@@ -105,7 +105,15 @@ struct uvc_video {
bool is_enabled; /* tracks whether video stream is enabled */
unsigned int req_size;
struct list_head ureqs; /* all uvc_requests allocated by uvc_video */
+
+ /* USB requests that the video pump thread can encode into */
struct list_head req_free;
+
+ /*
+ * USB requests video pump thread has already encoded into. These are
+ * ready to be queued to the endpoint.
+ */
+ struct list_head req_ready;
spinlock_t req_lock;
unsigned int req_int_count;
@@ -268,6 +268,100 @@ static int uvcg_video_ep_queue(struct uvc_video *video, struct usb_request *req)
return ret;
}
+/* This function must be called with video->req_lock held. */
+static int uvcg_video_usb_req_queue(struct uvc_video *video,
+ struct usb_request *req, bool queue_to_ep)
+{
+ bool is_bulk = video->max_payload_size;
+ struct list_head *list = NULL;
+
+ if (!video->is_enabled) {
+ uvc_video_free_request(req->context, video->ep);
+ return -ENODEV;
+ }
+ if (queue_to_ep) {
+ struct uvc_request *ureq = req->context;
+ /*
+ * With USB3 handling more requests at a higher speed, we can't
+ * afford to generate an interrupt for every request. Decide to
+ * interrupt:
+ *
+ * - When no more requests are available in the free queue, as
+ * this may be our last chance to refill the endpoint's
+ * request queue.
+ *
+ * - When this is request is the last request for the video
+ * buffer, as we want to start sending the next video buffer
+ * ASAP in case it doesn't get started already in the next
+ * iteration of this loop.
+ *
+ * - Four times over the length of the requests queue (as
+ * indicated by video->uvc_num_requests), as a trade-off
+ * between latency and interrupt load.
+ */
+ if (list_empty(&video->req_free) || ureq->last_buf ||
+ !(video->req_int_count %
+ DIV_ROUND_UP(video->uvc_num_requests, 4))) {
+ video->req_int_count = 0;
+ req->no_interrupt = 0;
+ } else {
+ req->no_interrupt = 1;
+ }
+ video->req_int_count++;
+ return uvcg_video_ep_queue(video, req);
+ }
+ /*
+ * If we're not queuing to the ep, for isoc we're queuing
+ * to the req_ready list, otherwise req_free.
+ */
+ list = is_bulk ? &video->req_free : &video->req_ready;
+ list_add_tail(&req->list, list);
+ return 0;
+}
+
+/*
+ * Must only be called from uvcg_video_enable - since after that we only want to
+ * queue requests to the endpoint from the uvc_video_complete complete handler.
+ * This function is needed in order to 'kick start' the flow of requests from
+ * gadget driver to the usb controller.
+ */
+static void uvc_video_ep_queue_initial_requests(struct uvc_video *video)
+{
+ struct usb_request *req = NULL;
+ unsigned long flags = 0;
+ unsigned int count = 0;
+ int ret = 0;
+ /*
+ * We only queue half of the free list since we still want to have
+ * some free usb_requests in the free list for the video_pump async_wq
+ * thread to encode uvc buffers into. Otherwise we could get into a
+ * situation where the free list does not have any usb requests to
+ * encode into - we always end up queueing 0 length requests to the
+ * end point.
+ */
+ unsigned int half_list_size = video->uvc_num_requests / 2;
+
+ spin_lock_irqsave(&video->req_lock, flags);
+ /*
+ * Take these requests off the free list and queue them all to the
+ * endpoint. Since we queue 0 length requests with the req_lock held,
+ * there isn't any 'data' race involved here with the complete handler.
+ */
+ while (count < half_list_size) {
+ req = list_first_entry(&video->req_free, struct usb_request,
+ list);
+ list_del(&req->list);
+ req->length = 0;
+ ret = uvcg_video_ep_queue(video, req);
+ if (ret < 0) {
+ uvcg_queue_cancel(&video->queue, /*disconnect*/0);
+ break;
+ }
+ count++;
+ }
+ spin_unlock_irqrestore(&video->req_lock, flags);
+}
+
static void
uvc_video_complete(struct usb_ep *ep, struct usb_request *req)
{
@@ -276,6 +370,8 @@ uvc_video_complete(struct usb_ep *ep, struct usb_request *req)
struct uvc_video_queue *queue = &video->queue;
struct uvc_buffer *last_buf = NULL;
unsigned long flags;
+ bool is_bulk = video->max_payload_size;
+ int ret = 0;
spin_lock_irqsave(&video->req_lock, flags);
if (!video->is_enabled) {
@@ -329,8 +425,46 @@ uvc_video_complete(struct usb_ep *ep, struct usb_request *req)
* back to req_free
*/
if (video->is_enabled) {
- list_add_tail(&req->list, &video->req_free);
- queue_work(video->async_wq, &video->pump);
+ /*
+ * Here we check whether any request is available in the ready
+ * list. If it is, queue it to the ep and add the current
+ * usb_request to the req_free list - for video_pump to fill in.
+ * Otherwise, just use the current usb_request to queue a 0
+ * length request to the ep. Since we always add to the req_free
+ * list if we dequeue from the ready list, there will never
+ * be a situation where the req_free list is completely out of
+ * requests and cannot recover.
+ */
+ struct usb_request *to_queue = req;
+
+ to_queue->length = 0;
+ if (!list_empty(&video->req_ready)) {
+ to_queue = list_first_entry(&video->req_ready,
+ struct usb_request, list);
+ list_del(&to_queue->list);
+ /* Add it to the free list. */
+ list_add_tail(&req->list, &video->req_free);
+ /*
+ * Queue work to the wq as well since it is possible that a
+ * buffer may not have been completely encoded with the set of
+ * in-flight usb requests for whih the complete callbacks are
+ * firing.
+ * In that case, if we do not queue work to the worker thread,
+ * the buffer will never be marked as complete - and therefore
+ * not be returned to userpsace. As a result,
+ * dequeue -> queue -> dequeue flow of uvc buffers will not
+ * happen.
+ */
+ queue_work(video->async_wq, &video->pump);
+ }
+ /*
+ * Queue to the endpoint. The actual queueing to ep will
+ * only happen on one thread - the async_wq for bulk endpoints
+ * and this thread for isoc endpoints.
+ */
+ ret = uvcg_video_usb_req_queue(video, to_queue, !is_bulk);
+ if (ret < 0)
+ uvcg_queue_cancel(queue, 0);
} else {
uvc_video_free_request(ureq, ep);
}
@@ -347,6 +481,7 @@ uvc_video_free_requests(struct uvc_video *video)
INIT_LIST_HEAD(&video->ureqs);
INIT_LIST_HEAD(&video->req_free);
+ INIT_LIST_HEAD(&video->req_ready);
video->req_size = 0;
return 0;
}
@@ -424,8 +559,7 @@ static void uvcg_video_pump(struct work_struct *work)
struct usb_request *req = NULL;
struct uvc_buffer *buf;
unsigned long flags;
- bool buf_done;
- int ret;
+ int ret = 0;
while (true) {
if (!video->ep->enabled)
@@ -454,15 +588,6 @@ static void uvcg_video_pump(struct work_struct *work)
if (buf != NULL) {
video->encode(req, video, buf);
- buf_done = buf->state == UVC_BUF_STATE_DONE;
- } else if (!(queue->flags & UVC_QUEUE_DISCONNECTED) && !is_bulk) {
- /*
- * No video buffer available; the queue is still connected and
- * we're transferring over ISOC. Queue a 0 length request to
- * prevent missed ISOC transfers.
- */
- req->length = 0;
- buf_done = false;
} else {
/*
* Either the queue has been disconnected or no video buffer
@@ -473,45 +598,25 @@ static void uvcg_video_pump(struct work_struct *work)
break;
}
- /*
- * With USB3 handling more requests at a higher speed, we can't
- * afford to generate an interrupt for every request. Decide to
- * interrupt:
- *
- * - When no more requests are available in the free queue, as
- * this may be our last chance to refill the endpoint's
- * request queue.
- *
- * - When this is request is the last request for the video
- * buffer, as we want to start sending the next video buffer
- * ASAP in case it doesn't get started already in the next
- * iteration of this loop.
- *
- * - Four times over the length of the requests queue (as
- * indicated by video->uvc_num_requests), as a trade-off
- * between latency and interrupt load.
- */
- if (list_empty(&video->req_free) || buf_done ||
- !(video->req_int_count %
- DIV_ROUND_UP(video->uvc_num_requests, 4))) {
- video->req_int_count = 0;
- req->no_interrupt = 0;
- } else {
- req->no_interrupt = 1;
- }
-
- /* Queue the USB request */
- ret = uvcg_video_ep_queue(video, req);
spin_unlock_irqrestore(&queue->irqlock, flags);
+ spin_lock_irqsave(&video->req_lock, flags);
+ /* For bulk end points we queue from the worker thread
+ * since we would preferably not want to wait on requests
+ * to be ready, in the uvcg_video_complete() handler.
+ * For isoc endpoints we add the request to the ready list
+ * and only queue it to the endpoint from the complete handler.
+ */
+ ret = uvcg_video_usb_req_queue(video, req, is_bulk);
+ spin_unlock_irqrestore(&video->req_lock, flags);
+
if (ret < 0) {
uvcg_queue_cancel(queue, 0);
break;
}
- /* Endpoint now owns the request */
+ /* The request is owned by the endpoint / ready list. */
req = NULL;
- video->req_int_count++;
}
if (!req)
@@ -567,7 +672,7 @@ uvcg_video_disable(struct uvc_video *video)
spin_lock_irqsave(&video->req_lock, flags);
/*
- * Remove all uvc_reqeusts from ureqs with list_del_init
+ * Remove all uvc_requests from ureqs with list_del_init
* This lets uvc_video_free_request correctly identify
* if the uvc_request is attached to a list or not when freeing
* memory.
@@ -580,8 +685,14 @@ uvcg_video_disable(struct uvc_video *video)
uvc_video_free_request(req->context, video->ep);
}
+ list_for_each_entry_safe(req, temp, &video->req_ready, list) {
+ list_del(&req->list);
+ uvc_video_free_request(req->context, video->ep);
+ }
+
INIT_LIST_HEAD(&video->ureqs);
INIT_LIST_HEAD(&video->req_free);
+ INIT_LIST_HEAD(&video->req_ready);
video->req_size = 0;
spin_unlock_irqrestore(&video->req_lock, flags);
@@ -635,7 +746,7 @@ int uvcg_video_enable(struct uvc_video *video)
video->req_int_count = 0;
- queue_work(video->async_wq, &video->pump);
+ uvc_video_ep_queue_initial_requests(video);
return ret;
}
@@ -648,6 +759,7 @@ int uvcg_video_init(struct uvc_video *video, struct uvc_device *uvc)
video->is_enabled = false;
INIT_LIST_HEAD(&video->ureqs);
INIT_LIST_HEAD(&video->req_free);
+ INIT_LIST_HEAD(&video->req_ready);
spin_lock_init(&video->req_lock);
INIT_WORK(&video->pump, uvcg_video_pump);