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usb: gadget: uvc: clean up comments and styling in video_pump 

This patch elaborates on some of the edge cases handled by
video_pump around setting no_interrupt flag, and brings the
code style in line with rest of the file.

Link: https://lore.kernel.org/20230602151916.GH26944@pendragon.ideasonboard.com/
Signed-off-by: Avichal Rakesh <arakesh@google.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Message-ID: <20230602220455.313801-1-arakesh@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Avichal Rakesh 2023-06-02 15:04:55 -07:00 committed by Greg Kroah-Hartman
parent 152669f844
commit 5ae8a35459
1 changed files with 25 additions and 13 deletions
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38
drivers/usb/gadget/function/uvc_video.c
View File

@ -382,13 +382,13 @@ static void uvcg_video_pump(struct work_struct *work)
{
struct uvc_video *video = container_of(work, struct uvc_video, pump);
struct uvc_video_queue *queue = &video->queue;
/* video->max_payload_size is only set when using bulk transfer */
bool is_bulk = video->max_payload_size;
struct usb_request *req = NULL;
struct uvc_buffer *buf;
unsigned long flags;
bool buf_done;
int ret;
bool buf_int;
/* video->max_payload_size is only set when using bulk transfer */
bool is_bulk = video->max_payload_size;
while (video->ep->enabled) {
/*
@ -414,20 +414,19 @@ static void uvcg_video_pump(struct work_struct *work)
if (buf != NULL) {
video->encode(req, video, buf);
/* Always interrupt for the last request of a video buffer */
buf_int = buf->state == UVC_BUF_STATE_DONE;
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 traferring over ISOC. Queue a 0 length request to
* we're transferring over ISOC. Queue a 0 length request to
* prevent missed ISOC transfers.
*/
req->length = 0;
buf_int = false;
buf_done = false;
} else {
/*
* Either queue has been disconnected or no video buffer
* available to bulk transfer. Either way, stop processing
* Either the queue has been disconnected or no video buffer
* available for bulk transfer. Either way, stop processing
* further.
*/
spin_unlock_irqrestore(&queue->irqlock, flags);
@ -435,11 +434,24 @@ static void uvcg_video_pump(struct work_struct *work)
}
/*
* With usb3 we have more requests. This will decrease the
* interrupt load to a quarter but also catches the corner
* cases, which needs to be handled.
* 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_int ||
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;