func:`VIDIOC_REQBUFS` or :c:func:`VIDIOC_CREATE_BUFS`
> +are invoked.
> +
> +.. c:type:: v4l2_remove_buffers
> +
> +.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
> +
> +.. flat-table:: struct v4l2_remove_buffers
> +    :header-rows:  0
> +    :stub-columns: 0
> +    :widths:       1 1 2
> +
> +    * - __u32
> +      - ``index``
> +      - The starting buffer index to remove. This field is ignored if count == 0.
> +    * - __u32
> +      - ``count``
> +      - The number of buffers to be removed with indices 'index' until 'index + count - 1'.
> +        All buffers in this range must be valid and in DEQUEUED state.
> +        :ref:`VIDIOC_REMOVE_BUFS` will always check the validity of ``type`, if it is
> +        invalid it returns ``EINVAL`` error code.
> +        If count is set to 0 :ref:`VIDIOC_REMOVE_BUFS` will do nothing and return 0.
> +    * - __u32
> +      - ``type``
> +      - Type of the stream or buffers, this is the same as the struct
> +	:c:type:`v4l2_format` ``type`` field. See
> +	:c:type:`v4l2_buf_type` for valid values.
> +    * - __u32
> +      - ``reserved``\ [13]
> +      - A place holder for future extensions. Drivers and applications
> +	must set the array to zero.
> +
> +Return Value
> +============
> +
> +On success 0 is returned, on error -1 and the ``errno`` variable is set
> +appropriately. The generic error codes are described at the
> +:ref:`Generic Error Codes <gen-errors>` chapter.

It is not enough to just return an error code. it should also describe
what will be the expected behavior after the call. Something like:

	If an error occurs, no buffers will be freed and one of the
	error codes below will be returned:

> +
> +EBUSY
> +    File I/O is in progress.
> +    One or more of the buffers in the range ``index`` to ``index + count - 1`` are not
> +    in DEQUEUED state.
> +
> +EINVAL
> +    One or more of the buffers in the range ``index`` to ``index + count - 1`` do not
> +    exist in the queue.
> +    The buffer type (``type`` field) is not valid.

IMO, it needs also another error code: as there's a minimal number of
buffers to be queued (let's say, 2), what happens if there are currently
3 buffers allocated and an ioctl is called to free 2 buffers?

IMO, it shall return an error code and not free any buffers.

The best would be to return a code different than EINVAL. Maybe E2BIG?

> diff --git a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
> index 0b3a41a45d05..bbc22dd76032 100644
> --- a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
> +++ b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
> @@ -121,6 +121,7 @@ aborting or finishing any DMA in progress, an implicit
>  .. _V4L2-BUF-CAP-SUPPORTS-M2M-HOLD-CAPTURE-BUF:
>  .. _V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS:
>  .. _V4L2-BUF-CAP-SUPPORTS-MAX-NUM-BUFFERS:
> +.. _V4L2-BUF-CAP-SUPPORTS-REMOVE-BUFS:
>  
>  .. raw:: latex
>  
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index 009cea95d662..0b2b48e1b2df 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -1691,6 +1691,44 @@ int vb2_core_prepare_buf(struct vb2_queue *q, struct vb2_buffer *vb, void *pb)
>  }
>  EXPORT_SYMBOL_GPL(vb2_core_prepare_buf);
>  
> +int vb2_core_remove_bufs(struct vb2_queue *q, unsigned int start, unsigned int count)
> +{
> +	unsigned int i, ret = 0;
> +	unsigned int q_num_bufs = vb2_get_num_buffers(q);
> +
> +	if (count == 0)
> +		return 0;
> +
> +	if (count > q_num_bufs)
> +		return -EINVAL;

It also needs:

	if (q_num_bufs - count < q->min_reqbufs_allocation && q_num_bufs != count)
		return <some error code>;

e. g. it shall not accept keeping, for instance, just one buffer allocated.

> +
> +	if (start > q->max_num_buffers - count)
> +		return -EINVAL;
> +
> +	mutex_lock(&q->mmap_lock);
> +
> +	/* Check that all buffers in the range exist */
> +	for (i = start; i < start + count; i++) {
> +		struct vb2_buffer *vb = vb2_get_buffer(q, i);
> +
> +		if (!vb) {
> +			ret = -EINVAL;
> +			goto unlock;
> +		}
> +		if (vb->state != VB2_BUF_STATE_DEQUEUED) {
> +			ret = -EBUSY;
> +			goto unlock;
> +		}
> +	}
> +	__vb2_queue_free(q, start, count);
> +	dprintk(q, 2, "%u buffers removed\n", count);
> +
> +unlock:
> +	mutex_unlock(&q->mmap_lock);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(vb2_core_remove_bufs);
> +
>  /*
>   * vb2_start_streaming() - Attempt to start streaming.
>   * @q:		videobuf2 queue
> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> index 03e8080a68a8..293f3d5f1c4e 100644
> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> @@ -685,7 +685,7 @@ static void vb2_set_flags_and_caps(struct vb2_queue *q, u32 memory,
>  		*flags &= V4L2_MEMORY_FLAG_NON_COHERENT;
>  	}
>  
> -	*caps = V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
> +	*caps |= V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
>  	if (q->io_modes & VB2_MMAP)
>  		*caps |= V4L2_BUF_CAP_SUPPORTS_MMAP;
>  	if (q->io_modes & VB2_USERPTR)
> @@ -1001,6 +1001,24 @@ EXPORT_SYMBOL_GPL(vb2_poll);
>  
>  /* vb2 ioctl helpers */
>  
> +int vb2_ioctl_remove_bufs(struct file *file, void *priv,
> +			  struct v4l2_remove_buffers *d)
> +{
> +	struct video_device *vdev = video_devdata(file);
> +
> +	if (vdev->queue->type != d->type)
> +		return -EINVAL;
> +
> +	if (d->count == 0)
> +		return 0;
> +
> +	if (vb2_queue_is_busy(vdev->queue, file))
> +		return -EBUSY;
> +
> +	return vb2_core_remove_bufs(vdev->queue, d->index, d->count);
> +}
> +EXPORT_SYMBOL_GPL(vb2_ioctl_remove_bufs);
> +
>  int vb2_ioctl_reqbufs(struct file *file, void *priv,
>  			  struct v4l2_requestbuffers *p)
>  {
> diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
> index d13954bd31fd..e39e9742fdb5 100644
> --- a/drivers/media/v4l2-core/v4l2-dev.c
> +++ b/drivers/media/v4l2-core/v4l2-dev.c
> @@ -722,6 +722,9 @@ static void determine_valid_ioctls(struct video_device *vdev)
>  		SET_VALID_IOCTL(ops, VIDIOC_PREPARE_BUF, vidioc_prepare_buf);
>  		SET_VALID_IOCTL(ops, VIDIOC_STREAMON, vidioc_streamon);
>  		SET_VALID_IOCTL(ops, VIDIOC_STREAMOFF, vidioc_streamoff);
> +		/* VIDIOC_CREATE_BUFS support is mandatory to enable VIDIOC_REMOVE_BUFS */
> +		if (ops->vidioc_create_bufs)
> +			SET_VALID_IOCTL(ops, VIDIOC_REMOVE_BUFS, vidioc_remove_bufs);
>  	}
>  
>  	if (is_vid || is_vbi || is_meta) {
> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> index 6e7b8b682d13..5aeff5519407 100644
> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> @@ -489,6 +489,14 @@ static void v4l_print_create_buffers(const void *arg, bool write_only)
>  	v4l_print_format(&p->format, write_only);
>  }
>  
> +static void v4l_print_remove_buffers(const void *arg, bool write_only)
> +{
> +	const struct v4l2_remove_buffers *p = arg;
> +
> +	pr_cont("type=%s, index=%u, count=%u\n",
> +		prt_names(p->type, v4l2_type_names), p->index, p->count);
> +}
> +
>  static void v4l_print_streamparm(const void *arg, bool write_only)
>  {
>  	const struct v4l2_streamparm *p = arg;
> @@ -2092,6 +2100,7 @@ static int v4l_overlay(const struct v4l2_ioctl_ops *ops,
>  static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,
>  				struct file *file, void *fh, void *arg)
>  {
> +	struct video_device *vfd = video_devdata(file);
>  	struct v4l2_requestbuffers *p = arg;
>  	int ret = check_fmt(file, p->type);
>  
> @@ -2100,6 +2109,10 @@ static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,
>  
>  	memset_after(p, 0, flags);
>  
> +	p->capabilities = 0;
> +	if (is_valid_ioctl(vfd, VIDIOC_REMOVE_BUFS))
> +		p->capabilities = V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS;
> +
>  	return ops->vidioc_reqbufs(file, fh, p);
>  }
>  
> @@ -2133,6 +2146,7 @@ static int v4l_dqbuf(const struct v4l2_ioctl_ops *ops,
>  static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
>  				struct file *file, void *fh, void *arg)
>  {
> +	struct video_device *vfd = video_devdata(file);
>  	struct v4l2_create_buffers *create = arg;
>  	int ret = check_fmt(file, create->format.type);
>  
> @@ -2143,6 +2157,10 @@ static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
>  
>  	v4l_sanitize_format(&create->format);
>  
> +	create->capabilities = 0;
> +	if (is_valid_ioctl(vfd, VIDIOC_REMOVE_BUFS))
> +		create->capabilities = V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS;
> +
>  	ret = ops->vidioc_create_bufs(file, fh, create);
>  
>  	if (create->format.type == V4L2_BUF_TYPE_VIDEO_CAPTURE ||
> @@ -2161,6 +2179,17 @@ static int v4l_prepare_buf(const struct v4l2_ioctl_ops *ops,
>  	return ret ? ret : ops->vidioc_prepare_buf(file, fh, b);
>  }
>  
> +static int v4l_remove_bufs(const struct v4l2_ioctl_ops *ops,
> +			   struct file *file, void *fh, void *arg)
> +{
> +	struct v4l2_remove_buffers *remove = arg;
> +
> +	if (ops->vidioc_remove_bufs)
> +		return ops->vidioc_remove_bufs(file, fh, remove);
> +
> +	return -ENOTTY;
> +}
> +
>  static int v4l_g_parm(const struct v4l2_ioctl_ops *ops,
>  				struct file *file, void *fh, void *arg)
>  {
> @@ -2910,6 +2939,7 @@ static const struct v4l2_ioctl_info v4l2_ioctls[] = {
>  	IOCTL_INFO(VIDIOC_ENUM_FREQ_BANDS, v4l_enum_freq_bands, v4l_print_freq_band, 0),
>  	IOCTL_INFO(VIDIOC_DBG_G_CHIP_INFO, v4l_dbg_g_chip_info, v4l_print_dbg_chip_info, INFO_FL_CLEAR(v4l2_dbg_chip_info, match)),
>  	IOCTL_INFO(VIDIOC_QUERY_EXT_CTRL, v4l_query_ext_ctrl, v4l_print_query_ext_ctrl, INFO_FL_CTRL | INFO_FL_CLEAR(v4l2_query_ext_ctrl, id)),
> +	IOCTL_INFO(VIDIOC_REMOVE_BUFS, v4l_remove_bufs, v4l_print_remove_buffers, INFO_FL_PRIO | INFO_FL_QUEUE | INFO_FL_CLEAR(v4l2_remove_buffers, type)),
>  };
>  #define V4L2_IOCTLS ARRAY_SIZE(v4l2_ioctls)
>  
> diff --git a/include/media/v4l2-ioctl.h b/include/media/v4l2-ioctl.h
> index edb733f21604..bdbb7e542321 100644
> --- a/include/media/v4l2-ioctl.h
> +++ b/include/media/v4l2-ioctl.h
> @@ -163,6 +163,8 @@ struct v4l2_fh;
>   *	:ref:`VIDIOC_CREATE_BUFS <vidioc_create_bufs>` ioctl
>   * @vidioc_prepare_buf: pointer to the function that implements
>   *	:ref:`VIDIOC_PREPARE_BUF <vidioc_prepare_buf>` ioctl
> + * @vidioc_remove_bufs: pointer to the function that implements
> + *	:ref:`VIDIOC_REMOVE_BUFS <vidioc_remove_bufs>` ioctl
>   * @vidioc_overlay: pointer to the function that implements
>   *	:ref:`VIDIOC_OVERLAY <vidioc_overlay>` ioctl
>   * @vidioc_g_fbuf: pointer to the function that implements
> @@ -422,6 +424,8 @@ struct v4l2_ioctl_ops {
>  				  struct v4l2_create_buffers *b);
>  	int (*vidioc_prepare_buf)(struct file *file, void *fh,
>  				  struct v4l2_buffer *b);
> +	int (*vidioc_remove_bufs)(struct file *file, void *fh,
> +				  struct v4l2_remove_buffers *d);
>  
>  	int (*vidioc_overlay)(struct file *file, void *fh, unsigned int i);
>  	int (*vidioc_g_fbuf)(struct file *file, void *fh,
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index b9333e2c7797..955237ac503d 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -870,6 +870,16 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
>   */
>  int vb2_core_prepare_buf(struct vb2_queue *q, struct vb2_buffer *vb, void *pb);
>  
> +/**
> + * vb2_core_remove_bufs() -
> + * @q:		pointer to &struct vb2_queue with videobuf2 queue.
> + * @start:	first index of the range of buffers to remove.
> + * @count:	number of buffers to remove.
> + *
> + *  Return: returns zero on success; an error code otherwise.
> + */
> +int vb2_core_remove_bufs(struct vb2_queue *q, unsigned int start, unsigned int count);
> +
>  /**
>   * vb2_core_qbuf() - Queue a buffer from userspace
>   *
> diff --git a/include/media/videobuf2-v4l2.h b/include/media/videobuf2-v4l2.h
> index 5a845887850b..77ce8238ab30 100644
> --- a/include/media/videobuf2-v4l2.h
> +++ b/include/media/videobuf2-v4l2.h
> @@ -334,6 +334,8 @@ int vb2_ioctl_streamon(struct file *file, void *priv, enum v4l2_buf_type i);
>  int vb2_ioctl_streamoff(struct file *file, void *priv, enum v4l2_buf_type i);
>  int vb2_ioctl_expbuf(struct file *file, void *priv,
>  	struct v4l2_exportbuffer *p);
> +int vb2_ioctl_remove_bufs(struct file *file, void *priv,
> +			  struct v4l2_remove_buffers *p);
>  
>  /* struct v4l2_file_operations helpers */
>  
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index a8015e5e7fa4..2663213b76a4 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -1036,6 +1036,7 @@ struct v4l2_requestbuffers {
>  #define V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF	(1 << 5)
>  #define V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS		(1 << 6)
>  #define V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS		(1 << 7)
> +#define V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS		(1 << 8)
>  
>  /**
>   * struct v4l2_plane - plane info for multi-planar buffers
> @@ -2624,6 +2625,20 @@ struct v4l2_create_buffers {
>  	__u32			reserved[5];
>  };
>  
> +/**
> + * struct v4l2_remove_buffers - VIDIOC_REMOVE_BUFS argument
> + * @index:	the first buffer to be removed
> + * @count:	number of buffers to removed
> + * @type:	enum v4l2_buf_type
> + * @reserved:	future extensions
> + */
> +struct v4l2_remove_buffers {
> +	__u32			index;
> +	__u32			count;
> +	__u32			type;
> +	__u32			reserved[13];
> +};
> +
>  /*
>   *	I O C T L   C O D E S   F O R   V I D E O   D E V I C E S
>   *
> @@ -2723,6 +2738,8 @@ struct v4l2_create_buffers {
>  #define VIDIOC_DBG_G_CHIP_INFO  _IOWR('V', 102, struct v4l2_dbg_chip_info)
>  
>  #define VIDIOC_QUERY_EXT_CTRL	_IOWR('V', 103, struct v4l2_query_ext_ctrl)
> +#define VIDIOC_REMOVE_BUFS	_IOWR('V', 104, struct v4l2_remove_buffers)
> +
>  
>  /* Reminder: when adding new ioctls please add support for them to
>     drivers/media/v4l2-core/v4l2-compat-ioctl32.c as well! */



Thanks,
Mauro

Em Thu, 14 Mar 2024 16:32:26 +0100
Benjamin Gaignard <benjamin.gaignard@collabora.com> escreveu:

> Allow to remove buffers on capture queue because it the one which
> own the decoded buffers. After a dynamic resolution change lot of
> them could remain allocated but won't be used anymore so deleting
> them save memory.


LGTM.

Reviewed-by: Mauro Carvalho Chehab <mchehab@kernel.org>
> 
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
> ---
>  drivers/media/platform/verisilicon/hantro_v4l2.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/media/platform/verisilicon/hantro_v4l2.c b/drivers/media/platform/verisilicon/hantro_v4l2.c
> index 941fa23c211a..df6f2536263b 100644
> --- a/drivers/media/platform/verisilicon/hantro_v4l2.c
> +++ b/drivers/media/platform/verisilicon/hantro_v4l2.c
> @@ -756,6 +756,7 @@ const struct v4l2_ioctl_ops hantro_ioctl_ops = {
>  	.vidioc_dqbuf = v4l2_m2m_ioctl_dqbuf,
>  	.vidioc_prepare_buf = v4l2_m2m_ioctl_prepare_buf,
>  	.vidioc_create_bufs = v4l2_m2m_ioctl_create_bufs,
> +	.vidioc_remove_bufs = v4l2_m2m_ioctl_remove_bufs,
>  	.vidioc_expbuf = v4l2_m2m_ioctl_expbuf,
>  
>  	.vidioc_subscribe_event = v4l2_ctrl_subscribe_event,



Thanks,
Mauro

On 21/03/2024 3:14 pm, Mauro Carvalho Chehab wrote:
> Em Thu, 14 Mar 2024 16:32:24 +0100
> Benjamin Gaignard <benjamin.gaignard@collabora.com> escreveu:
> 
>> VIDIOC_REMOVE_BUFS ioctl allows to remove buffers from a queue.
>> The number of buffers to remove in given by count field of
>> struct v4l2_remove_buffers and the range start at the index
>> specified in the same structure.
>>
>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
>> ---
>> changes in version 21:
>> - Be more careful about checking remove_bufs type field vs queue type.
>> - Add documentation about type checking error.
>> - Always set capabilities flags field.
>>
>>  .../userspace-api/media/v4l/user-func.rst     |  1 +
>>  .../media/v4l/vidioc-remove-bufs.rst          | 85 +++++++++++++++++++
>>  .../media/v4l/vidioc-reqbufs.rst              |  1 +
>>  .../media/common/videobuf2/videobuf2-core.c   | 38 +++++++++
>>  .../media/common/videobuf2/videobuf2-v4l2.c   | 20 ++++-
>>  drivers/media/v4l2-core/v4l2-dev.c            |  3 +
>>  drivers/media/v4l2-core/v4l2-ioctl.c          | 30 +++++++
>>  include/media/v4l2-ioctl.h                    |  4 +
>>  include/media/videobuf2-core.h                | 10 +++
>>  include/media/videobuf2-v4l2.h                |  2 +
>>  include/uapi/linux/videodev2.h                | 17 ++++
>>  11 files changed, 210 insertions(+), 1 deletion(-)
>>  create mode 100644 Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst
>>
>> diff --git a/Documentation/userspace-api/media/v4l/user-func.rst b/Documentation/userspace-api/media/v4l/user-func.rst
>> index 15ff0bf7bbe6..6f661138801c 100644
>> --- a/Documentation/userspace-api/media/v4l/user-func.rst
>> +++ b/Documentation/userspace-api/media/v4l/user-func.rst
>> @@ -62,6 +62,7 @@ Function Reference
>>      vidioc-query-dv-timings
>>      vidioc-querystd
>>      vidioc-reqbufs
>> +    vidioc-remove-bufs
>>      vidioc-s-hw-freq-seek
>>      vidioc-streamon
>>      vidioc-subdev-enum-frame-interval
>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst b/Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst
>> new file mode 100644
>> index 000000000000..0cbc8c7313b7
>> --- /dev/null
>> +++ b/Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst
>> @@ -0,0 +1,85 @@
>> +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
>> +.. c:namespace:: V4L
>> +
>> +.. _VIDIOC_REMOVE_BUFS:
>> +
>> +************************
>> +ioctl VIDIOC_REMOVE_BUFS
>> +************************
>> +
>> +Name
>> +====
>> +
>> +VIDIOC_REMOVE_BUFS - Removes buffers from a queue
>> +
>> +Synopsis
>> +========
>> +
>> +.. c:macro:: VIDIOC_REMOVE_BUFS
>> +
>> +``int ioctl(int fd, VIDIOC_REMOVE_BUFS, struct v4l2_remove_buffers *argp)``
>> +
>> +Arguments
>> +=========
>> +
>> +``fd``
>> +    File descriptor returned by :c:func:`open()`.
>> +
>> +``argp``
>> +    Pointer to struct :c:type:`v4l2_remove_buffers`.
>> +
>> +Description
>> +===========
>> +
>> +Applications can optionally call the :ref:`VIDIOC_REMOVE_BUFS` ioctl to
>> +remove buffers from a queue.
>> +:ref:`VIDIOC_CREATE_BUFS` ioctl support is mandatory to enable :ref:`VIDIOC_REMOVE_BUFS`.
>> +This ioctl is available if the ``V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS`` capability
>> +is set on the queue when :c:func:`VIDIOC_REQBUFS` or :c:func:`VIDIOC_CREATE_BUFS`
>> +are invoked.
>> +
>> +.. c:type:: v4l2_remove_buffers
>> +
>> +.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
>> +
>> +.. flat-table:: struct v4l2_remove_buffers
>> +    :header-rows:  0
>> +    :stub-columns: 0
>> +    :widths:       1 1 2
>> +
>> +    * - __u32
>> +      - ``index``
>> +      - The starting buffer index to remove. This field is ignored if count == 0.
>> +    * - __u32
>> +      - ``count``
>> +      - The number of buffers to be removed with indices 'index' until 'index + count - 1'.
>> +        All buffers in this range must be valid and in DEQUEUED state.
>> +        :ref:`VIDIOC_REMOVE_BUFS` will always check the validity of ``type`, if it is
>> +        invalid it returns ``EINVAL`` error code.
>> +        If count is set to 0 :ref:`VIDIOC_REMOVE_BUFS` will do nothing and return 0.
>> +    * - __u32
>> +      - ``type``
>> +      - Type of the stream or buffers, this is the same as the struct
>> +	:c:type:`v4l2_format` ``type`` field. See
>> +	:c:type:`v4l2_buf_type` for valid values.
>> +    * - __u32
>> +      - ``reserved``\ [13]
>> +      - A place holder for future extensions. Drivers and applications
>> +	must set the array to zero.
>> +
>> +Return Value
>> +============
>> +
>> +On success 0 is returned, on error -1 and the ``errno`` variable is set
>> +appropriately. The generic error codes are described at the
>> +:ref:`Generic Error Codes <gen-errors>` chapter.
> 
> It is not enough to just return an error code. it should also describe
> what will be the expected behavior after the call. Something like:
> 
> 	If an error occurs, no buffers will be freed and one of the
> 	error codes below will be returned:

That's good to have. That is indeed not stated explicitly.

> 
>> +
>> +EBUSY
>> +    File I/O is in progress.
>> +    One or more of the buffers in the range ``index`` to ``index + count - 1`` are not
>> +    in DEQUEUED state.
>> +
>> +EINVAL
>> +    One or more of the buffers in the range ``index`` to ``index + count - 1`` do not
>> +    exist in the queue.
>> +    The buffer type (``type`` field) is not valid.
> 
> IMO, it needs also another error code: as there's a minimal number of
> buffers to be queued (let's say, 2), what happens if there are currently
> 3 buffers allocated and an ioctl is called to free 2 buffers?
> 
> IMO, it shall return an error code and not free any buffers.

Note the requirement that all buffers you want to remove have to be in dequeued
state. So you can never remove buffers that are still in flight. An attempt to
do that results in EBUSY.

So there is no need for an other error code.

> 
> The best would be to return a code different than EINVAL. Maybe E2BIG?
> 
>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
>> index 0b3a41a45d05..bbc22dd76032 100644
>> --- a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
>> +++ b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
>> @@ -121,6 +121,7 @@ aborting or finishing any DMA in progress, an implicit
>>  .. _V4L2-BUF-CAP-SUPPORTS-M2M-HOLD-CAPTURE-BUF:
>>  .. _V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS:
>>  .. _V4L2-BUF-CAP-SUPPORTS-MAX-NUM-BUFFERS:
>> +.. _V4L2-BUF-CAP-SUPPORTS-REMOVE-BUFS:
>>  
>>  .. raw:: latex
>>  
>> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
>> index 009cea95d662..0b2b48e1b2df 100644
>> --- a/drivers/media/common/videobuf2/videobuf2-core.c
>> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
>> @@ -1691,6 +1691,44 @@ int vb2_core_prepare_buf(struct vb2_queue *q, struct vb2_buffer *vb, void *pb)
>>  }
>>  EXPORT_SYMBOL_GPL(vb2_core_prepare_buf);
>>  
>> +int vb2_core_remove_bufs(struct vb2_queue *q, unsigned int start, unsigned int count)
>> +{
>> +	unsigned int i, ret = 0;
>> +	unsigned int q_num_bufs = vb2_get_num_buffers(q);
>> +
>> +	if (count == 0)
>> +		return 0;
>> +
>> +	if (count > q_num_bufs)
>> +		return -EINVAL;
> 
> It also needs:
> 
> 	if (q_num_bufs - count < q->min_reqbufs_allocation && q_num_bufs != count)
> 		return <some error code>;
> 
> e. g. it shall not accept keeping, for instance, just one buffer allocated.

That's perfectly fine. The min_reqbufs_allocation is specific to VIDIOC_REQBUFS
(hence the name). If you use CREATE_BUFS/REMOVE_BUFS, then you are fully responsible
for allocating and removing buffers.

This is something that was discussed in earlier revisions of this series.

It is actually rather ugly that REQBUFS does this, but we need to keep that behavior
since that's how REQBUFS worked historically.

VIDIOC_CREATE_BUFS was never affected by this, so if you want to allocate N
buffers with CREATE_BUFS, then you'll never get more than N buffers (you might get
less, of course).

Regards,

	Hans

> 
>> +
>> +	if (start > q->max_num_buffers - count)
>> +		return -EINVAL;
>> +
>> +	mutex_lock(&q->mmap_lock);
>> +
>> +	/* Check that all buffers in the range exist */
>> +	for (i = start; i < start + count; i++) {
>> +		struct vb2_buffer *vb = vb2_get_buffer(q, i);
>> +
>> +		if (!vb) {
>> +			ret = -EINVAL;
>> +			goto unlock;
>> +		}
>> +		if (vb->state != VB2_BUF_STATE_DEQUEUED) {
>> +			ret = -EBUSY;
>> +			goto unlock;
>> +		}
>> +	}
>> +	__vb2_queue_free(q, start, count);
>> +	dprintk(q, 2, "%u buffers removed\n", count);
>> +
>> +unlock:
>> +	mutex_unlock(&q->mmap_lock);
>> +	return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(vb2_core_remove_bufs);
>> +
>>  /*
>>   * vb2_start_streaming() - Attempt to start streaming.
>>   * @q:		videobuf2 queue
>> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>> index 03e8080a68a8..293f3d5f1c4e 100644
>> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
>> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>> @@ -685,7 +685,7 @@ static void vb2_set_flags_and_caps(struct vb2_queue *q, u32 memory,
>>  		*flags &= V4L2_MEMORY_FLAG_NON_COHERENT;
>>  	}
>>  
>> -	*caps = V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
>> +	*caps |= V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
>>  	if (q->io_modes & VB2_MMAP)
>>  		*caps |= V4L2_BUF_CAP_SUPPORTS_MMAP;
>>  	if (q->io_modes & VB2_USERPTR)
>> @@ -1001,6 +1001,24 @@ EXPORT_SYMBOL_GPL(vb2_poll);
>>  
>>  /* vb2 ioctl helpers */
>>  
>> +int vb2_ioctl_remove_bufs(struct file *file, void *priv,
>> +			  struct v4l2_remove_buffers *d)
>> +{
>> +	struct video_device *vdev = video_devdata(file);
>> +
>> +	if (vdev->queue->type != d->type)
>> +		return -EINVAL;
>> +
>> +	if (d->count == 0)
>> +		return 0;
>> +
>> +	if (vb2_queue_is_busy(vdev->queue, file))
>> +		return -EBUSY;
>> +
>> +	return vb2_core_remove_bufs(vdev->queue, d->index, d->count);
>> +}
>> +EXPORT_SYMBOL_GPL(vb2_ioctl_remove_bufs);
>> +
>>  int vb2_ioctl_reqbufs(struct file *file, void *priv,
>>  			  struct v4l2_requestbuffers *p)
>>  {
>> diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
>> index d13954bd31fd..e39e9742fdb5 100644
>> --- a/drivers/media/v4l2-core/v4l2-dev.c
>> +++ b/drivers/media/v4l2-core/v4l2-dev.c
>> @@ -722,6 +722,9 @@ static void determine_valid_ioctls(struct video_device *vdev)
>>  		SET_VALID_IOCTL(ops, VIDIOC_PREPARE_BUF, vidioc_prepare_buf);
>>  		SET_VALID_IOCTL(ops, VIDIOC_STREAMON, vidioc_streamon);
>>  		SET_VALID_IOCTL(ops, VIDIOC_STREAMOFF, vidioc_streamoff);
>> +		/* VIDIOC_CREATE_BUFS support is mandatory to enable VIDIOC_REMOVE_BUFS */
>> +		if (ops->vidioc_create_bufs)
>> +			SET_VALID_IOCTL(ops, VIDIOC_REMOVE_BUFS, vidioc_remove_bufs);
>>  	}
>>  
>>  	if (is_vid || is_vbi || is_meta) {
>> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
>> index 6e7b8b682d13..5aeff5519407 100644
>> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
>> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
>> @@ -489,6 +489,14 @@ static void v4l_print_create_buffers(const void *arg, bool write_only)
>>  	v4l_print_format(&p->format, write_only);
>>  }
>>  
>> +static void v4l_print_remove_buffers(const void *arg, bool write_only)
>> +{
>> +	const struct v4l2_remove_buffers *p = arg;
>> +
>> +	pr_cont("type=%s, index=%u, count=%u\n",
>> +		prt_names(p->type, v4l2_type_names), p->index, p->count);
>> +}
>> +
>>  static void v4l_print_streamparm(const void *arg, bool write_only)
>>  {
>>  	const struct v4l2_streamparm *p = arg;
>> @@ -2092,6 +2100,7 @@ static int v4l_overlay(const struct v4l2_ioctl_ops *ops,
>>  static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,
>>  				struct file *file, void *fh, void *arg)
>>  {
>> +	struct video_device *vfd = video_devdata(file);
>>  	struct v4l2_requestbuffers *p = arg;
>>  	int ret = check_fmt(file, p->type);
>>  
>> @@ -2100,6 +2109,10 @@ static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,
>>  
>>  	memset_after(p, 0, flags);
>>  
>> +	p->capabilities = 0;
>> +	if (is_valid_ioctl(vfd, VIDIOC_REMOVE_BUFS))
>> +		p->capabilities = V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS;
>> +
>>  	return ops->vidioc_reqbufs(file, fh, p);
>>  }
>>  
>> @@ -2133,6 +2146,7 @@ static int v4l_dqbuf(const struct v4l2_ioctl_ops *ops,
>>  static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
>>  				struct file *file, void *fh, void *arg)
>>  {
>> +	struct video_device *vfd = video_devdata(file);
>>  	struct v4l2_create_buffers *create = arg;
>>  	int ret = check_fmt(file, create->format.type);
>>  
>> @@ -2143,6 +2157,10 @@ static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
>>  
>>  	v4l_sanitize_format(&create->format);
>>  
>> +	create->capabilities = 0;
>> +	if (is_valid_ioctl(vfd, VIDIOC_REMOVE_BUFS))
>> +		create->capabilities = V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS;
>> +
>>  	ret = ops->vidioc_create_bufs(file, fh, create);
>>  
>>  	if (create->format.type == V4L2_BUF_TYPE_VIDEO_CAPTURE ||
>> @@ -2161,6 +2179,17 @@ static int v4l_prepare_buf(const struct v4l2_ioctl_ops *ops,
>>  	return ret ? ret : ops->vidioc_prepare_buf(file, fh, b);
>>  }
>>  
>> +static int v4l_remove_bufs(const struct v4l2_ioctl_ops *ops,
>> +			   struct file *file, void *fh, void *arg)
>> +{
>> +	struct v4l2_remove_buffers *remove = arg;
>> +
>> +	if (ops->vidioc_remove_bufs)
>> +		return ops->vidioc_remove_bufs(file, fh, remove);
>> +
>> +	return -ENOTTY;
>> +}
>> +
>>  static int v4l_g_parm(const struct v4l2_ioctl_ops *ops,
>>  				struct file *file, void *fh, void *arg)
>>  {
>> @@ -2910,6 +2939,7 @@ static const struct v4l2_ioctl_info v4l2_ioctls[] = {
>>  	IOCTL_INFO(VIDIOC_ENUM_FREQ_BANDS, v4l_enum_freq_bands, v4l_print_freq_band, 0),
>>  	IOCTL_INFO(VIDIOC_DBG_G_CHIP_INFO, v4l_dbg_g_chip_info, v4l_print_dbg_chip_info, INFO_FL_CLEAR(v4l2_dbg_chip_info, match)),
>>  	IOCTL_INFO(VIDIOC_QUERY_EXT_CTRL, v4l_query_ext_ctrl, v4l_print_query_ext_ctrl, INFO_FL_CTRL | INFO_FL_CLEAR(v4l2_query_ext_ctrl, id)),
>> +	IOCTL_INFO(VIDIOC_REMOVE_BUFS, v4l_remove_bufs, v4l_print_remove_buffers, INFO_FL_PRIO | INFO_FL_QUEUE | INFO_FL_CLEAR(v4l2_remove_buffers, type)),
>>  };
>>  #define V4L2_IOCTLS ARRAY_SIZE(v4l2_ioctls)
>>  
>> diff --git a/include/media/v4l2-ioctl.h b/include/media/v4l2-ioctl.h
>> index edb733f21604..bdbb7e542321 100644
>> --- a/include/media/v4l2-ioctl.h
>> +++ b/include/media/v4l2-ioctl.h
>> @@ -163,6 +163,8 @@ struct v4l2_fh;
>>   *	:ref:`VIDIOC_CREATE_BUFS <vidioc_create_bufs>` ioctl
>>   * @vidioc_prepare_buf: pointer to the function that implements
>>   *	:ref:`VIDIOC_PREPARE_BUF <vidioc_prepare_buf>` ioctl
>> + * @vidioc_remove_bufs: pointer to the function that implements
>> + *	:ref:`VIDIOC_REMOVE_BUFS <vidioc_remove_bufs>` ioctl
>>   * @vidioc_overlay: pointer to the function that implements
>>   *	:ref:`VIDIOC_OVERLAY <vidioc_overlay>` ioctl
>>   * @vidioc_g_fbuf: pointer to the function that implements
>> @@ -422,6 +424,8 @@ struct v4l2_ioctl_ops {
>>  				  struct v4l2_create_buffers *b);
>>  	int (*vidioc_prepare_buf)(struct file *file, void *fh,
>>  				  struct v4l2_buffer *b);
>> +	int (*vidioc_remove_bufs)(struct file *file, void *fh,
>> +				  struct v4l2_remove_buffers *d);
>>  
>>  	int (*vidioc_overlay)(struct file *file, void *fh, unsigned int i);
>>  	int (*vidioc_g_fbuf)(struct file *file, void *fh,
>> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
>> index b9333e2c7797..955237ac503d 100644
>> --- a/include/media/videobuf2-core.h
>> +++ b/include/media/videobuf2-core.h
>> @@ -870,6 +870,16 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
>>   */
>>  int vb2_core_prepare_buf(struct vb2_queue *q, struct vb2_buffer *vb, void *pb);
>>  
>> +/**
>> + * vb2_core_remove_bufs() -
>> + * @q:		pointer to &struct vb2_queue with videobuf2 queue.
>> + * @start:	first index of the range of buffers to remove.
>> + * @count:	number of buffers to remove.
>> + *
>> + *  Return: returns zero on success; an error code otherwise.
>> + */
>> +int vb2_core_remove_bufs(struct vb2_queue *q, unsigned int start, unsigned int count);
>> +
>>  /**
>>   * vb2_core_qbuf() - Queue a buffer from userspace
>>   *
>> diff --git a/include/media/videobuf2-v4l2.h b/include/media/videobuf2-v4l2.h
>> index 5a845887850b..77ce8238ab30 100644
>> --- a/include/media/videobuf2-v4l2.h
>> +++ b/include/media/videobuf2-v4l2.h
>> @@ -334,6 +334,8 @@ int vb2_ioctl_streamon(struct file *file, void *priv, enum v4l2_buf_type i);
>>  int vb2_ioctl_streamoff(struct file *file, void *priv, enum v4l2_buf_type i);
>>  int vb2_ioctl_expbuf(struct file *file, void *priv,
>>  	struct v4l2_exportbuffer *p);
>> +int vb2_ioctl_remove_bufs(struct file *file, void *priv,
>> +			  struct v4l2_remove_buffers *p);
>>  
>>  /* struct v4l2_file_operations helpers */
>>  
>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>> index a8015e5e7fa4..2663213b76a4 100644
>> --- a/include/uapi/linux/videodev2.h
>> +++ b/include/uapi/linux/videodev2.h
>> @@ -1036,6 +1036,7 @@ struct v4l2_requestbuffers {
>>  #define V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF	(1 << 5)
>>  #define V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS		(1 << 6)
>>  #define V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS		(1 << 7)
>> +#define V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS		(1 << 8)
>>  
>>  /**
>>   * struct v4l2_plane - plane info for multi-planar buffers
>> @@ -2624,6 +2625,20 @@ struct v4l2_create_buffers {
>>  	__u32			reserved[5];
>>  };
>>  
>> +/**
>> + * struct v4l2_remove_buffers - VIDIOC_REMOVE_BUFS argument
>> + * @index:	the first buffer to be removed
>> + * @count:	number of buffers to removed
>> + * @type:	enum v4l2_buf_type
>> + * @reserved:	future extensions
>> + */
>> +struct v4l2_remove_buffers {
>> +	__u32			index;
>> +	__u32			count;
>> +	__u32			type;
>> +	__u32			reserved[13];
>> +};
>> +
>>  /*
>>   *	I O C T L   C O D E S   F O R   V I D E O   D E V I C E S
>>   *
>> @@ -2723,6 +2738,8 @@ struct v4l2_create_buffers {
>>  #define VIDIOC_DBG_G_CHIP_INFO  _IOWR('V', 102, struct v4l2_dbg_chip_info)
>>  
>>  #define VIDIOC_QUERY_EXT_CTRL	_IOWR('V', 103, struct v4l2_query_ext_ctrl)
>> +#define VIDIOC_REMOVE_BUFS	_IOWR('V', 104, struct v4l2_remove_buffers)
>> +
>>  
>>  /* Reminder: when adding new ioctls please add support for them to
>>     drivers/media/v4l2-core/v4l2-compat-ioctl32.c as well! */
> 
> 
> 
> Thanks,
> Mauro

Em Thu, 21 Mar 2024 15:24:43 +0100
Hans Verkuil <hverkuil-cisco@xs4all.nl> escreveu:

> On 21/03/2024 3:14 pm, Mauro Carvalho Chehab wrote:
> > Em Thu, 14 Mar 2024 16:32:24 +0100
> > Benjamin Gaignard <benjamin.gaignard@collabora.com> escreveu:
> >   
> >> VIDIOC_REMOVE_BUFS ioctl allows to remove buffers from a queue.
> >> The number of buffers to remove in given by count field of
> >> struct v4l2_remove_buffers and the range start at the index
> >> specified in the same structure.
> >>
> >> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
> >> ---
> >> changes in version 21:
> >> - Be more careful about checking remove_bufs type field vs queue type.
> >> - Add documentation about type checking error.
> >> - Always set capabilities flags field.
> >>
> >>  .../userspace-api/media/v4l/user-func.rst     |  1 +
> >>  .../media/v4l/vidioc-remove-bufs.rst          | 85 +++++++++++++++++++
> >>  .../media/v4l/vidioc-reqbufs.rst              |  1 +
> >>  .../media/common/videobuf2/videobuf2-core.c   | 38 +++++++++
> >>  .../media/common/videobuf2/videobuf2-v4l2.c   | 20 ++++-
> >>  drivers/media/v4l2-core/v4l2-dev.c            |  3 +
> >>  drivers/media/v4l2-core/v4l2-ioctl.c          | 30 +++++++
> >>  include/media/v4l2-ioctl.h                    |  4 +
> >>  include/media/videobuf2-core.h                | 10 +++
> >>  include/media/videobuf2-v4l2.h                |  2 +
> >>  include/uapi/linux/videodev2.h                | 17 ++++
> >>  11 files changed, 210 insertions(+), 1 deletion(-)
> >>  create mode 100644 Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst
> >>
> >> diff --git a/Documentation/userspace-api/media/v4l/user-func.rst b/Documentation/userspace-api/media/v4l/user-func.rst
> >> index 15ff0bf7bbe6..6f661138801c 100644
> >> --- a/Documentation/userspace-api/media/v4l/user-func.rst
> >> +++ b/Documentation/userspace-api/media/v4l/user-func.rst
> >> @@ -62,6 +62,7 @@ Function Reference
> >>      vidioc-query-dv-timings
> >>      vidioc-querystd
> >>      vidioc-reqbufs
> >> +    vidioc-remove-bufs
> >>      vidioc-s-hw-freq-seek
> >>      vidioc-streamon
> >>      vidioc-subdev-enum-frame-interval
> >> diff --git a/Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst b/Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst
> >> new file mode 100644
> >> index 000000000000..0cbc8c7313b7
> >> --- /dev/null
> >> +++ b/Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst
> >> @@ -0,0 +1,85 @@
> >> +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
> >> +.. c:namespace:: V4L
> >> +
> >> +.. _VIDIOC_REMOVE_BUFS:
> >> +
> >> +************************
> >> +ioctl VIDIOC_REMOVE_BUFS
> >> +************************
> >> +
> >> +Name
> >> +====
> >> +
> >> +VIDIOC_REMOVE_BUFS - Removes buffers from a queue
> >> +
> >> +Synopsis
> >> +========
> >> +
> >> +.. c:macro:: VIDIOC_REMOVE_BUFS
> >> +
> >> +``int ioctl(int fd, VIDIOC_REMOVE_BUFS, struct v4l2_remove_buffers *argp)``
> >> +
> >> +Arguments
> >> +=========
> >> +
> >> +``fd``
> >> +    File descriptor returned by :c:func:`open()`.
> >> +
> >> +``argp``
> >> +    Pointer to struct :c:type:`v4l2_remove_buffers`.
> >> +
> >> +Description
> >> +===========
> >> +
> >> +Applications can optionally call the :ref:`VIDIOC_REMOVE_BUFS` ioctl to
> >> +remove buffers from a queue.
> >> +:ref:`VIDIOC_CREATE_BUFS` ioctl support is mandatory to enable :ref:`VIDIOC_REMOVE_BUFS`.
> >> +This ioctl is available if the ``V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS`` capability
> >> +is set on the queue when :c:func:`VIDIOC_REQBUFS` or :c:func:`VIDIOC_CREATE_BUFS`
> >> +are invoked.
> >> +
> >> +.. c:type:: v4l2_remove_buffers
> >> +
> >> +.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
> >> +
> >> +.. flat-table:: struct v4l2_remove_buffers
> >> +    :header-rows:  0
> >> +    :stub-columns: 0
> >> +    :widths:       1 1 2
> >> +
> >> +    * - __u32
> >> +      - ``index``
> >> +      - The starting buffer index to remove. This field is ignored if count == 0.
> >> +    * - __u32
> >> +      - ``count``
> >> +      - The number of buffers to be removed with indices 'index' until 'index + count - 1'.
> >> +        All buffers in this range must be valid and in DEQUEUED state.
> >> +        :ref:`VIDIOC_REMOVE_BUFS` will always check the validity of ``type`, if it is
> >> +        invalid it returns ``EINVAL`` error code.
> >> +        If count is set to 0 :ref:`VIDIOC_REMOVE_BUFS` will do nothing and return 0.
> >> +    * - __u32
> >> +      - ``type``
> >> +      - Type of the stream or buffers, this is the same as the struct
> >> +	:c:type:`v4l2_format` ``type`` field. See
> >> +	:c:type:`v4l2_buf_type` for valid values.
> >> +    * - __u32
> >> +      - ``reserved``\ [13]
> >> +      - A place holder for future extensions. Drivers and applications
> >> +	must set the array to zero.
> >> +
> >> +Return Value
> >> +============
> >> +
> >> +On success 0 is returned, on error -1 and the ``errno`` variable is set
> >> +appropriately. The generic error codes are described at the
> >> +:ref:`Generic Error Codes <gen-errors>` chapter.  
> > 
> > It is not enough to just return an error code. it should also describe
> > what will be the expected behavior after the call. Something like:
> > 
> > 	If an error occurs, no buffers will be freed and one of the
> > 	error codes below will be returned:  
> 
> That's good to have. That is indeed not stated explicitly.
> 
> >   
> >> +
> >> +EBUSY
> >> +    File I/O is in progress.
> >> +    One or more of the buffers in the range ``index`` to ``index + count - 1`` are not
> >> +    in DEQUEUED state.
> >> +
> >> +EINVAL
> >> +    One or more of the buffers in the range ``index`` to ``index + count - 1`` do not
> >> +    exist in the queue.
> >> +    The buffer type (``type`` field) is not valid.  
> > 
> > IMO, it needs also another error code: as there's a minimal number of
> > buffers to be queued (let's say, 2), what happens if there are currently
> > 3 buffers allocated and an ioctl is called to free 2 buffers?
> > 
> > IMO, it shall return an error code and not free any buffers.  
> 
> Note the requirement that all buffers you want to remove have to be in dequeued
> state. So you can never remove buffers that are still in flight. An attempt to
> do that results in EBUSY.
> 
> So there is no need for an other error code.
> 
> > 
> > The best would be to return a code different than EINVAL. Maybe E2BIG?
> >   
> >> diff --git a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
> >> index 0b3a41a45d05..bbc22dd76032 100644
> >> --- a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
> >> +++ b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
> >> @@ -121,6 +121,7 @@ aborting or finishing any DMA in progress, an implicit
> >>  .. _V4L2-BUF-CAP-SUPPORTS-M2M-HOLD-CAPTURE-BUF:
> >>  .. _V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS:
> >>  .. _V4L2-BUF-CAP-SUPPORTS-MAX-NUM-BUFFERS:
> >> +.. _V4L2-BUF-CAP-SUPPORTS-REMOVE-BUFS:
> >>  
> >>  .. raw:: latex
> >>  
> >> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> >> index 009cea95d662..0b2b48e1b2df 100644
> >> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> >> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> >> @@ -1691,6 +1691,44 @@ int vb2_core_prepare_buf(struct vb2_queue *q, struct vb2_buffer *vb, void *pb)
> >>  }
> >>  EXPORT_SYMBOL_GPL(vb2_core_prepare_buf);
> >>  
> >> +int vb2_core_remove_bufs(struct vb2_queue *q, unsigned int start, unsigned int count)
> >> +{
> >> +	unsigned int i, ret = 0;
> >> +	unsigned int q_num_bufs = vb2_get_num_buffers(q);
> >> +
> >> +	if (count == 0)
> >> +		return 0;
> >> +
> >> +	if (count > q_num_bufs)
> >> +		return -EINVAL;  
> > 
> > It also needs:
> > 
> > 	if (q_num_bufs - count < q->min_reqbufs_allocation && q_num_bufs != count)
> > 		return <some error code>;
> > 
> > e. g. it shall not accept keeping, for instance, just one buffer allocated.  
> 
> That's perfectly fine. The min_reqbufs_allocation is specific to VIDIOC_REQBUFS
> (hence the name). If you use CREATE_BUFS/REMOVE_BUFS, then you are fully responsible
> for allocating and removing buffers.
> 
> This is something that was discussed in earlier revisions of this series.
> 
> It is actually rather ugly that REQBUFS does this, but we need to keep that behavior
> since that's how REQBUFS worked historically.
> 
> VIDIOC_CREATE_BUFS was never affected by this, so if you want to allocate N
> buffers with CREATE_BUFS, then you'll never get more than N buffers (you might get
> less, of course).

OK.

So, after doing the documentation change, feel free to add:

Reviewed-by: Mauro Carvalho Chehab <mchehab@kernel.org>

> 
> Regards,
> 
> 	Hans
> 
> >   
> >> +
> >> +	if (start > q->max_num_buffers - count)
> >> +		return -EINVAL;
> >> +
> >> +	mutex_lock(&q->mmap_lock);
> >> +
> >> +	/* Check that all buffers in the range exist */
> >> +	for (i = start; i < start + count; i++) {
> >> +		struct vb2_buffer *vb = vb2_get_buffer(q, i);
> >> +
> >> +		if (!vb) {
> >> +			ret = -EINVAL;
> >> +			goto unlock;
> >> +		}
> >> +		if (vb->state != VB2_BUF_STATE_DEQUEUED) {
> >> +			ret = -EBUSY;
> >> +			goto unlock;
> >> +		}
> >> +	}
> >> +	__vb2_queue_free(q, start, count);
> >> +	dprintk(q, 2, "%u buffers removed\n", count);
> >> +
> >> +unlock:
> >> +	mutex_unlock(&q->mmap_lock);
> >> +	return ret;
> >> +}
> >> +EXPORT_SYMBOL_GPL(vb2_core_remove_bufs);
> >> +
> >>  /*
> >>   * vb2_start_streaming() - Attempt to start streaming.
> >>   * @q:		videobuf2 queue
> >> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> >> index 03e8080a68a8..293f3d5f1c4e 100644
> >> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> >> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> >> @@ -685,7 +685,7 @@ static void vb2_set_flags_and_caps(struct vb2_queue *q, u32 memory,
> >>  		*flags &= V4L2_MEMORY_FLAG_NON_COHERENT;
> >>  	}
> >>  
> >> -	*caps = V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
> >> +	*caps |= V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
> >>  	if (q->io_modes & VB2_MMAP)
> >>  		*caps |= V4L2_BUF_CAP_SUPPORTS_MMAP;
> >>  	if (q->io_modes & VB2_USERPTR)
> >> @@ -1001,6 +1001,24 @@ EXPORT_SYMBOL_GPL(vb2_poll);
> >>  
> >>  /* vb2 ioctl helpers */
> >>  
> >> +int vb2_ioctl_remove_bufs(struct file *file, void *priv,
> >> +			  struct v4l2_remove_buffers *d)
> >> +{
> >> +	struct video_device *vdev = video_devdata(file);
> >> +
> >> +	if (vdev->queue->type != d->type)
> >> +		return -EINVAL;
> >> +
> >> +	if (d->count == 0)
> >> +		return 0;
> >> +
> >> +	if (vb2_queue_is_busy(vdev->queue, file))
> >> +		return -EBUSY;
> >> +
> >> +	return vb2_core_remove_bufs(vdev->queue, d->index, d->count);
> >> +}
> >> +EXPORT_SYMBOL_GPL(vb2_ioctl_remove_bufs);
> >> +
> >>  int vb2_ioctl_reqbufs(struct file *file, void *priv,
> >>  			  struct v4l2_requestbuffers *p)
> >>  {
> >> diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
> >> index d13954bd31fd..e39e9742fdb5 100644
> >> --- a/drivers/media/v4l2-core/v4l2-dev.c
> >> +++ b/drivers/media/v4l2-core/v4l2-dev.c
> >> @@ -722,6 +722,9 @@ static void determine_valid_ioctls(struct video_device *vdev)
> >>  		SET_VALID_IOCTL(ops, VIDIOC_PREPARE_BUF, vidioc_prepare_buf);
> >>  		SET_VALID_IOCTL(ops, VIDIOC_STREAMON, vidioc_streamon);
> >>  		SET_VALID_IOCTL(ops, VIDIOC_STREAMOFF, vidioc_streamoff);
> >> +		/* VIDIOC_CREATE_BUFS support is mandatory to enable VIDIOC_REMOVE_BUFS */
> >> +		if (ops->vidioc_create_bufs)
> >> +			SET_VALID_IOCTL(ops, VIDIOC_REMOVE_BUFS, vidioc_remove_bufs);
> >>  	}
> >>  
> >>  	if (is_vid || is_vbi || is_meta) {
> >> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> >> index 6e7b8b682d13..5aeff5519407 100644
> >> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> >> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> >> @@ -489,6 +489,14 @@ static void v4l_print_create_buffers(const void *arg, bool write_only)
> >>  	v4l_print_format(&p->format, write_only);
> >>  }
> >>  
> >> +static void v4l_print_remove_buffers(const void *arg, bool write_only)
> >> +{
> >> +	const struct v4l2_remove_buffers *p = arg;
> >> +
> >> +	pr_cont("type=%s, index=%u, count=%u\n",
> >> +		prt_names(p->type, v4l2_type_names), p->index, p->count);
> >> +}
> >> +
> >>  static void v4l_print_streamparm(const void *arg, bool write_only)
> >>  {
> >>  	const struct v4l2_streamparm *p = arg;
> >> @@ -2092,6 +2100,7 @@ static int v4l_overlay(const struct v4l2_ioctl_ops *ops,
> >>  static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,
> >>  				struct file *file, void *fh, void *arg)
> >>  {
> >> +	struct video_device *vfd = video_devdata(file);
> >>  	struct v4l2_requestbuffers *p = arg;
> >>  	int ret = check_fmt(file, p->type);
> >>  
> >> @@ -2100,6 +2109,10 @@ static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,
> >>  
> >>  	memset_after(p, 0, flags);
> >>  
> >> +	p->capabilities = 0;
> >> +	if (is_valid_ioctl(vfd, VIDIOC_REMOVE_BUFS))
> >> +		p->capabilities = V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS;
> >> +
> >>  	return ops->vidioc_reqbufs(file, fh, p);
> >>  }
> >>  
> >> @@ -2133,6 +2146,7 @@ static int v4l_dqbuf(const struct v4l2_ioctl_ops *ops,
> >>  static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
> >>  				struct file *file, void *fh, void *arg)
> >>  {
> >> +	struct video_device *vfd = video_devdata(file);
> >>  	struct v4l2_create_buffers *create = arg;
> >>  	int ret = check_fmt(file, create->format.type);
> >>  
> >> @@ -2143,6 +2157,10 @@ static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
> >>  
> >>  	v4l_sanitize_format(&create->format);
> >>  
> >> +	create->capabilities = 0;
> >> +	if (is_valid_ioctl(vfd, VIDIOC_REMOVE_BUFS))
> >> +		create->capabilities = V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS;
> >> +
> >>  	ret = ops->vidioc_create_bufs(file, fh, create);
> >>  
> >>  	if (create->format.type == V4L2_BUF_TYPE_VIDEO_CAPTURE ||
> >> @@ -2161,6 +2179,17 @@ static int v4l_prepare_buf(const struct v4l2_ioctl_ops *ops,
> >>  	return ret ? ret : ops->vidioc_prepare_buf(file, fh, b);
> >>  }
> >>  
> >> +static int v4l_remove_bufs(const struct v4l2_ioctl_ops *ops,
> >> +			   struct file *file, void *fh, void *arg)
> >> +{
> >> +	struct v4l2_remove_buffers *remove = arg;
> >> +
> >> +	if (ops->vidioc_remove_bufs)
> >> +		return ops->vidioc_remove_bufs(file, fh, remove);
> >> +
> >> +	return -ENOTTY;
> >> +}
> >> +
> >>  static int v4l_g_parm(const struct v4l2_ioctl_ops *ops,
> >>  				struct file *file, void *fh, void *arg)
> >>  {
> >> @@ -2910,6 +2939,7 @@ static const struct v4l2_ioctl_info v4l2_ioctls[] = {
> >>  	IOCTL_INFO(VIDIOC_ENUM_FREQ_BANDS, v4l_enum_freq_bands, v4l_print_freq_band, 0),
> >>  	IOCTL_INFO(VIDIOC_DBG_G_CHIP_INFO, v4l_dbg_g_chip_info, v4l_print_dbg_chip_info, INFO_FL_CLEAR(v4l2_dbg_chip_info, match)),
> >>  	IOCTL_INFO(VIDIOC_QUERY_EXT_CTRL, v4l_query_ext_ctrl, v4l_print_query_ext_ctrl, INFO_FL_CTRL | INFO_FL_CLEAR(v4l2_query_ext_ctrl, id)),
> >> +	IOCTL_INFO(VIDIOC_REMOVE_BUFS, v4l_remove_bufs, v4l_print_remove_buffers, INFO_FL_PRIO | INFO_FL_QUEUE | INFO_FL_CLEAR(v4l2_remove_buffers, type)),
> >>  };
> >>  #define V4L2_IOCTLS ARRAY_SIZE(v4l2_ioctls)
> >>  
> >> diff --git a/include/media/v4l2-ioctl.h b/include/media/v4l2-ioctl.h
> >> index edb733f21604..bdbb7e542321 100644
> >> --- a/include/media/v4l2-ioctl.h
> >> +++ b/include/media/v4l2-ioctl.h
> >> @@ -163,6 +163,8 @@ struct v4l2_fh;
> >>   *	:ref:`VIDIOC_CREATE_BUFS <vidioc_create_bufs>` ioctl
> >>   * @vidioc_prepare_buf: pointer to the function that implements
> >>   *	:ref:`VIDIOC_PREPARE_BUF <vidioc_prepare_buf>` ioctl
> >> + * @vidioc_remove_bufs: pointer to the function that implements
> >> + *	:ref:`VIDIOC_REMOVE_BUFS <vidioc_remove_bufs>` ioctl
> >>   * @vidioc_overlay: pointer to the function that implements
> >>   *	:ref:`VIDIOC_OVERLAY <vidioc_overlay>` ioctl
> >>   * @vidioc_g_fbuf: pointer to the function that implements
> >> @@ -422,6 +424,8 @@ struct v4l2_ioctl_ops {
> >>  				  struct v4l2_create_buffers *b);
> >>  	int (*vidioc_prepare_buf)(struct file *file, void *fh,
> >>  				  struct v4l2_buffer *b);
> >> +	int (*vidioc_remove_bufs)(struct file *file, void *fh,
> >> +				  struct v4l2_remove_buffers *d);
> >>  
> >>  	int (*vidioc_overlay)(struct file *file, void *fh, unsigned int i);
> >>  	int (*vidioc_g_fbuf)(struct file *file, void *fh,
> >> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> >> index b9333e2c7797..955237ac503d 100644
> >> --- a/include/media/videobuf2-core.h
> >> +++ b/include/media/videobuf2-core.h
> >> @@ -870,6 +870,16 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
> >>   */
> >>  int vb2_core_prepare_buf(struct vb2_queue *q, struct vb2_buffer *vb, void *pb);
> >>  
> >> +/**
> >> + * vb2_core_remove_bufs() -
> >> + * @q:		pointer to &struct vb2_queue with videobuf2 queue.
> >> + * @start:	first index of the range of buffers to remove.
> >> + * @count:	number of buffers to remove.
> >> + *
> >> + *  Return: returns zero on success; an error code otherwise.
> >> + */
> >> +int vb2_core_remove_bufs(struct vb2_queue *q, unsigned int start, unsigned int count);
> >> +
> >>  /**
> >>   * vb2_core_qbuf() - Queue a buffer from userspace
> >>   *
> >> diff --git a/include/media/videobuf2-v4l2.h b/include/media/videobuf2-v4l2.h
> >> index 5a845887850b..77ce8238ab30 100644
> >> --- a/include/media/videobuf2-v4l2.h
> >> +++ b/include/media/videobuf2-v4l2.h
> >> @@ -334,6 +334,8 @@ int vb2_ioctl_streamon(struct file *file, void *priv, enum v4l2_buf_type i);
> >>  int vb2_ioctl_streamoff(struct file *file, void *priv, enum v4l2_buf_type i);
> >>  int vb2_ioctl_expbuf(struct file *file, void *priv,
> >>  	struct v4l2_exportbuffer *p);
> >> +int vb2_ioctl_remove_bufs(struct file *file, void *priv,
> >> +			  struct v4l2_remove_buffers *p);
> >>  
> >>  /* struct v4l2_file_operations helpers */
> >>  
> >> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> >> index a8015e5e7fa4..2663213b76a4 100644
> >> --- a/include/uapi/linux/videodev2.h
> >> +++ b/include/uapi/linux/videodev2.h
> >> @@ -1036,6 +1036,7 @@ struct v4l2_requestbuffers {
> >>  #define V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF	(1 << 5)
> >>  #define V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS		(1 << 6)
> >>  #define V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS		(1 << 7)
> >> +#define V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS		(1 << 8)
> >>  
> >>  /**
> >>   * struct v4l2_plane - plane info for multi-planar buffers
> >> @@ -2624,6 +2625,20 @@ struct v4l2_create_buffers {
> >>  	__u32			reserved[5];
> >>  };
> >>  
> >> +/**
> >> + * struct v4l2_remove_buffers - VIDIOC_REMOVE_BUFS argument
> >> + * @index:	the first buffer to be removed
> >> + * @count:	number of buffers to removed
> >> + * @type:	enum v4l2_buf_type
> >> + * @reserved:	future extensions
> >> + */
> >> +struct v4l2_remove_buffers {
> >> +	__u32			index;
> >> +	__u32			count;
> >> +	__u32			type;
> >> +	__u32			reserved[13];
> >> +};
> >> +
> >>  /*
> >>   *	I O C T L   C O D E S   F O R   V I D E O   D E V I C E S
> >>   *
> >> @@ -2723,6 +2738,8 @@ struct v4l2_create_buffers {
> >>  #define VIDIOC_DBG_G_CHIP_INFO  _IOWR('V', 102, struct v4l2_dbg_chip_info)
> >>  
> >>  #define VIDIOC_QUERY_EXT_CTRL	_IOWR('V', 103, struct v4l2_query_ext_ctrl)
> >> +#define VIDIOC_REMOVE_BUFS	_IOWR('V', 104, struct v4l2_remove_buffers)
> >> +
> >>  
> >>  /* Reminder: when adding new ioctls please add support for them to
> >>     drivers/media/v4l2-core/v4l2-compat-ioctl32.c as well! */  
> > 
> > 
> > 
> > Thanks,
> > Mauro  
> 



Thanks,
Mauro

Hi Benjamin,

I added the one additional sentence to vidioc-remove-bufs.rst as suggested
by Mauro, and added his Reviewed/Acked-by lines.

I'll merge this series on Monday after 6.9-rc1 has been released and then
I will also merge the v4l-utils patches.

No need for you to do anything.

Thank you for all your work on this!

	Hans

On 21/03/2024 4:03 pm, Mauro Carvalho Chehab wrote:
> Em Thu, 21 Mar 2024 15:24:43 +0100
> Hans Verkuil <hverkuil-cisco@xs4all.nl> escreveu:
> 
>> On 21/03/2024 3:14 pm, Mauro Carvalho Chehab wrote:
>>> Em Thu, 14 Mar 2024 16:32:24 +0100
>>> Benjamin Gaignard <benjamin.gaignard@collabora.com> escreveu:
>>>   
>>>> VIDIOC_REMOVE_BUFS ioctl allows to remove buffers from a queue.
>>>> The number of buffers to remove in given by count field of
>>>> struct v4l2_remove_buffers and the range start at the index
>>>> specified in the same structure.
>>>>
>>>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
>>>> ---
>>>> changes in version 21:
>>>> - Be more careful about checking remove_bufs type field vs queue type.
>>>> - Add documentation about type checking error.
>>>> - Always set capabilities flags field.
>>>>
>>>>  .../userspace-api/media/v4l/user-func.rst     |  1 +
>>>>  .../media/v4l/vidioc-remove-bufs.rst          | 85 +++++++++++++++++++
>>>>  .../media/v4l/vidioc-reqbufs.rst              |  1 +
>>>>  .../media/common/videobuf2/videobuf2-core.c   | 38 +++++++++
>>>>  .../media/common/videobuf2/videobuf2-v4l2.c   | 20 ++++-
>>>>  drivers/media/v4l2-core/v4l2-dev.c            |  3 +
>>>>  drivers/media/v4l2-core/v4l2-ioctl.c          | 30 +++++++
>>>>  include/media/v4l2-ioctl.h                    |  4 +
>>>>  include/media/videobuf2-core.h                | 10 +++
>>>>  include/media/videobuf2-v4l2.h                |  2 +
>>>>  include/uapi/linux/videodev2.h                | 17 ++++
>>>>  11 files changed, 210 insertions(+), 1 deletion(-)
>>>>  create mode 100644 Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst
>>>>
>>>> diff --git a/Documentation/userspace-api/media/v4l/user-func.rst b/Documentation/userspace-api/media/v4l/user-func.rst
>>>> index 15ff0bf7bbe6..6f661138801c 100644
>>>> --- a/Documentation/userspace-api/media/v4l/user-func.rst
>>>> +++ b/Documentation/userspace-api/media/v4l/user-func.rst
>>>> @@ -62,6 +62,7 @@ Function Reference
>>>>      vidioc-query-dv-timings
>>>>      vidioc-querystd
>>>>      vidioc-reqbufs
>>>> +    vidioc-remove-bufs
>>>>      vidioc-s-hw-freq-seek
>>>>      vidioc-streamon
>>>>      vidioc-subdev-enum-frame-interval
>>>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst b/Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst
>>>> new file mode 100644
>>>> index 000000000000..0cbc8c7313b7
>>>> --- /dev/null
>>>> +++ b/Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst
>>>> @@ -0,0 +1,85 @@
>>>> +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
>>>> +.. c:namespace:: V4L
>>>> +
>>>> +.. _VIDIOC_REMOVE_BUFS:
>>>> +
>>>> +************************
>>>> +ioctl VIDIOC_REMOVE_BUFS
>>>> +************************
>>>> +
>>>> +Name
>>>> +====
>>>> +
>>>> +VIDIOC_REMOVE_BUFS - Removes buffers from a queue
>>>> +
>>>> +Synopsis
>>>> +========
>>>> +
>>>> +.. c:macro:: VIDIOC_REMOVE_BUFS
>>>> +
>>>> +``int ioctl(int fd, VIDIOC_REMOVE_BUFS, struct v4l2_remove_buffers *argp)``
>>>> +
>>>> +Arguments
>>>> +=========
>>>> +
>>>> +``fd``
>>>> +    File descriptor returned by :c:func:`open()`.
>>>> +
>>>> +``argp``
>>>> +    Pointer to struct :c:type:`v4l2_remove_buffers`.
>>>> +
>>>> +Description
>>>> +===========
>>>> +
>>>> +Applications can optionally call the :ref:`VIDIOC_REMOVE_BUFS` ioctl to
>>>> +remove buffers from a queue.
>>>> +:ref:`VIDIOC_CREATE_BUFS` ioctl support is mandatory to enable :ref:`VIDIOC_REMOVE_BUFS`.
>>>> +This ioctl is available if the ``V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS`` capability
>>>> +is set on the queue when :c:func:`VIDIOC_REQBUFS` or :c:func:`VIDIOC_CREATE_BUFS`
>>>> +are invoked.
>>>> +
>>>> +.. c:type:: v4l2_remove_buffers
>>>> +
>>>> +.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
>>>> +
>>>> +.. flat-table:: struct v4l2_remove_buffers
>>>> +    :header-rows:  0
>>>> +    :stub-columns: 0
>>>> +    :widths:       1 1 2
>>>> +
>>>> +    * - __u32
>>>> +      - ``index``
>>>> +      - The starting buffer index to remove. This field is ignored if count == 0.
>>>> +    * - __u32
>>>> +      - ``count``
>>>> +      - The number of buffers to be removed with indices 'index' until 'index + count - 1'.
>>>> +        All buffers in this range must be valid and in DEQUEUED state.
>>>> +        :ref:`VIDIOC_REMOVE_BUFS` will always check the validity of ``type`, if it is
>>>> +        invalid it returns ``EINVAL`` error code.
>>>> +        If count is set to 0 :ref:`VIDIOC_REMOVE_BUFS` will do nothing and return 0.
>>>> +    * - __u32
>>>> +      - ``type``
>>>> +      - Type of the stream or buffers, this is the same as the struct
>>>> +	:c:type:`v4l2_format` ``type`` field. See
>>>> +	:c:type:`v4l2_buf_type` for valid values.
>>>> +    * - __u32
>>>> +      - ``reserved``\ [13]
>>>> +      - A place holder for future extensions. Drivers and applications
>>>> +	must set the array to zero.
>>>> +
>>>> +Return Value
>>>> +============
>>>> +
>>>> +On success 0 is returned, on error -1 and the ``errno`` variable is set
>>>> +appropriately. The generic error codes are described at the
>>>> +:ref:`Generic Error Codes <gen-errors>` chapter.  
>>>
>>> It is not enough to just return an error code. it should also describe
>>> what will be the expected behavior after the call. Something like:
>>>
>>> 	If an error occurs, no buffers will be freed and one of the
>>> 	error codes below will be returned:  
>>
>> That's good to have. That is indeed not stated explicitly.
>>
>>>   
>>>> +
>>>> +EBUSY
>>>> +    File I/O is in progress.
>>>> +    One or more of the buffers in the range ``index`` to ``index + count - 1`` are not
>>>> +    in DEQUEUED state.
>>>> +
>>>> +EINVAL
>>>> +    One or more of the buffers in the range ``index`` to ``index + count - 1`` do not
>>>> +    exist in the queue.
>>>> +    The buffer type (``type`` field) is not valid.  
>>>
>>> IMO, it needs also another error code: as there's a minimal number of
>>> buffers to be queued (let's say, 2), what happens if there are currently
>>> 3 buffers allocated and an ioctl is called to free 2 buffers?
>>>
>>> IMO, it shall return an error code and not free any buffers.  
>>
>> Note the requirement that all buffers you want to remove have to be in dequeued
>> state. So you can never remove buffers that are still in flight. An attempt to
>> do that results in EBUSY.
>>
>> So there is no need for an other error code.
>>
>>>
>>> The best would be to return a code different than EINVAL. Maybe E2BIG?
>>>   
>>>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
>>>> index 0b3a41a45d05..bbc22dd76032 100644
>>>> --- a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
>>>> +++ b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
>>>> @@ -121,6 +121,7 @@ aborting or finishing any DMA in progress, an implicit
>>>>  .. _V4L2-BUF-CAP-SUPPORTS-M2M-HOLD-CAPTURE-BUF:
>>>>  .. _V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS:
>>>>  .. _V4L2-BUF-CAP-SUPPORTS-MAX-NUM-BUFFERS:
>>>> +.. _V4L2-BUF-CAP-SUPPORTS-REMOVE-BUFS:
>>>>  
>>>>  .. raw:: latex
>>>>  
>>>> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
>>>> index 009cea95d662..0b2b48e1b2df 100644
>>>> --- a/drivers/media/common/videobuf2/videobuf2-core.c
>>>> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
>>>> @@ -1691,6 +1691,44 @@ int vb2_core_prepare_buf(struct vb2_queue *q, struct vb2_buffer *vb, void *pb)
>>>>  }
>>>>  EXPORT_SYMBOL_GPL(vb2_core_prepare_buf);
>>>>  
>>>> +int vb2_core_remove_bufs(struct vb2_queue *q, unsigned int start, unsigned int count)
>>>> +{
>>>> +	unsigned int i, ret = 0;
>>>> +	unsigned int q_num_bufs = vb2_get_num_buffers(q);
>>>> +
>>>> +	if (count == 0)
>>>> +		return 0;
>>>> +
>>>> +	if (count > q_num_bufs)
>>>> +		return -EINVAL;  
>>>
>>> It also needs:
>>>
>>> 	if (q_num_bufs - count < q->min_reqbufs_allocation && q_num_bufs != count)
>>> 		return <some error code>;
>>>
>>> e. g. it shall not accept keeping, for instance, just one buffer allocated.  
>>
>> That's perfectly fine. The min_reqbufs_allocation is specific to VIDIOC_REQBUFS
>> (hence the name). If you use CREATE_BUFS/REMOVE_BUFS, then you are fully responsible
>> for allocating and removing buffers.
>>
>> This is something that was discussed in earlier revisions of this series.
>>
>> It is actually rather ugly that REQBUFS does this, but we need to keep that behavior
>> since that's how REQBUFS worked historically.
>>
>> VIDIOC_CREATE_BUFS was never affected by this, so if you want to allocate N
>> buffers with CREATE_BUFS, then you'll never get more than N buffers (you might get
>> less, of course).
> 
> OK.
> 
> So, after doing the documentation change, feel free to add:
> 
> Reviewed-by: Mauro Carvalho Chehab <mchehab@kernel.org>
> 
>>
>> Regards,
>>
>> 	Hans
>>
>>>   
>>>> +
>>>> +	if (start > q->max_num_buffers - count)
>>>> +		return -EINVAL;
>>>> +
>>>> +	mutex_lock(&q->mmap_lock);
>>>> +
>>>> +	/* Check that all buffers in the range exist */
>>>> +	for (i = start; i < start + count; i++) {
>>>> +		struct vb2_buffer *vb = vb2_get_buffer(q, i);
>>>> +
>>>> +		if (!vb) {
>>>> +			ret = -EINVAL;
>>>> +			goto unlock;
>>>> +		}
>>>> +		if (vb->state != VB2_BUF_STATE_DEQUEUED) {
>>>> +			ret = -EBUSY;
>>>> +			goto unlock;
>>>> +		}
>>>> +	}
>>>> +	__vb2_queue_free(q, start, count);
>>>> +	dprintk(q, 2, "%u buffers removed\n", count);
>>>> +
>>>> +unlock:
>>>> +	mutex_unlock(&q->mmap_lock);
>>>> +	return ret;
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(vb2_core_remove_bufs);
>>>> +
>>>>  /*
>>>>   * vb2_start_streaming() - Attempt to start streaming.
>>>>   * @q:		videobuf2 queue
>>>> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>>>> index 03e8080a68a8..293f3d5f1c4e 100644
>>>> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
>>>> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>>>> @@ -685,7 +685,7 @@ static void vb2_set_flags_and_caps(struct vb2_queue *q, u32 memory,
>>>>  		*flags &= V4L2_MEMORY_FLAG_NON_COHERENT;
>>>>  	}
>>>>  
>>>> -	*caps = V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
>>>> +	*caps |= V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
>>>>  	if (q->io_modes & VB2_MMAP)
>>>>  		*caps |= V4L2_BUF_CAP_SUPPORTS_MMAP;
>>>>  	if (q->io_modes & VB2_USERPTR)
>>>> @@ -1001,6 +1001,24 @@ EXPORT_SYMBOL_GPL(vb2_poll);
>>>>  
>>>>  /* vb2 ioctl helpers */
>>>>  
>>>> +int vb2_ioctl_remove_bufs(struct file *file, void *priv,
>>>> +			  struct v4l2_remove_buffers *d)
>>>> +{
>>>> +	struct video_device *vdev = video_devdata(file);
>>>> +
>>>> +	if (vdev->queue->type != d->type)
>>>> +		return -EINVAL;
>>>> +
>>>> +	if (d->count == 0)
>>>> +		return 0;
>>>> +
>>>> +	if (vb2_queue_is_busy(vdev->queue, file))
>>>> +		return -EBUSY;
>>>> +
>>>> +	return vb2_core_remove_bufs(vdev->queue, d->index, d->count);
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(vb2_ioctl_remove_bufs);
>>>> +
>>>>  int vb2_ioctl_reqbufs(struct file *file, void *priv,
>>>>  			  struct v4l2_requestbuffers *p)
>>>>  {
>>>> diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
>>>> index d13954bd31fd..e39e9742fdb5 100644
>>>> --- a/drivers/media/v4l2-core/v4l2-dev.c
>>>> +++ b/drivers/media/v4l2-core/v4l2-dev.c
>>>> @@ -722,6 +722,9 @@ static void determine_valid_ioctls(struct video_device *vdev)
>>>>  		SET_VALID_IOCTL(ops, VIDIOC_PREPARE_BUF, vidioc_prepare_buf);
>>>>  		SET_VALID_IOCTL(ops, VIDIOC_STREAMON, vidioc_streamon);
>>>>  		SET_VALID_IOCTL(ops, VIDIOC_STREAMOFF, vidioc_streamoff);
>>>> +		/* VIDIOC_CREATE_BUFS support is mandatory to enable VIDIOC_REMOVE_BUFS */
>>>> +		if (ops->vidioc_create_bufs)
>>>> +			SET_VALID_IOCTL(ops, VIDIOC_REMOVE_BUFS, vidioc_remove_bufs);
>>>>  	}
>>>>  
>>>>  	if (is_vid || is_vbi || is_meta) {
>>>> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
>>>> index 6e7b8b682d13..5aeff5519407 100644
>>>> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
>>>> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
>>>> @@ -489,6 +489,14 @@ static void v4l_print_create_buffers(const void *arg, bool write_only)
>>>>  	v4l_print_format(&p->format, write_only);
>>>>  }
>>>>  
>>>> +static void v4l_print_remove_buffers(const void *arg, bool write_only)
>>>> +{
>>>> +	const struct v4l2_remove_buffers *p = arg;
>>>> +
>>>> +	pr_cont("type=%s, index=%u, count=%u\n",
>>>> +		prt_names(p->type, v4l2_type_names), p->index, p->count);
>>>> +}
>>>> +
>>>>  static void v4l_print_streamparm(const void *arg, bool write_only)
>>>>  {
>>>>  	const struct v4l2_streamparm *p = arg;
>>>> @@ -2092,6 +2100,7 @@ static int v4l_overlay(const struct v4l2_ioctl_ops *ops,
>>>>  static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,
>>>>  				struct file *file, void *fh, void *arg)
>>>>  {
>>>> +	struct video_device *vfd = video_devdata(file);
>>>>  	struct v4l2_requestbuffers *p = arg;
>>>>  	int ret = check_fmt(file, p->type);
>>>>  
>>>> @@ -2100,6 +2109,10 @@ static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,
>>>>  
>>>>  	memset_after(p, 0, flags);
>>>>  
>>>> +	p->capabilities = 0;
>>>> +	if (is_valid_ioctl(vfd, VIDIOC_REMOVE_BUFS))
>>>> +		p->capabilities = V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS;
>>>> +
>>>>  	return ops->vidioc_reqbufs(file, fh, p);
>>>>  }
>>>>  
>>>> @@ -2133,6 +2146,7 @@ static int v4l_dqbuf(const struct v4l2_ioctl_ops *ops,
>>>>  static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
>>>>  				struct file *file, void *fh, void *arg)
>>>>  {
>>>> +	struct video_device *vfd = video_devdata(file);
>>>>  	struct v4l2_create_buffers *create = arg;
>>>>  	int ret = check_fmt(file, create->format.type);
>>>>  
>>>> @@ -2143,6 +2157,10 @@ static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
>>>>  
>>>>  	v4l_sanitize_format(&create->format);
>>>>  
>>>> +	create->capabilities = 0;
>>>> +	if (is_valid_ioctl(vfd, VIDIOC_REMOVE_BUFS))
>>>> +		create->capabilities = V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS;
>>>> +
>>>>  	ret = ops->vidioc_create_bufs(file, fh, create);
>>>>  
>>>>  	if (create->format.type == V4L2_BUF_TYPE_VIDEO_CAPTURE ||
>>>> @@ -2161,6 +2179,17 @@ static int v4l_prepare_buf(const struct v4l2_ioctl_ops *ops,
>>>>  	return ret ? ret : ops->vidioc_prepare_buf(file, fh, b);
>>>>  }
>>>>  
>>>> +static int v4l_remove_bufs(const struct v4l2_ioctl_ops *ops,
>>>> +			   struct file *file, void *fh, void *arg)
>>>> +{
>>>> +	struct v4l2_remove_buffers *remove = arg;
>>>> +
>>>> +	if (ops->vidioc_remove_bufs)
>>>> +		return ops->vidioc_remove_bufs(file, fh, remove);
>>>> +
>>>> +	return -ENOTTY;
>>>> +}
>>>> +
>>>>  static int v4l_g_parm(const struct v4l2_ioctl_ops *ops,
>>>>  				struct file *file, void *fh, void *arg)
>>>>  {
>>>> @@ -2910,6 +2939,7 @@ static const struct v4l2_ioctl_info v4l2_ioctls[] = {
>>>>  	IOCTL_INFO(VIDIOC_ENUM_FREQ_BANDS, v4l_enum_freq_bands, v4l_print_freq_band, 0),
>>>>  	IOCTL_INFO(VIDIOC_DBG_G_CHIP_INFO, v4l_dbg_g_chip_info, v4l_print_dbg_chip_info, INFO_FL_CLEAR(v4l2_dbg_chip_info, match)),
>>>>  	IOCTL_INFO(VIDIOC_QUERY_EXT_CTRL, v4l_query_ext_ctrl, v4l_print_query_ext_ctrl, INFO_FL_CTRL | INFO_FL_CLEAR(v4l2_query_ext_ctrl, id)),
>>>> +	IOCTL_INFO(VIDIOC_REMOVE_BUFS, v4l_remove_bufs, v4l_print_remove_buffers, INFO_FL_PRIO | INFO_FL_QUEUE | INFO_FL_CLEAR(v4l2_remove_buffers, type)),
>>>>  };
>>>>  #define V4L2_IOCTLS ARRAY_SIZE(v4l2_ioctls)
>>>>  
>>>> diff --git a/include/media/v4l2-ioctl.h b/include/media/v4l2-ioctl.h
>>>> index edb733f21604..bdbb7e542321 100644
>>>> --- a/include/media/v4l2-ioctl.h
>>>> +++ b/include/media/v4l2-ioctl.h
>>>> @@ -163,6 +163,8 @@ struct v4l2_fh;
>>>>   *	:ref:`VIDIOC_CREATE_BUFS <vidioc_create_bufs>` ioctl
>>>>   * @vidioc_prepare_buf: pointer to the function that implements
>>>>   *	:ref:`VIDIOC_PREPARE_BUF <vidioc_prepare_buf>` ioctl
>>>> + * @vidioc_remove_bufs: pointer to the function that implements
>>>> + *	:ref:`VIDIOC_REMOVE_BUFS <vidioc_remove_bufs>` ioctl
>>>>   * @vidioc_overlay: pointer to the function that implements
>>>>   *	:ref:`VIDIOC_OVERLAY <vidioc_overlay>` ioctl
>>>>   * @vidioc_g_fbuf: pointer to the function that implements
>>>> @@ -422,6 +424,8 @@ struct v4l2_ioctl_ops {
>>>>  				  struct v4l2_create_buffers *b);
>>>>  	int (*vidioc_prepare_buf)(struct file *file, void *fh,
>>>>  				  struct v4l2_buffer *b);
>>>> +	int (*vidioc_remove_bufs)(struct file *file, void *fh,
>>>> +				  struct v4l2_remove_buffers *d);
>>>>  
>>>>  	int (*vidioc_overlay)(struct file *file, void *fh, unsigned int i);
>>>>  	int (*vidioc_g_fbuf)(struct file *file, void *fh,
>>>> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
>>>> index b9333e2c7797..955237ac503d 100644
>>>> --- a/include/media/videobuf2-core.h
>>>> +++ b/include/media/videobuf2-core.h
>>>> @@ -870,6 +870,16 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
>>>>   */
>>>>  int vb2_core_prepare_buf(struct vb2_queue *q, struct vb2_buffer *vb, void *pb);
>>>>  
>>>> +/**
>>>> + * vb2_core_remove_bufs() -
>>>> + * @q:		pointer to &struct vb2_queue with videobuf2 queue.
>>>> + * @start:	first index of the range of buffers to remove.
>>>> + * @count:	number of buffers to remove.
>>>> + *
>>>> + *  Return: returns zero on success; an error code otherwise.
>>>> + */
>>>> +int vb2_core_remove_bufs(struct vb2_queue *q, unsigned int start, unsigned int count);
>>>> +
>>>>  /**
>>>>   * vb2_core_qbuf() - Queue a buffer from userspace
>>>>   *
>>>> diff --git a/include/media/videobuf2-v4l2.h b/include/media/videobuf2-v4l2.h
>>>> index 5a845887850b..77ce8238ab30 100644
>>>> --- a/include/media/videobuf2-v4l2.h
>>>> +++ b/include/media/videobuf2-v4l2.h
>>>> @@ -334,6 +334,8 @@ int vb2_ioctl_streamon(struct file *file, void *priv, enum v4l2_buf_type i);
>>>>  int vb2_ioctl_streamoff(struct file *file, void *priv, enum v4l2_buf_type i);
>>>>  int vb2_ioctl_expbuf(struct file *file, void *priv,
>>>>  	struct v4l2_exportbuffer *p);
>>>> +int vb2_ioctl_remove_bufs(struct file *file, void *priv,
>>>> +			  struct v4l2_remove_buffers *p);
>>>>  
>>>>  /* struct v4l2_file_operations helpers */
>>>>  
>>>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>>>> index a8015e5e7fa4..2663213b76a4 100644
>>>> --- a/include/uapi/linux/videodev2.h
>>>> +++ b/include/uapi/linux/videodev2.h
>>>> @@ -1036,6 +1036,7 @@ struct v4l2_requestbuffers {
>>>>  #define V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF	(1 << 5)
>>>>  #define V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS		(1 << 6)
>>>>  #define V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS		(1 << 7)
>>>> +#define V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS		(1 << 8)
>>>>  
>>>>  /**
>>>>   * struct v4l2_plane - plane info for multi-planar buffers
>>>> @@ -2624,6 +2625,20 @@ struct v4l2_create_buffers {
>>>>  	__u32			reserved[5];
>>>>  };
>>>>  
>>>> +/**
>>>> + * struct v4l2_remove_buffers - VIDIOC_REMOVE_BUFS argument
>>>> + * @index:	the first buffer to be removed
>>>> + * @count:	number of buffers to removed
>>>> + * @type:	enum v4l2_buf_type
>>>> + * @reserved:	future extensions
>>>> + */
>>>> +struct v4l2_remove_buffers {
>>>> +	__u32			index;
>>>> +	__u32			count;
>>>> +	__u32			type;
>>>> +	__u32			reserved[13];
>>>> +};
>>>> +
>>>>  /*
>>>>   *	I O C T L   C O D E S   F O R   V I D E O   D E V I C E S
>>>>   *
>>>> @@ -2723,6 +2738,8 @@ struct v4l2_create_buffers {
>>>>  #define VIDIOC_DBG_G_CHIP_INFO  _IOWR('V', 102, struct v4l2_dbg_chip_info)
>>>>  
>>>>  #define VIDIOC_QUERY_EXT_CTRL	_IOWR('V', 103, struct v4l2_query_ext_ctrl)
>>>> +#define VIDIOC_REMOVE_BUFS	_IOWR('V', 104, struct v4l2_remove_buffers)
>>>> +
>>>>  
>>>>  /* Reminder: when adding new ioctls please add support for them to
>>>>     drivers/media/v4l2-core/v4l2-compat-ioctl32.c as well! */  
>>>
>>>
>>>
>>> Thanks,
>>> Mauro  
>>
> 
> 
> 
> Thanks,
> Mauro
>

Le 22/03/2024 à 08:54, Hans Verkuil a écrit :
> Hi Benjamin,
>
> I added the one additional sentence to vidioc-remove-bufs.rst as suggested
> by Mauro, and added his Reviewed/Acked-by lines.
>
> I'll merge this series on Monday after 6.9-rc1 has been released and then
> I will also merge the v4l-utils patches.
>
> No need for you to do anything.
>
> Thank you for all your work on this!

I happy to see this been merge soon.
Thanks lot for your time and your review.

Regards,
Benjamin

>
> 	Hans
>
> On 21/03/2024 4:03 pm, Mauro Carvalho Chehab wrote:
>> Em Thu, 21 Mar 2024 15:24:43 +0100
>> Hans Verkuil <hverkuil-cisco@xs4all.nl> escreveu:
>>
>>> On 21/03/2024 3:14 pm, Mauro Carvalho Chehab wrote:
>>>> Em Thu, 14 Mar 2024 16:32:24 +0100
>>>> Benjamin Gaignard <benjamin.gaignard@collabora.com> escreveu:
>>>>    
>>>>> VIDIOC_REMOVE_BUFS ioctl allows to remove buffers from a queue.
>>>>> The number of buffers to remove in given by count field of
>>>>> struct v4l2_remove_buffers and the range start at the index
>>>>> specified in the same structure.
>>>>>
>>>>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
>>>>> ---
>>>>> changes in version 21:
>>>>> - Be more careful about checking remove_bufs type field vs queue type.
>>>>> - Add documentation about type checking error.
>>>>> - Always set capabilities flags field.
>>>>>
>>>>>   .../userspace-api/media/v4l/user-func.rst     |  1 +
>>>>>   .../media/v4l/vidioc-remove-bufs.rst          | 85 +++++++++++++++++++
>>>>>   .../media/v4l/vidioc-reqbufs.rst              |  1 +
>>>>>   .../media/common/videobuf2/videobuf2-core.c   | 38 +++++++++
>>>>>   .../media/common/videobuf2/videobuf2-v4l2.c   | 20 ++++-
>>>>>   drivers/media/v4l2-core/v4l2-dev.c            |  3 +
>>>>>   drivers/media/v4l2-core/v4l2-ioctl.c          | 30 +++++++
>>>>>   include/media/v4l2-ioctl.h                    |  4 +
>>>>>   include/media/videobuf2-core.h                | 10 +++
>>>>>   include/media/videobuf2-v4l2.h                |  2 +
>>>>>   include/uapi/linux/videodev2.h                | 17 ++++
>>>>>   11 files changed, 210 insertions(+), 1 deletion(-)
>>>>>   create mode 100644 Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst
>>>>>
>>>>> diff --git a/Documentation/userspace-api/media/v4l/user-func.rst b/Documentation/userspace-api/media/v4l/user-func.rst
>>>>> index 15ff0bf7bbe6..6f661138801c 100644
>>>>> --- a/Documentation/userspace-api/media/v4l/user-func.rst
>>>>> +++ b/Documentation/userspace-api/media/v4l/user-func.rst
>>>>> @@ -62,6 +62,7 @@ Function Reference
>>>>>       vidioc-query-dv-timings
>>>>>       vidioc-querystd
>>>>>       vidioc-reqbufs
>>>>> +    vidioc-remove-bufs
>>>>>       vidioc-s-hw-freq-seek
>>>>>       vidioc-streamon
>>>>>       vidioc-subdev-enum-frame-interval
>>>>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst b/Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst
>>>>> new file mode 100644
>>>>> index 000000000000..0cbc8c7313b7
>>>>> --- /dev/null
>>>>> +++ b/Documentation/userspace-api/media/v4l/vidioc-remove-bufs.rst
>>>>> @@ -0,0 +1,85 @@
>>>>> +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
>>>>> +.. c:namespace:: V4L
>>>>> +
>>>>> +.. _VIDIOC_REMOVE_BUFS:
>>>>> +
>>>>> +************************
>>>>> +ioctl VIDIOC_REMOVE_BUFS
>>>>> +************************
>>>>> +
>>>>> +Name
>>>>> +====
>>>>> +
>>>>> +VIDIOC_REMOVE_BUFS - Removes buffers from a queue
>>>>> +
>>>>> +Synopsis
>>>>> +========
>>>>> +
>>>>> +.. c:macro:: VIDIOC_REMOVE_BUFS
>>>>> +
>>>>> +``int ioctl(int fd, VIDIOC_REMOVE_BUFS, struct v4l2_remove_buffers *argp)``
>>>>> +
>>>>> +Arguments
>>>>> +=========
>>>>> +
>>>>> +``fd``
>>>>> +    File descriptor returned by :c:func:`open()`.
>>>>> +
>>>>> +``argp``
>>>>> +    Pointer to struct :c:type:`v4l2_remove_buffers`.
>>>>> +
>>>>> +Description
>>>>> +===========
>>>>> +
>>>>> +Applications can optionally call the :ref:`VIDIOC_REMOVE_BUFS` ioctl to
>>>>> +remove buffers from a queue.
>>>>> +:ref:`VIDIOC_CREATE_BUFS` ioctl support is mandatory to enable :ref:`VIDIOC_REMOVE_BUFS`.
>>>>> +This ioctl is available if the ``V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS`` capability
>>>>> +is set on the queue when :c:func:`VIDIOC_REQBUFS` or :c:func:`VIDIOC_CREATE_BUFS`
>>>>> +are invoked.
>>>>> +
>>>>> +.. c:type:: v4l2_remove_buffers
>>>>> +
>>>>> +.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
>>>>> +
>>>>> +.. flat-table:: struct v4l2_remove_buffers
>>>>> +    :header-rows:  0
>>>>> +    :stub-columns: 0
>>>>> +    :widths:       1 1 2
>>>>> +
>>>>> +    * - __u32
>>>>> +      - ``index``
>>>>> +      - The starting buffer index to remove. This field is ignored if count == 0.
>>>>> +    * - __u32
>>>>> +      - ``count``
>>>>> +      - The number of buffers to be removed with indices 'index' until 'index + count - 1'.
>>>>> +        All buffers in this range must be valid and in DEQUEUED state.
>>>>> +        :ref:`VIDIOC_REMOVE_BUFS` will always check the validity of ``type`, if it is
>>>>> +        invalid it returns ``EINVAL`` error code.
>>>>> +        If count is set to 0 :ref:`VIDIOC_REMOVE_BUFS` will do nothing and return 0.
>>>>> +    * - __u32
>>>>> +      - ``type``
>>>>> +      - Type of the stream or buffers, this is the same as the struct
>>>>> +	:c:type:`v4l2_format` ``type`` field. See
>>>>> +	:c:type:`v4l2_buf_type` for valid values.
>>>>> +    * - __u32
>>>>> +      - ``reserved``\ [13]
>>>>> +      - A place holder for future extensions. Drivers and applications
>>>>> +	must set the array to zero.
>>>>> +
>>>>> +Return Value
>>>>> +============
>>>>> +
>>>>> +On success 0 is returned, on error -1 and the ``errno`` variable is set
>>>>> +appropriately. The generic error codes are described at the
>>>>> +:ref:`Generic Error Codes <gen-errors>` chapter.
>>>> It is not enough to just return an error code. it should also describe
>>>> what will be the expected behavior after the call. Something like:
>>>>
>>>> 	If an error occurs, no buffers will be freed and one of the
>>>> 	error codes below will be returned:
>>> That's good to have. That is indeed not stated explicitly.
>>>
>>>>    
>>>>> +
>>>>> +EBUSY
>>>>> +    File I/O is in progress.
>>>>> +    One or more of the buffers in the range ``index`` to ``index + count - 1`` are not
>>>>> +    in DEQUEUED state.
>>>>> +
>>>>> +EINVAL
>>>>> +    One or more of the buffers in the range ``index`` to ``index + count - 1`` do not
>>>>> +    exist in the queue.
>>>>> +    The buffer type (``type`` field) is not valid.
>>>> IMO, it needs also another error code: as there's a minimal number of
>>>> buffers to be queued (let's say, 2), what happens if there are currently
>>>> 3 buffers allocated and an ioctl is called to free 2 buffers?
>>>>
>>>> IMO, it shall return an error code and not free any buffers.
>>> Note the requirement that all buffers you want to remove have to be in dequeued
>>> state. So you can never remove buffers that are still in flight. An attempt to
>>> do that results in EBUSY.
>>>
>>> So there is no need for an other error code.
>>>
>>>> The best would be to return a code different than EINVAL. Maybe E2BIG?
>>>>    
>>>>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
>>>>> index 0b3a41a45d05..bbc22dd76032 100644
>>>>> --- a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
>>>>> +++ b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
>>>>> @@ -121,6 +121,7 @@ aborting or finishing any DMA in progress, an implicit
>>>>>   .. _V4L2-BUF-CAP-SUPPORTS-M2M-HOLD-CAPTURE-BUF:
>>>>>   .. _V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS:
>>>>>   .. _V4L2-BUF-CAP-SUPPORTS-MAX-NUM-BUFFERS:
>>>>> +.. _V4L2-BUF-CAP-SUPPORTS-REMOVE-BUFS:
>>>>>   
>>>>>   .. raw:: latex
>>>>>   
>>>>> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
>>>>> index 009cea95d662..0b2b48e1b2df 100644
>>>>> --- a/drivers/media/common/videobuf2/videobuf2-core.c
>>>>> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
>>>>> @@ -1691,6 +1691,44 @@ int vb2_core_prepare_buf(struct vb2_queue *q, struct vb2_buffer *vb, void *pb)
>>>>>   }
>>>>>   EXPORT_SYMBOL_GPL(vb2_core_prepare_buf);
>>>>>   
>>>>> +int vb2_core_remove_bufs(struct vb2_queue *q, unsigned int start, unsigned int count)
>>>>> +{
>>>>> +	unsigned int i, ret = 0;
>>>>> +	unsigned int q_num_bufs = vb2_get_num_buffers(q);
>>>>> +
>>>>> +	if (count == 0)
>>>>> +		return 0;
>>>>> +
>>>>> +	if (count > q_num_bufs)
>>>>> +		return -EINVAL;
>>>> It also needs:
>>>>
>>>> 	if (q_num_bufs - count < q->min_reqbufs_allocation && q_num_bufs != count)
>>>> 		return <some error code>;
>>>>
>>>> e. g. it shall not accept keeping, for instance, just one buffer allocated.
>>> That's perfectly fine. The min_reqbufs_allocation is specific to VIDIOC_REQBUFS
>>> (hence the name). If you use CREATE_BUFS/REMOVE_BUFS, then you are fully responsible
>>> for allocating and removing buffers.
>>>
>>> This is something that was discussed in earlier revisions of this series.
>>>
>>> It is actually rather ugly that REQBUFS does this, but we need to keep that behavior
>>> since that's how REQBUFS worked historically.
>>>
>>> VIDIOC_CREATE_BUFS was never affected by this, so if you want to allocate N
>>> buffers with CREATE_BUFS, then you'll never get more than N buffers (you might get
>>> less, of course).
>> OK.
>>
>> So, after doing the documentation change, feel free to add:
>>
>> Reviewed-by: Mauro Carvalho Chehab <mchehab@kernel.org>
>>
>>> Regards,
>>>
>>> 	Hans
>>>
>>>>    
>>>>> +
>>>>> +	if (start > q->max_num_buffers - count)
>>>>> +		return -EINVAL;
>>>>> +
>>>>> +	mutex_lock(&q->mmap_lock);
>>>>> +
>>>>> +	/* Check that all buffers in the range exist */
>>>>> +	for (i = start; i < start + count; i++) {
>>>>> +		struct vb2_buffer *vb = vb2_get_buffer(q, i);
>>>>> +
>>>>> +		if (!vb) {
>>>>> +			ret = -EINVAL;
>>>>> +			goto unlock;
>>>>> +		}
>>>>> +		if (vb->state != VB2_BUF_STATE_DEQUEUED) {
>>>>> +			ret = -EBUSY;
>>>>> +			goto unlock;
>>>>> +		}
>>>>> +	}
>>>>> +	__vb2_queue_free(q, start, count);
>>>>> +	dprintk(q, 2, "%u buffers removed\n", count);
>>>>> +
>>>>> +unlock:
>>>>> +	mutex_unlock(&q->mmap_lock);
>>>>> +	return ret;
>>>>> +}
>>>>> +EXPORT_SYMBOL_GPL(vb2_core_remove_bufs);
>>>>> +
>>>>>   /*
>>>>>    * vb2_start_streaming() - Attempt to start streaming.
>>>>>    * @q:		videobuf2 queue
>>>>> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>>>>> index 03e8080a68a8..293f3d5f1c4e 100644
>>>>> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
>>>>> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>>>>> @@ -685,7 +685,7 @@ static void vb2_set_flags_and_caps(struct vb2_queue *q, u32 memory,
>>>>>   		*flags &= V4L2_MEMORY_FLAG_NON_COHERENT;
>>>>>   	}
>>>>>   
>>>>> -	*caps = V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
>>>>> +	*caps |= V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS;
>>>>>   	if (q->io_modes & VB2_MMAP)
>>>>>   		*caps |= V4L2_BUF_CAP_SUPPORTS_MMAP;
>>>>>   	if (q->io_modes & VB2_USERPTR)
>>>>> @@ -1001,6 +1001,24 @@ EXPORT_SYMBOL_GPL(vb2_poll);
>>>>>   
>>>>>   /* vb2 ioctl helpers */
>>>>>   
>>>>> +int vb2_ioctl_remove_bufs(struct file *file, void *priv,
>>>>> +			  struct v4l2_remove_buffers *d)
>>>>> +{
>>>>> +	struct video_device *vdev = video_devdata(file);
>>>>> +
>>>>> +	if (vdev->queue->type != d->type)
>>>>> +		return -EINVAL;
>>>>> +
>>>>> +	if (d->count == 0)
>>>>> +		return 0;
>>>>> +
>>>>> +	if (vb2_queue_is_busy(vdev->queue, file))
>>>>> +		return -EBUSY;
>>>>> +
>>>>> +	return vb2_core_remove_bufs(vdev->queue, d->index, d->count);
>>>>> +}
>>>>> +EXPORT_SYMBOL_GPL(vb2_ioctl_remove_bufs);
>>>>> +
>>>>>   int vb2_ioctl_reqbufs(struct file *file, void *priv,
>>>>>   			  struct v4l2_requestbuffers *p)
>>>>>   {
>>>>> diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
>>>>> index d13954bd31fd..e39e9742fdb5 100644
>>>>> --- a/drivers/media/v4l2-core/v4l2-dev.c
>>>>> +++ b/drivers/media/v4l2-core/v4l2-dev.c
>>>>> @@ -722,6 +722,9 @@ static void determine_valid_ioctls(struct video_device *vdev)
>>>>>   		SET_VALID_IOCTL(ops, VIDIOC_PREPARE_BUF, vidioc_prepare_buf);
>>>>>   		SET_VALID_IOCTL(ops, VIDIOC_STREAMON, vidioc_streamon);
>>>>>   		SET_VALID_IOCTL(ops, VIDIOC_STREAMOFF, vidioc_streamoff);
>>>>> +		/* VIDIOC_CREATE_BUFS support is mandatory to enable VIDIOC_REMOVE_BUFS */
>>>>> +		if (ops->vidioc_create_bufs)
>>>>> +			SET_VALID_IOCTL(ops, VIDIOC_REMOVE_BUFS, vidioc_remove_bufs);
>>>>>   	}
>>>>>   
>>>>>   	if (is_vid || is_vbi || is_meta) {
>>>>> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
>>>>> index 6e7b8b682d13..5aeff5519407 100644
>>>>> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
>>>>> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
>>>>> @@ -489,6 +489,14 @@ static void v4l_print_create_buffers(const void *arg, bool write_only)
>>>>>   	v4l_print_format(&p->format, write_only);
>>>>>   }
>>>>>   
>>>>> +static void v4l_print_remove_buffers(const void *arg, bool write_only)
>>>>> +{
>>>>> +	const struct v4l2_remove_buffers *p = arg;
>>>>> +
>>>>> +	pr_cont("type=%s, index=%u, count=%u\n",
>>>>> +		prt_names(p->type, v4l2_type_names), p->index, p->count);
>>>>> +}
>>>>> +
>>>>>   static void v4l_print_streamparm(const void *arg, bool write_only)
>>>>>   {
>>>>>   	const struct v4l2_streamparm *p = arg;
>>>>> @@ -2092,6 +2100,7 @@ static int v4l_overlay(const struct v4l2_ioctl_ops *ops,
>>>>>   static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,
>>>>>   				struct file *file, void *fh, void *arg)
>>>>>   {
>>>>> +	struct video_device *vfd = video_devdata(file);
>>>>>   	struct v4l2_requestbuffers *p = arg;
>>>>>   	int ret = check_fmt(file, p->type);
>>>>>   
>>>>> @@ -2100,6 +2109,10 @@ static int v4l_reqbufs(const struct v4l2_ioctl_ops *ops,
>>>>>   
>>>>>   	memset_after(p, 0, flags);
>>>>>   
>>>>> +	p->capabilities = 0;
>>>>> +	if (is_valid_ioctl(vfd, VIDIOC_REMOVE_BUFS))
>>>>> +		p->capabilities = V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS;
>>>>> +
>>>>>   	return ops->vidioc_reqbufs(file, fh, p);
>>>>>   }
>>>>>   
>>>>> @@ -2133,6 +2146,7 @@ static int v4l_dqbuf(const struct v4l2_ioctl_ops *ops,
>>>>>   static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
>>>>>   				struct file *file, void *fh, void *arg)
>>>>>   {
>>>>> +	struct video_device *vfd = video_devdata(file);
>>>>>   	struct v4l2_create_buffers *create = arg;
>>>>>   	int ret = check_fmt(file, create->format.type);
>>>>>   
>>>>> @@ -2143,6 +2157,10 @@ static int v4l_create_bufs(const struct v4l2_ioctl_ops *ops,
>>>>>   
>>>>>   	v4l_sanitize_format(&create->format);
>>>>>   
>>>>> +	create->capabilities = 0;
>>>>> +	if (is_valid_ioctl(vfd, VIDIOC_REMOVE_BUFS))
>>>>> +		create->capabilities = V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS;
>>>>> +
>>>>>   	ret = ops->vidioc_create_bufs(file, fh, create);
>>>>>   
>>>>>   	if (create->format.type == V4L2_BUF_TYPE_VIDEO_CAPTURE ||
>>>>> @@ -2161,6 +2179,17 @@ static int v4l_prepare_buf(const struct v4l2_ioctl_ops *ops,
>>>>>   	return ret ? ret : ops->vidioc_prepare_buf(file, fh, b);
>>>>>   }
>>>>>   
>>>>> +static int v4l_remove_bufs(const struct v4l2_ioctl_ops *ops,
>>>>> +			   struct file *file, void *fh, void *arg)
>>>>> +{
>>>>> +	struct v4l2_remove_buffers *remove = arg;
>>>>> +
>>>>> +	if (ops->vidioc_remove_bufs)
>>>>> +		return ops->vidioc_remove_bufs(file, fh, remove);
>>>>> +
>>>>> +	return -ENOTTY;
>>>>> +}
>>>>> +
>>>>>   static int v4l_g_parm(const struct v4l2_ioctl_ops *ops,
>>>>>   				struct file *file, void *fh, void *arg)
>>>>>   {
>>>>> @@ -2910,6 +2939,7 @@ static const struct v4l2_ioctl_info v4l2_ioctls[] = {
>>>>>   	IOCTL_INFO(VIDIOC_ENUM_FREQ_BANDS, v4l_enum_freq_bands, v4l_print_freq_band, 0),
>>>>>   	IOCTL_INFO(VIDIOC_DBG_G_CHIP_INFO, v4l_dbg_g_chip_info, v4l_print_dbg_chip_info, INFO_FL_CLEAR(v4l2_dbg_chip_info, match)),
>>>>>   	IOCTL_INFO(VIDIOC_QUERY_EXT_CTRL, v4l_query_ext_ctrl, v4l_print_query_ext_ctrl, INFO_FL_CTRL | INFO_FL_CLEAR(v4l2_query_ext_ctrl, id)),
>>>>> +	IOCTL_INFO(VIDIOC_REMOVE_BUFS, v4l_remove_bufs, v4l_print_remove_buffers, INFO_FL_PRIO | INFO_FL_QUEUE | INFO_FL_CLEAR(v4l2_remove_buffers, type)),
>>>>>   };
>>>>>   #define V4L2_IOCTLS ARRAY_SIZE(v4l2_ioctls)
>>>>>   
>>>>> diff --git a/include/media/v4l2-ioctl.h b/include/media/v4l2-ioctl.h
>>>>> index edb733f21604..bdbb7e542321 100644
>>>>> --- a/include/media/v4l2-ioctl.h
>>>>> +++ b/include/media/v4l2-ioctl.h
>>>>> @@ -163,6 +163,8 @@ struct v4l2_fh;
>>>>>    *	:ref:`VIDIOC_CREATE_BUFS <vidioc_create_bufs>` ioctl
>>>>>    * @vidioc_prepare_buf: pointer to the function that implements
>>>>>    *	:ref:`VIDIOC_PREPARE_BUF <vidioc_prepare_buf>` ioctl
>>>>> + * @vidioc_remove_bufs: pointer to the function that implements
>>>>> + *	:ref:`VIDIOC_REMOVE_BUFS <vidioc_remove_bufs>` ioctl
>>>>>    * @vidioc_overlay: pointer to the function that implements
>>>>>    *	:ref:`VIDIOC_OVERLAY <vidioc_overlay>` ioctl
>>>>>    * @vidioc_g_fbuf: pointer to the function that implements
>>>>> @@ -422,6 +424,8 @@ struct v4l2_ioctl_ops {
>>>>>   				  struct v4l2_create_buffers *b);
>>>>>   	int (*vidioc_prepare_buf)(struct file *file, void *fh,
>>>>>   				  struct v4l2_buffer *b);
>>>>> +	int (*vidioc_remove_bufs)(struct file *file, void *fh,
>>>>> +				  struct v4l2_remove_buffers *d);
>>>>>   
>>>>>   	int (*vidioc_overlay)(struct file *file, void *fh, unsigned int i);
>>>>>   	int (*vidioc_g_fbuf)(struct file *file, void *fh,
>>>>> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
>>>>> index b9333e2c7797..955237ac503d 100644
>>>>> --- a/include/media/videobuf2-core.h
>>>>> +++ b/include/media/videobuf2-core.h
>>>>> @@ -870,6 +870,16 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
>>>>>    */
>>>>>   int vb2_core_prepare_buf(struct vb2_queue *q, struct vb2_buffer *vb, void *pb);
>>>>>   
>>>>> +/**
>>>>> + * vb2_core_remove_bufs() -
>>>>> + * @q:		pointer to &struct vb2_queue with videobuf2 queue.
>>>>> + * @start:	first index of the range of buffers to remove.
>>>>> + * @count:	number of buffers to remove.
>>>>> + *
>>>>> + *  Return: returns zero on success; an error code otherwise.
>>>>> + */
>>>>> +int vb2_core_remove_bufs(struct vb2_queue *q, unsigned int start, unsigned int count);
>>>>> +
>>>>>   /**
>>>>>    * vb2_core_qbuf() - Queue a buffer from userspace
>>>>>    *
>>>>> diff --git a/include/media/videobuf2-v4l2.h b/include/media/videobuf2-v4l2.h
>>>>> index 5a845887850b..77ce8238ab30 100644
>>>>> --- a/include/media/videobuf2-v4l2.h
>>>>> +++ b/include/media/videobuf2-v4l2.h
>>>>> @@ -334,6 +334,8 @@ int vb2_ioctl_streamon(struct file *file, void *priv, enum v4l2_buf_type i);
>>>>>   int vb2_ioctl_streamoff(struct file *file, void *priv, enum v4l2_buf_type i);
>>>>>   int vb2_ioctl_expbuf(struct file *file, void *priv,
>>>>>   	struct v4l2_exportbuffer *p);
>>>>> +int vb2_ioctl_remove_bufs(struct file *file, void *priv,
>>>>> +			  struct v4l2_remove_buffers *p);
>>>>>   
>>>>>   /* struct v4l2_file_operations helpers */
>>>>>   
>>>>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>>>>> index a8015e5e7fa4..2663213b76a4 100644
>>>>> --- a/include/uapi/linux/videodev2.h
>>>>> +++ b/include/uapi/linux/videodev2.h
>>>>> @@ -1036,6 +1036,7 @@ struct v4l2_requestbuffers {
>>>>>   #define V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF	(1 << 5)
>>>>>   #define V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS		(1 << 6)
>>>>>   #define V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS		(1 << 7)
>>>>> +#define V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS		(1 << 8)
>>>>>   
>>>>>   /**
>>>>>    * struct v4l2_plane - plane info for multi-planar buffers
>>>>> @@ -2624,6 +2625,20 @@ struct v4l2_create_buffers {
>>>>>   	__u32			reserved[5];
>>>>>   };
>>>>>   
>>>>> +/**
>>>>> + * struct v4l2_remove_buffers - VIDIOC_REMOVE_BUFS argument
>>>>> + * @index:	the first buffer to be removed
>>>>> + * @count:	number of buffers to removed
>>>>> + * @type:	enum v4l2_buf_type
>>>>> + * @reserved:	future extensions
>>>>> + */
>>>>> +struct v4l2_remove_buffers {
>>>>> +	__u32			index;
>>>>> +	__u32			count;
>>>>> +	__u32			type;
>>>>> +	__u32			reserved[13];
>>>>> +};
>>>>> +
>>>>>   /*
>>>>>    *	I O C T L   C O D E S   F O R   V I D E O   D E V I C E S
>>>>>    *
>>>>> @@ -2723,6 +2738,8 @@ struct v4l2_create_buffers {
>>>>>   #define VIDIOC_DBG_G_CHIP_INFO  _IOWR('V', 102, struct v4l2_dbg_chip_info)
>>>>>   
>>>>>   #define VIDIOC_QUERY_EXT_CTRL	_IOWR('V', 103, struct v4l2_query_ext_ctrl)
>>>>> +#define VIDIOC_REMOVE_BUFS	_IOWR('V', 104, struct v4l2_remove_buffers)
>>>>> +
>>>>>   
>>>>>   /* Reminder: when adding new ioctls please add support for them to
>>>>>      drivers/media/v4l2-core/v4l2-compat-ioctl32.c as well! */
>>>>
>>>>
>>>> Thanks,
>>>> Mauro
>>
>>
>> Thanks,
>> Mauro
>>
>