linux-kernel - Re: [PATCH v4 3/3] media: uvcvideo: Add a unique suffix to camera names

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Message-ID: <Y45tnp0naosOrYCY@pendragon.ideasonboard.com>
Date:   Tue, 6 Dec 2022 00:15:58 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Ricardo Ribalda <ribalda@...omium.org>
Cc:     Yunke Cao <yunkec@...omium.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        linux-media@...r.kernel.org,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 3/3] media: uvcvideo: Add a unique suffix to camera
 names

Hi Ricardo,

Thank you for the patch.

On Fri, Dec 02, 2022 at 06:08:19PM +0100, Ricardo Ribalda wrote:
> Some cameras have multiple data inputs (i.e. IR sensor and RGB sensor),
> append a unique number to the device name.
> 
> Fixes v4l2-compliance:
>     Media Controller ioctls:
>          fail: v4l2-test-media.cpp(205): v2_entity_names_set.find(key) != v2_entity_names_set.end()
>        test MEDIA_IOC_G_TOPOLOGY: FAIL
>          fail: v4l2-test-media.cpp(394): num_data_links != num_links
>        test MEDIA_IOC_ENUM_ENTITIES/LINKS: FAIL
> 
> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> ---
>  drivers/media/usb/uvc/uvc_driver.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> index 215fb483efb0..f4032ebb3689 100644
> --- a/drivers/media/usb/uvc/uvc_driver.c
> +++ b/drivers/media/usb/uvc/uvc_driver.c
> @@ -1963,7 +1963,8 @@ int uvc_register_video_device(struct uvc_device *dev,
>  		break;
>  	}
>  
> -	strscpy(vdev->name, dev->name, sizeof(vdev->name));
> +	snprintf(vdev->name, sizeof(vdev->name), "%s %u", dev->name,
> +		 stream->header.bTerminalLink);

This won't be perfect as the string is not guaranteed to fit in
vdev->name, but I suppose it will help as a quick fix for some devices.
How about the other devices ? Won't they still exhibit the above
v4l2-compliance failure ? Isn't that something that will still affect
Chrome OS devices ?

The change should not cause any regression as big as in patch 1/3.
However, unless I'm mistaken users will notice a device name change,
especially when selecting a device in their web browser. Could that be a
problem ?

>  	/*
>  	 * Set the driver data before calling video_register_device, otherwise
> 

-- 
Regards,

Laurent Pinchart