Re: [PATCH v3 6/6] usb: gadget: uvc: add configfs option for sg support

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Hi Dan

On 17/10/2022 21:54, Dan Vacura wrote:
The scatter gather support doesn't appear to work well with some UDC hw.
Add the ability to turn on the feature depending on the controller in
use.

Signed-off-by: Dan Vacura <w36195@xxxxxxxxxxxx>


Nitpick: I would call it use_sg everywhere, but either way:


Reviewed-by: Daniel Scally <dan.scally@xxxxxxxxxxxxxxxx>

Tested-by: Daniel Scally <dan.scally@xxxxxxxxxxxxxxxx>

---
V1 -> V2:
- no change, new patch in serie
V2 -> V3:
- default on, same as baseline

  Documentation/ABI/testing/configfs-usb-gadget-uvc | 1 +
  Documentation/usb/gadget-testing.rst              | 2 ++
  drivers/usb/gadget/function/f_uvc.c               | 2 ++
  drivers/usb/gadget/function/u_uvc.h               | 1 +
  drivers/usb/gadget/function/uvc_configfs.c        | 2 ++
  drivers/usb/gadget/function/uvc_queue.c           | 4 ++--
  6 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/Documentation/ABI/testing/configfs-usb-gadget-uvc b/Documentation/ABI/testing/configfs-usb-gadget-uvc
index 5dfaa3f7f6a4..839a75fc28ee 100644
--- a/Documentation/ABI/testing/configfs-usb-gadget-uvc
+++ b/Documentation/ABI/testing/configfs-usb-gadget-uvc
@@ -9,6 +9,7 @@ Description:	UVC function directory
  		streaming_interval	1..16
  		function_name		string [32]
  		req_int_skip_div	unsigned int
+		sg_supported		0..1
  		===================	=============================
What: /config/usb-gadget/gadget/functions/uvc.name/control
diff --git a/Documentation/usb/gadget-testing.rst b/Documentation/usb/gadget-testing.rst
index f9b5a09be1f4..8e3072d6a590 100644
--- a/Documentation/usb/gadget-testing.rst
+++ b/Documentation/usb/gadget-testing.rst
@@ -796,6 +796,8 @@ The uvc function provides these attributes in its function directory:
  	function_name       name of the interface
  	req_int_skip_div    divisor of total requests to aid in calculating
  			    interrupt frequency, 0 indicates all interrupt
+	sg_supported        allow for scatter gather to be used if the UDC
+			    hw supports it
  	=================== ================================================
There are also "control" and "streaming" subdirectories, each of which contain
diff --git a/drivers/usb/gadget/function/f_uvc.c b/drivers/usb/gadget/function/f_uvc.c
index e40ca26b9c55..d08ebe3ffeb2 100644
--- a/drivers/usb/gadget/function/f_uvc.c
+++ b/drivers/usb/gadget/function/f_uvc.c
@@ -656,6 +656,7 @@ uvc_function_bind(struct usb_configuration *c, struct usb_function *f)
  			    (opts->streaming_maxburst + 1));
uvc->config_skip_int_div = opts->req_int_skip_div;
+	uvc->video.queue.use_sg = opts->sg_supported;
/* Allocate endpoints. */
  	ep = usb_ep_autoconfig(cdev->gadget, &uvc_control_ep);
@@ -875,6 +876,7 @@ static struct usb_function_instance *uvc_alloc_inst(void)
  	opts->streaming_interval = 1;
  	opts->streaming_maxpacket = 1024;
  	opts->req_int_skip_div = 4;
+	opts->sg_supported = 1;
  	snprintf(opts->function_name, sizeof(opts->function_name), "UVC Camera");
ret = uvcg_attach_configfs(opts);
diff --git a/drivers/usb/gadget/function/u_uvc.h b/drivers/usb/gadget/function/u_uvc.h
index 6f73bd5638ed..5ccced629925 100644
--- a/drivers/usb/gadget/function/u_uvc.h
+++ b/drivers/usb/gadget/function/u_uvc.h
@@ -25,6 +25,7 @@ struct f_uvc_opts {
  	unsigned int					streaming_maxpacket;
  	unsigned int					streaming_maxburst;
  	unsigned int					req_int_skip_div;
+	unsigned int					sg_supported;
unsigned int control_interface;
  	unsigned int					streaming_interface;
diff --git a/drivers/usb/gadget/function/uvc_configfs.c b/drivers/usb/gadget/function/uvc_configfs.c
index 419e926ab57e..3784c0e02d01 100644
--- a/drivers/usb/gadget/function/uvc_configfs.c
+++ b/drivers/usb/gadget/function/uvc_configfs.c
@@ -2351,6 +2351,7 @@ UVCG_OPTS_ATTR(streaming_interval, streaming_interval, 16);
  UVCG_OPTS_ATTR(streaming_maxpacket, streaming_maxpacket, 3072);
  UVCG_OPTS_ATTR(streaming_maxburst, streaming_maxburst, 15);
  UVCG_OPTS_ATTR(req_int_skip_div, req_int_skip_div, UINT_MAX);
+UVCG_OPTS_ATTR(sg_supported, sg_supported, 1);
#undef UVCG_OPTS_ATTR @@ -2401,6 +2402,7 @@ static struct configfs_attribute *uvc_attrs[] = {
  	&f_uvc_opts_attr_streaming_maxpacket,
  	&f_uvc_opts_attr_streaming_maxburst,
  	&f_uvc_opts_attr_req_int_skip_div,
+	&f_uvc_opts_attr_sg_supported,
  	&f_uvc_opts_string_attr_function_name,
  	NULL,
  };
diff --git a/drivers/usb/gadget/function/uvc_queue.c b/drivers/usb/gadget/function/uvc_queue.c
index 02559906a55a..3c7aa5c4bba2 100644
--- a/drivers/usb/gadget/function/uvc_queue.c
+++ b/drivers/usb/gadget/function/uvc_queue.c
@@ -149,11 +149,11 @@ int uvcg_queue_init(struct uvc_video_queue *queue, struct device *dev, enum v4l2
  	queue->queue.buf_struct_size = sizeof(struct uvc_buffer);
  	queue->queue.ops = &uvc_queue_qops;
  	queue->queue.lock = lock;
-	if (cdev->gadget->sg_supported) {
+	if (queue->use_sg && cdev->gadget->sg_supported) {
  		queue->queue.mem_ops = &vb2_dma_sg_memops;
-		queue->use_sg = 1;
  	} else {
  		queue->queue.mem_ops = &vb2_vmalloc_memops;
+		queue->use_sg = false;
  	}
queue->queue.timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_COPY



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