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

[Dan Scally]

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