usb: gadget: uvc: Utilise instance name in video name

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Kieran,

Thank you for the patch.

On Tuesday, 22 May 2018 18:29:49 EEST Kieran Bingham wrote:
> From: Kieran Bingham <kieran.bingham@ideasonboard.com>
> 
> With multiple UVC gadgets on a composite device, the device names become
> indistinguishable from one another.
> 
> Extend the gadget video name to incorporate the function instance name,
> along side the existing UDC controller name.
> 
> Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> ---
>  drivers/usb/gadget/function/f_uvc.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/gadget/function/f_uvc.c
> b/drivers/usb/gadget/function/f_uvc.c index 1affa8e3a974..65454a31ad68
> 100644
> --- a/drivers/usb/gadget/function/f_uvc.c
> +++ b/drivers/usb/gadget/function/f_uvc.c
> @@ -433,7 +433,9 @@ uvc_register_video(struct uvc_device *uvc)
>  	uvc->vdev.release = video_device_release_empty;
>  	uvc->vdev.vfl_dir = VFL_DIR_TX;
>  	uvc->vdev.lock = &uvc->video.mutex;
> -	strlcpy(uvc->vdev.name, cdev->gadget->name, sizeof(uvc->vdev.name));
> +
> +	snprintf(uvc->vdev.name, sizeof(uvc->vdev.name), "%s:%s",
> +		 cdev->gadget->name, uvc->func.fi->group.cg_item.ci_name);

If the function is instantiated from the legacy g_webcam, the whole group 
structure will be zero, so ci_name will be empty. I think you should omit the 
":" in that case.

I also wonder whether the vdev.name field will always be long enough. If we 
can't guarantee that, would it make sense to instead expose the config item 
name through a custom sysfs property for the video device ?

>  	video_set_drvdata(&uvc->vdev, uvc);