[PATCHv2 26/31] drm/omap: Create fbdev emulation only for the first DRM connector

[Daniel Vetter]

On Mon, Mar 27, 2017 at 09:28:07AM +0300, Tomi Valkeinen wrote:
> On 25/03/17 23:22, Daniel Vetter wrote:
> > On Fri, Mar 24, 2017 at 11:40:47AM +0200, Tomi Valkeinen wrote:
> >> From: Peter Ujfalusi <peter.ujfalusi at ti.com>
> >>
> >> Add fbdev emulation only for the first DRM connector.
> >> When the fbdev emulation was created for all connectors with different
> >> resolution, the lower res display would only be able to show part of the
> >> framebuffer.
> >> By creating the fbdev emulation only for the first connector we can avoid
> >> this.
> >>
> >> Signed-off-by: Peter Ujfalusi <peter.ujfalusi at ti.com>
> >> Signed-off-by: Tomi Valkeinen <tomi.valkeinen at ti.com>
> > 
> > Why this driver-specific behavior? This is how it works everywhere.
> > 
> > If this doesn't work in some case, then we need to fix this in the fbdev
> > helper. Or have a modparam for that. But definitely not diverging
> > behaviour between drivers.
> 
> The default behavior often results in a rather unusable fbdev on the
> other screen.
> 
> For example, a board with a low-res LCD and HDMI. Fbdev is created based
> in the LCD resolution, and on HDMI you'll get 1080p resolution with a
> tiny fbdev. Or, if fbdev is created based on the HDMI resolution, on the
> LCD you'll see a tiny portion of the huge fbdev.
> 
> I personally did suggest our folks to just disable the fbdev totally,
> but apparently there are still some uses for the fbdev, so this patch
> seemed like a simple way to make the behavior a bit nicer.
> 
> But I agree that it would be best to have this fully configurable, as
> different use cases have different needs. Then again, I'd rather just
> disable the fbdev than start spending time on improving it =).

Yeah I think a module option for  the fbdev helper which implements
exactly this would be fine. Assuming that would make your users happy.

I just want to avoid everyone having to hand-roll the same hacks, since
this problem is the same everywhere (never boot with a retina screen and
the low-res projector plugged in ...).
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch