[PATCH v2] drm: get fbdev size from cmdline mode if it exists

[Daniel Vetter]

On Tue, Jan 10, 2017 at 10:06:44PM +0200, Laurent Pinchart wrote:
> Hi Vincent,
> 
> On Tuesday 10 Jan 2017 13:33:29 Vincent ABRIOU wrote:
> > On 01/10/2017 12:39 PM, Daniel Vetter wrote:
> > > On Tue, Jan 10, 2017 at 12:21:09PM +0100, Vincent Abriou wrote:
> > >> In case no connector is found while creating the fbdev, gives the
> > >> possibility to specify the default fbdev size by firstly checking if the
> > >> command line is defining a preferred mode. Else go into fallback and set
> > >> 1024x768 fbdev size as it was already done.
> > >> 
> > >> Cc: Tomi Valkeinen <tomi.valkeinen at ti.com>
> > >> Signed-off-by: Vincent Abriou <vincent.abriou at st.com>
> > > 
> > > btw on all this there's also the possible solution to delay setup of the
> > > fbdev until the first connector switches to connected, and then only
> > > allocting the fb and doing the setup. Tegra has that, and Thierry did some
> > > patches to move that logic into the fb helpers. But there's some locking
> > > issues that need to be fixed first, hence why those patches haven't landed
> > > yet.
> > > 
> > > But if you never probe the right mode, this here sounds like a good idea
> > > too.
> > 
> > The early creation of fbdev is useful for userland system. If fbdev
> > creation is delayed until first connector is connected, userland systems
> > startup could fails (like Android that check fbdev availability at startup).
> > 
> > Today if no connector is connected, a default 1024x768 fbdev is created
> > but it does not necessarily match the targeted CRTC size. When the
> > connector is connected, fbdev is not reconfigured with the targeted CRTC
> > size and it is anyway too late for the userland to take into account new
> > fbdev size. Reading the cmdline is an easy way to solve this.
> 
> Isn't it another case of working around userspace issue in the kernel ? 
> Shouldn't the offending userspace code be fixed ? And while at it, moved from 
> fbdev to DRM/KMS ? :-) I wrote a proof-of-concept patch a few years ago to use 
> DRM/KMS in the Android init process. I'm sure it doesn't apply cleanly 
> anymore, but I can share it if you're interested.

So android still doesn't boot without fbdev? I thought that's been fixed
...
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch