linux-kernel - Re: [PATCHv1] video: omapfb2: Make standard and custom DSI command mode panel driver mutually exclusive

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Date:   Tue, 12 Jan 2021 13:02:46 +0100
From:   Sebastian Reichel <sebastian.reichel@...labora.com>
To:     Sam Ravnborg <sam@...nborg.org>
Cc:     Tomi Valkeinen <tomba@...nel.org>,
        Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-next@...r.kernel.org,
        kernel@...labora.com
Subject: Re: [PATCHv1] video: omapfb2: Make standard and custom DSI command
 mode panel driver mutually exclusive

[replace Tomi's TI mail address with something working]

Hi,

On Fri, Jan 08, 2021 at 08:58:39PM +0100, Sam Ravnborg wrote:
> Hi Sebastian,
> 
> On Fri, Jan 08, 2021 at 12:24:41PM +0100, Sebastian Reichel wrote:
> > Standard DRM panel driver for DSI command mode panel used by omapfb2 is also
> > available now. Just like the other panels its module name clashes with the
> > module from drivers/video/fbdev/omap2/omapfb/displays, part of the deprecated
> > omapfb2 fbdev driver. As omapfb2 can only be compiled when the omapdrm driver
> > is disabled, and the DRM panel drivers are useless in that case, make the
> > omapfb2 panel depend on the standard DRM panels being disabled to fix
> > the name clash.
> > 
> > Fixes: cf64148abcfd ("drm/panel: Move OMAP's DSI command mode panel driver")
> > Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
> > Signed-off-by: Sebastian Reichel <sebastian.reichel@...labora.com>
> 
> For a backport this looks good:
> Acked-by: Sam Ravnborg <sam@...nborg.org>

Thanks.

> But why is it it we need omapfb at all when we have omapdrm?

I think there are two reasons omapfb has not been killed yet. One
reason was missing support for manually updated DSI panels, which
have been working since 1 or 2 kernel releases now. The other reason
is some people using it in combination with an out-of-tree PowerVR
kernel driver. There is currently work going on to use a more recent
PowerVR driver based on omapdrm driven by Maemo Leste people.

> Can we sunset all or some parts of omap support in video/?
> If not, what is missing to do so.

IDK the exact status of the PowerVR work and have not been using
omapfb myself for years. I don't think there is a reason to rush
this, so my suggestion is removing it in 3 steps giving people
the chance to complain:

1. Add 'depends on EXPERT' to 'FB_OMAP2' and add deprecation notice
   referencing omapdrm in help text in 5.12
2. Add 'depends on BROKEN' in 5.13
3. Drop drivers/video/fbdev/omap2 afterwards

-- Sebastian

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