[Letux-kernel] drm/omap: Remove panel-dpi driver

Laurent Pinchart laurent.pinchart at ideasonboard.com
Thu Apr 18 22:59:29 CEST 2019


Hi Tomi,

On Thu, Apr 11, 2019 at 09:32:26AM +0300, Tomi Valkeinen wrote:
> On 11/04/2019 09:14, H. Nikolaus Schaller wrote:
> 
> >> You will need the panel data to be added to the simple panel driver, as
> >> it won't read the timings from the DT (unfortunately, in my opinion).
> > 
> > Hm. How does this work? Is there a description? I have no experience with
> > DRM simple panel.
> 
> See drivers/gpu/drm/panel/panel-simple.c, it just has a list of
> compatibles, and pointers to the (more or less) same data as is in the
> DT. And see a commit that adds a new panel, e.g. "drm/panel: simple: Add
> OSD070T1718-19TS panel support".
> 
> > So with this DTB stability policy in mind it seems too early to remove the
> > panel-dpi driver unless there is a compatible solution which does not break
> > existing DTB.
> 
> Well, maybe just reverting "drm/omap: Remove panel-dpi driver" would be
> enough. I didn't try, but I think all the plumbing is still there to
> keep the legacy omapdrm panels working.
> 
> If I'm not mistaken, Laurent did try to get the simple-panel to get the
> timings from the DT, but it was rejected. Perhaps backward-compatibility
> with out-of-tree dtbs would be a valid reason to get it accepted?
> Laurent, what do you think?

Sorry for the late reply, this thread got burried in my inbox when I was
travelling last week.

There have been two recent attempts to support reading modes from DT for
panels (see [1] and [2]), so I think there's still hope :-) I agree
there are pros and cons though, it's not an easy decision.

[1] https://lore.kernel.org/lkml/20190408103240.GF6644@ulmo/T/
[2] https://patchwork.kernel.org/patch/10842593/

> That said, in my opinion, we should not care too much about out-of-tree
> stuff. It's a nightmare to support things that you're not even aware of.
> In this particular case, adding the out-of-tree panels to simple-panel
> should be a very straightforward task, and doesn't need a change in the
> dtbs themselves.

-- 
Regards,

Laurent Pinchart


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