[RFC] media/doc: Allow sizeimage to be set by v4l clients

Message ID 20190116123701.10344-1-stanimir.varbanov@linaro.org
State New
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  • [RFC] media/doc: Allow sizeimage to be set by v4l clients
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Commit Message

Stanimir Varbanov Jan. 16, 2019, 12:37 p.m.
This changes v4l2_pix_format and v4l2_plane_pix_format sizeimage
field description to allow v4l clients to set bigger image size
in case of variable length compressed data.

Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>

---
 Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst | 5 ++++-
 Documentation/media/uapi/v4l/pixfmt-v4l2.rst        | 3 ++-
 2 files changed, 6 insertions(+), 2 deletions(-)

-- 
2.17.1

Comments

Stanimir Varbanov Jan. 21, 2019, 10:48 a.m. | #1
Hi Hans,

On 1/18/19 11:13 AM, Hans Verkuil wrote:
> On 1/16/19 1:37 PM, Stanimir Varbanov wrote:

>> This changes v4l2_pix_format and v4l2_plane_pix_format sizeimage

>> field description to allow v4l clients to set bigger image size

>> in case of variable length compressed data.

>>

>> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>

>> ---

>>  Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst | 5 ++++-

>>  Documentation/media/uapi/v4l/pixfmt-v4l2.rst        | 3 ++-

>>  2 files changed, 6 insertions(+), 2 deletions(-)

>>

>> diff --git a/Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst b/Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst

>> index 7f82dad9013a..dbe0b74e9ba4 100644

>> --- a/Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst

>> +++ b/Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst

>> @@ -30,7 +30,10 @@ describing all planes of that format.

>>  

>>      * - __u32

>>        - ``sizeimage``

>> -      - Maximum size in bytes required for image data in this plane.

>> +      - Maximum size in bytes required for image data in this plane,

>> +        set by the driver. When the image consists of variable length

>> +        compressed data this is the maximum number of bytes required

>> +        to hold an image, and it is allowed to be set by the client.

>>      * - __u32

>>        - ``bytesperline``

>>        - Distance in bytes between the leftmost pixels in two adjacent

>> diff --git a/Documentation/media/uapi/v4l/pixfmt-v4l2.rst b/Documentation/media/uapi/v4l/pixfmt-v4l2.rst

>> index 71eebfc6d853..54b6d2b67bd7 100644

>> --- a/Documentation/media/uapi/v4l/pixfmt-v4l2.rst

>> +++ b/Documentation/media/uapi/v4l/pixfmt-v4l2.rst

>> @@ -89,7 +89,8 @@ Single-planar format structure

>>        - Size in bytes of the buffer to hold a complete image, set by the

>>  	driver. Usually this is ``bytesperline`` times ``height``. When

>>  	the image consists of variable length compressed data this is the

>> -	maximum number of bytes required to hold an image.

>> +	maximum number of bytes required to hold an image, and it is

>> +	allowed to be set by the client.

>>      * - __u32

>>        - ``colorspace``

>>        - Image colorspace, from enum :c:type:`v4l2_colorspace`.

>>

> 

> Hmm. "maximum number of bytes required to hold an image": that's not actually true

> for bitstream formats like MPEG. It's just the size of the buffer used to store the

> bitstream, i.e. one buffer may actually contain multiple compressed images, or a

> compressed image is split over multiple buffers.

> 


Do you want me to change something in the current documentation, i.e.
the quoted above?

> Only for MJPEG is this statement true since each buffer will contain a single

> compressed JPEG image.

> 

> Regards,

> 

> 	Hans

> 


-- 
regards,
Stan
Stanimir Varbanov April 10, 2019, 2:52 p.m. | #2
On 4/10/19 5:39 PM, Hans Verkuil wrote:
> On 4/10/19 4:21 PM, Stanimir Varbanov wrote:

>> Hi Hans,

>>

>> On 3/14/19 3:11 PM, Hans Verkuil wrote:

>>> On 1/21/19 11:48 AM, Stanimir Varbanov wrote:

>>>> Hi Hans,

>>>>

>>>> On 1/18/19 11:13 AM, Hans Verkuil wrote:

>>>>> On 1/16/19 1:37 PM, Stanimir Varbanov wrote:

>>>>>> This changes v4l2_pix_format and v4l2_plane_pix_format sizeimage

>>>>>> field description to allow v4l clients to set bigger image size

>>>>>> in case of variable length compressed data.

>>>>>>

>>>>>> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>

>>>>>> ---

>>>>>>  Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst | 5 ++++-

>>>>>>  Documentation/media/uapi/v4l/pixfmt-v4l2.rst        | 3 ++-

>>>>>>  2 files changed, 6 insertions(+), 2 deletions(-)

>>>>>>

>>>>>> diff --git a/Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst b/Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst

>>>>>> index 7f82dad9013a..dbe0b74e9ba4 100644

>>>>>> --- a/Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst

>>>>>> +++ b/Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst

>>>>>> @@ -30,7 +30,10 @@ describing all planes of that format.

>>>>>>  

>>>>>>      * - __u32

>>>>>>        - ``sizeimage``

>>>>>> -      - Maximum size in bytes required for image data in this plane.

>>>>>> +      - Maximum size in bytes required for image data in this plane,

>>>>>> +        set by the driver. When the image consists of variable length

>>>>>> +        compressed data this is the maximum number of bytes required

>>>>>> +        to hold an image, and it is allowed to be set by the client.

>>>>>>      * - __u32

>>>>>>        - ``bytesperline``

>>>>>>        - Distance in bytes between the leftmost pixels in two adjacent

>>>>>> diff --git a/Documentation/media/uapi/v4l/pixfmt-v4l2.rst b/Documentation/media/uapi/v4l/pixfmt-v4l2.rst

>>>>>> index 71eebfc6d853..54b6d2b67bd7 100644

>>>>>> --- a/Documentation/media/uapi/v4l/pixfmt-v4l2.rst

>>>>>> +++ b/Documentation/media/uapi/v4l/pixfmt-v4l2.rst

>>>>>> @@ -89,7 +89,8 @@ Single-planar format structure

>>>>>>        - Size in bytes of the buffer to hold a complete image, set by the

>>>>>>  	driver. Usually this is ``bytesperline`` times ``height``. When

>>>>>>  	the image consists of variable length compressed data this is the

>>>>>> -	maximum number of bytes required to hold an image.

>>>>>> +	maximum number of bytes required to hold an image, and it is

>>>>>> +	allowed to be set by the client.

>>>>>>      * - __u32

>>>>>>        - ``colorspace``

>>>>>>        - Image colorspace, from enum :c:type:`v4l2_colorspace`.

>>>>>>

>>>>>

>>>>> Hmm. "maximum number of bytes required to hold an image": that's not actually true

>>>>> for bitstream formats like MPEG. It's just the size of the buffer used to store the

>>>>> bitstream, i.e. one buffer may actually contain multiple compressed images, or a

>>>>> compressed image is split over multiple buffers.

>>>>>

>>>>

>>>> Do you want me to change something in the current documentation, i.e.

>>>> the quoted above?

>>>

>>> Hmm, it looks like this discussion stalled (i.e. I forgot to reply).

>>>

>>> How about this:

>>>

>>> "When the image consists of variable length compressed data this is the

>>> number of bytes required by the encoder to support the worst-case

>>

>> I don't think 'encoder' is the right word here:

>>

>> s/encoder/encoder or decoder

> 

> or perhaps just 'codec'? Either is fine by me.


OK, then just 'codec'.

> 

>>

>>> compression scenario. Clients are allowed to set this field. However,

>>> drivers may ignore the value or modify it."

>>

>> Can we rephrase to:

>>

>> "Clients are allowed to set sizeimage field, but however drivers my

>> ignore the value or modify it."

>>

> 

> How about this:

> 

> "Clients are allowed to set the sizeimage field, but drivers may

>  modify it."


I'm fine with that.

I'll send with those changes and as regular patch. Thanks!

> 

> 'ignore the value' isn't right, since that suggests that the sizeimage

> value that is returned may not be in actual use. Since sizeimage can now

> be set by userspace, this means that a sanity check is needed in drivers

> as well (i.e. what if userspace sets sizeimage to ~0?)

> 

> This should be tested in v4l2-compliance as well.

> 

> Regards,

> 

> 	Hans

> 


-- 
regards,
Stan

Patch

diff --git a/Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst b/Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst
index 7f82dad9013a..dbe0b74e9ba4 100644
--- a/Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst
+++ b/Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst
@@ -30,7 +30,10 @@  describing all planes of that format.
 
     * - __u32
       - ``sizeimage``
-      - Maximum size in bytes required for image data in this plane.
+      - Maximum size in bytes required for image data in this plane,
+        set by the driver. When the image consists of variable length
+        compressed data this is the maximum number of bytes required
+        to hold an image, and it is allowed to be set by the client.
     * - __u32
       - ``bytesperline``
       - Distance in bytes between the leftmost pixels in two adjacent
diff --git a/Documentation/media/uapi/v4l/pixfmt-v4l2.rst b/Documentation/media/uapi/v4l/pixfmt-v4l2.rst
index 71eebfc6d853..54b6d2b67bd7 100644
--- a/Documentation/media/uapi/v4l/pixfmt-v4l2.rst
+++ b/Documentation/media/uapi/v4l/pixfmt-v4l2.rst
@@ -89,7 +89,8 @@  Single-planar format structure
       - Size in bytes of the buffer to hold a complete image, set by the
 	driver. Usually this is ``bytesperline`` times ``height``. When
 	the image consists of variable length compressed data this is the
-	maximum number of bytes required to hold an image.
+	maximum number of bytes required to hold an image, and it is
+	allowed to be set by the client.
     * - __u32
       - ``colorspace``
       - Image colorspace, from enum :c:type:`v4l2_colorspace`.