linux-kernel - Re: [PATCH v2 0/4] uvc: Restore old vdev name

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Date:   Tue, 14 Dec 2021 15:44:09 +0100
From:   Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
To:     Ricardo Ribalda <ribalda@...omium.org>
Cc:     Nicolas Dufresne <nicolas@...fresne.ca>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        tfiga@...omium.org
Subject: Re: [PATCH v2 0/4] uvc: Restore old vdev name

Em Tue,  7 Dec 2021 01:38:36 +0100
Ricardo Ribalda <ribalda@...omium.org> escreveu:

> In order to have unique entity names, we decided to change the name of
> the video devices with their functionality.
> 
> This has resulted in some (all?) GUIs showing not useful names.
> 
> This patchset reverts the original patch and introduces a new one to
> allow having different entity and vdev names.
> 
> Since some distros have ported the reverted patch to their stable
> kernels, it would be great if we can get this sent asap, to avoid making
> more people angry ;).

Yeah, patch 1 of this series makes a lot sense. Reporting a camera
as "Video Capture" doesn't seem too nice, specially if multiple
UVC cameras are present.

Yet, I'm a little in doubt about patch 4/4, for a couple of reasons:

1. IMO, on *all* devices (not only uvc), it makes sense to add a "Metadata" 
   at the name string for the metadata devnodes.

   So, I would implement such logic at V4L2 core instead.

2. Such metadata string should be there not only for the entity name,
   but also for vdev->name;

3. I would, instead, set the device name as:

	vdev->name = "Meta: <foo>"

   for the meta devnodes, as the string size is limited.

4. As almost all devices have either video capture or video
   output, I can't see any value to unconditionally add
   "Video Capture"/"Video Output" strings. It would only make
   sense to have them on devices that report having both.

Regards,
Mauro

> 
> v2:
>  - Add Documentation
>  - Mark maybe unused variables as __maybe_unused
>  - Add Suggested-by
> 
> Ricardo Ribalda (4):
>   Revert "media: uvcvideo: Set unique vdev name based in type"
>   media: v4l2-dev.c: Allow driver-defined entity names
>   media: Documentation/driver-api: Document entity name
>   media: uvcvideo: Set unique entity name based in type
> 
>  Documentation/driver-api/media/v4l2-dev.rst |  4 ++++
>  drivers/media/usb/uvc/uvc_driver.c          | 14 +++++++++++---
>  drivers/media/v4l2-core/v4l2-dev.c          |  4 +++-
>  3 files changed, 18 insertions(+), 4 deletions(-

Thanks,
Mauro