linux-kernel - Re: [REGRESSION] Re: [PATCH v10 11/21] media: uvcvideo: Set unique vdev name based in type

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Message-ID: <Ya5hZtwcfBU/19CU@pendragon.ideasonboard.com>
Date:   Mon, 6 Dec 2021 21:15:50 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Nicolas Dufresne <nicolas@...fresne.ca>
Cc:     Ricardo Ribalda <ribalda@...omium.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        tfiga@...omium.org, stable <stable@...r.kernel.org>
Subject: Re: [REGRESSION] Re: [PATCH v10 11/21] media: uvcvideo: Set unique
 vdev name based in type

Hi Nicolas,

On Mon, Dec 06, 2021 at 02:05:06PM -0500, Nicolas Dufresne wrote:
> Le vendredi 18 juin 2021 à 14:29 +0200, Ricardo Ribalda a écrit :
> > All the entities must have a unique name. We can have a descriptive and
> > unique name by appending the function and the entity->id.
> 
> Thanks for your work. The only issue is that unfortunately this change cause an
> important regression for users. All UVC cameras in all UIs seems to no longer
> include any information about the camera. As an example, I have two cameras on
> my system and Firefox, Chrome, Cheese, Zoom and MS Team all agree that my camera
> are now:
> 
>   Video Capture 4
>   Video Capture 5
> 
> Previously they would be shown as something like:
> 
>   StreamCam
>   Integrated
> 
> We should probably revert this change quickly before it get deployed more
> widely, I have notice the backport being sent for 5.4, 5.10 and 5.14. I'm using
> 5.15 shipped by Fedora team.

Ack.

> As a proper solution, maybe I could suggest to keep using dev->name, but trim it
> enough to fit the " N" string to guaranty that you have enough space in this
> limited 32 char string and use that instead ? This should fit the uniqueness
> requirement without the sacrifice of the only possibly useful information we had
> in that limited string.

That would polute the device name a bit, which isn't very nice for
users. I wonder if we could instead decouple the entity name from the
video device name.

> > This is even resilent to multi chain devices.
> > 
> > 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>
> > Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> > Reviewed-by: Hans Verkuil <hverkuil-cisco@...all.nl>
> > ---
> >  drivers/media/usb/uvc/uvc_driver.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> > index 14b60792ffab..037bf80d1100 100644
> > --- a/drivers/media/usb/uvc/uvc_driver.c
> > +++ b/drivers/media/usb/uvc/uvc_driver.c
> > @@ -2194,6 +2194,7 @@ int uvc_register_video_device(struct uvc_device *dev,
> >  			      const struct v4l2_file_operations *fops,
> >  			      const struct v4l2_ioctl_ops *ioctl_ops)
> >  {
> > +	const char *name;
> >  	int ret;
> >  
> >  	/* Initialize the video buffers queue. */
> > @@ -2222,16 +2223,20 @@ int uvc_register_video_device(struct uvc_device *dev,
> >  	case V4L2_BUF_TYPE_VIDEO_CAPTURE:
> >  	default:
> >  		vdev->device_caps = V4L2_CAP_VIDEO_CAPTURE | V4L2_CAP_STREAMING;
> > +		name = "Video Capture";
> >  		break;
> >  	case V4L2_BUF_TYPE_VIDEO_OUTPUT:
> >  		vdev->device_caps = V4L2_CAP_VIDEO_OUTPUT | V4L2_CAP_STREAMING;
> > +		name = "Video Output";
> >  		break;
> >  	case V4L2_BUF_TYPE_META_CAPTURE:
> >  		vdev->device_caps = V4L2_CAP_META_CAPTURE | V4L2_CAP_STREAMING;
> > +		name = "Metadata";
> >  		break;
> >  	}
> >  
> > -	strscpy(vdev->name, dev->name, sizeof(vdev->name));
> > +	snprintf(vdev->name, sizeof(vdev->name), "%s %u", name,
> > +		 stream->header.bTerminalLink);
> >  
> >  	/*
> >  	 * Set the driver data before calling video_register_device, otherwise

-- 
Regards,

Laurent Pinchart