[Intel-gfx] [PATCH] drm/i915: preserve dispaly init order on ByT

[Daniel Vetter]

On Wed, Oct 16, 2013 at 06:10:41PM +0300, Artem Bityutskiy wrote:
> From: Artem Bityutskiy <artem.bityutskiy at linux.intel.com>
> 
> This patch changes HDMI port registration order for the BayTrail platform.
> 
> The story is that in kernel version 3.11 i915 supported only one HDMI port -
> the HDMIB port. So this port ended up being HDMI-1 in user-space.
> 
> But commit '6f6005a drm/i915: expose HDMI connectors on port C on BYT'
> introduced HDMIC port support. And added HDMIC  registration prior to HDMIB,
> so HDMIB became HDMI-2 and HDMIC became HDMI-1.
> 
> Well, this is fine as far as the kernel is concerned. i915 does not give any
> guarantees to the numbering, and has never given them.
> 
> However, this breaks wayland setup in Tizen IVI. We have only one single HDMI
> port on our hardware, and it is connected to HDMIB. Our configuration relies on
> the fact that it is HDMI-1.
> 
> Well, certainly this is user-space problem which was exposed with Jesse's
> patch. However, there is a reason why we have to do this assumption - we use
> touchscreen monitors and we have to associate event devices with the monitors,
> and this is not easy to do dynamically, so we just have a static setup.
> 
> Anyway, while the user-space setup will have to be fixed regardless, let's
> chane the HDMI port registration order so that HDMIB stays HDMI-1, just like it
> was in 3.11. Simply because there is no strong reason for changing the order in
> the kernel, and it'll help setups like ours in sense that we'll have more time
> for fixing the issue properly.
> 
> Also amend the commentary which looks a bit out-of-date.
> 
> Signed-off-by: Artem Bityutskiy <artem.bityutskiy at linux.intel.com>

This makes imo sense irrespective of any userspace issues. Queued for
-next, thanks for the patch.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch