linux-kernel - [PATCH v5 7/9] usb: gadget: uvc: set nbuffers to minimum STREAMING_MIN_BUFFERS in uvc_queue

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Message-Id: <20240403-uvc_request_length_by_interval-v5-7-2de78794365c@pengutronix.de>
Date: Fri, 27 Sep 2024 01:37:46 +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>, 
 Avichal Rakesh <arakesh@...gle.com>, 
 Jayant Chowdhary <jchowdhary@...gle.com>
Cc: linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Michael Grzeschik <m.grzeschik@...gutronix.de>
Subject: [PATCH v5 7/9] usb: gadget: uvc: set nbuffers to minimum
 STREAMING_MIN_BUFFERS in uvc_queue_setup

We set the minimum amount of v4l2 buffers that is possibly be pending
to UVCG_STREAMING_MIN_BUFFERS which is two. This way the driver will
always have at least one frame pending to be encoded while the other
is being enqueued in the hardware.

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

---
v4 -> v5:
 - using STREAMING_MIN_BUFFERS set the min nbuffers
 - renamed the patch since the function changed
 - removed the g_ctrl function
 - reordered this patch in the series
v1 -> v4: -
---
 drivers/usb/gadget/function/uvc.h       | 2 ++
 drivers/usb/gadget/function/uvc_queue.c | 3 +++
 2 files changed, 5 insertions(+)

diff --git a/drivers/usb/gadget/function/uvc.h b/drivers/usb/gadget/function/uvc.h
index bedb4ef42864f..6f44dd7323150 100644
--- a/drivers/usb/gadget/function/uvc.h
+++ b/drivers/usb/gadget/function/uvc.h
@@ -74,6 +74,8 @@ extern unsigned int uvc_gadget_trace_param;
 #define UVCG_REQ_MAX_INT_COUNT			16
 #define UVCG_REQ_MAX_ZERO_COUNT			(2 * UVCG_REQ_MAX_INT_COUNT)
 
+#define UVCG_STREAMING_MIN_BUFFERS		2
+
 /* ------------------------------------------------------------------------
  * Structures
  */
diff --git a/drivers/usb/gadget/function/uvc_queue.c b/drivers/usb/gadget/function/uvc_queue.c
index 6757a4e25a743..5eaeae3e2441c 100644
--- a/drivers/usb/gadget/function/uvc_queue.c
+++ b/drivers/usb/gadget/function/uvc_queue.c
@@ -21,6 +21,7 @@
 #include <media/videobuf2-vmalloc.h>
 
 #include "uvc.h"
+#include "uvc_video.h"
 
 /* ------------------------------------------------------------------------
  * Video buffers queue management.
@@ -47,6 +48,8 @@ static int uvc_queue_setup(struct vb2_queue *vq,
 
 	if (*nbuffers > UVC_MAX_VIDEO_BUFFERS)
 		*nbuffers = UVC_MAX_VIDEO_BUFFERS;
+	if (*nbuffers < UVCG_STREAMING_MIN_BUFFERS)
+		*nbuffers = UVCG_STREAMING_MIN_BUFFERS;
 
 	*nplanes = 1;
 

-- 
2.39.5