Commit 5ae8a354 authored by Avichal Rakesh's avatar Avichal Rakesh Committed by Greg Kroah-Hartman
Browse files

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: default avatarAvichal Rakesh <arakesh@google.com>
Reviewed-by: default avatarLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Message-ID: <20230602220455.313801-1-arakesh@google.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 152669f8

drivers/usb/gadget/function/uvc_video.c

+25 −13
Original line number Diff line number Diff line
@@ -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;