linux-kernel - [PATCH 1/3] usb: gadget: function: uvc: set req_size once when the vb2 queue is calculated

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Message-Id: <20240403-uvc_request_length_by_interval-v1-1-9436c4716233@pengutronix.de>
Date: Tue, 09 Apr 2024 23:24:57 +0200
From: Michael Grzeschik <m.grzeschik@...gutronix.de>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
 Daniel Scally <dan.scally@...asonboard.com>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Michael Grzeschik <m.grzeschik@...gutronix.de>
Subject: [PATCH 1/3] usb: gadget: function: uvc: set req_size once when the
 vb2 queue is calculated

The uvc gadget driver is calculating the req_size on every
video_enable/alloc_request and is based on the fixed configfs parameters
maxpacket, maxburst and mult.

As those parameters can not be changed once the gadget is started and
the same calculation is done already early on the
vb2_streamon/queue_setup path its save to remove one extra calculation
and reuse the calculation from uvc_queue_setup for the allocation step.

Signed-off-by: Michael Grzeschik <m.grzeschik@...gutronix.de>

---
Link to v1: https://lore.kernel.org/r/20240404-uvc_request_calc_once-v1-1-fea7fd8f0496@pengutronix.de
---
 drivers/usb/gadget/function/uvc_queue.c |  2 ++
 drivers/usb/gadget/function/uvc_video.c | 15 ++-------------
 2 files changed, 4 insertions(+), 13 deletions(-)

diff --git a/drivers/usb/gadget/function/uvc_queue.c b/drivers/usb/gadget/function/uvc_queue.c
index 0aa3d7e1f3cc3..ce51643fc4639 100644
--- a/drivers/usb/gadget/function/uvc_queue.c
+++ b/drivers/usb/gadget/function/uvc_queue.c
@@ -63,6 +63,8 @@ static int uvc_queue_setup(struct vb2_queue *vq,
 	 */
 	nreq = DIV_ROUND_UP(DIV_ROUND_UP(sizes[0], 2), req_size);
 	nreq = clamp(nreq, 4U, 64U);
+
+	video->req_size = req_size;
 	video->uvc_num_requests = nreq;
 
 	return 0;
diff --git a/drivers/usb/gadget/function/uvc_video.c b/drivers/usb/gadget/function/uvc_video.c
index d41f5f31dadd5..95bb64e16f3da 100644
--- a/drivers/usb/gadget/function/uvc_video.c
+++ b/drivers/usb/gadget/function/uvc_video.c
@@ -496,7 +496,6 @@ 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;
 }
 
@@ -504,16 +503,9 @@ static int
 uvc_video_alloc_requests(struct uvc_video *video)
 {
 	struct uvc_request *ureq;
-	unsigned int req_size;
 	unsigned int i;
 	int ret = -ENOMEM;
 
-	BUG_ON(video->req_size);
-
-	req_size = video->ep->maxpacket
-		 * max_t(unsigned int, video->ep->maxburst, 1)
-		 * (video->ep->mult);
-
 	for (i = 0; i < video->uvc_num_requests; i++) {
 		ureq = kzalloc(sizeof(struct uvc_request), GFP_KERNEL);
 		if (ureq == NULL)
@@ -523,7 +515,7 @@ uvc_video_alloc_requests(struct uvc_video *video)
 
 		list_add_tail(&ureq->list, &video->ureqs);
 
-		ureq->req_buffer = kmalloc(req_size, GFP_KERNEL);
+		ureq->req_buffer = kmalloc(video->req_size, GFP_KERNEL);
 		if (ureq->req_buffer == NULL)
 			goto error;
 
@@ -541,12 +533,10 @@ uvc_video_alloc_requests(struct uvc_video *video)
 		list_add_tail(&ureq->req->list, &video->req_free);
 		/* req_size/PAGE_SIZE + 1 for overruns and + 1 for header */
 		sg_alloc_table(&ureq->sgt,
-			       DIV_ROUND_UP(req_size - UVCG_REQUEST_HEADER_LEN,
+			       DIV_ROUND_UP(video->req_size - UVCG_REQUEST_HEADER_LEN,
 					    PAGE_SIZE) + 2, GFP_KERNEL);
 	}
 
-	video->req_size = req_size;
-
 	return 0;
 
 error:
@@ -699,7 +689,6 @@ uvcg_video_disable(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;
 	spin_unlock_irqrestore(&video->req_lock, flags);
 
 	/*

-- 
2.39.2