On Fri, Feb 28, 2014 at 04:23:27PM +0000, Russell King - ARM Linux wrote:

On Fri, Feb 28, 2014 at 06:12:23PM +0200, Tomi Valkeinen wrote:

quoted

On 28/02/14 17:59, Russell King - ARM Linux wrote:

quoted

quoted

+dvi0: connector@0 {
+	compatible = "dvi-connector";
+	label = "dvi";
+
+	i2c-bus = <&i2c3>;
+
+	dvi_connector_in: endpoint {
+		remote-endpoint = <&tfp410_out>;
+	};
+};

This looks far too simplistic.  There are different classes of DVI
connector - there is:

DVI A - analogue only
DVI D - digital only (single and dual link)
DVI I - both (single and dual digital link)

DRM at least makes a distinction between these three classes, and this
disctinction is part of the user API.  How would a display system know
which kind of DVI connector is wired up on the board from this DT
description?

Yes, I think that's a valid change. But do we also need to specify
single/dual link, in addition to the three types?

I would argue that as it's a difference in physical hardware, then it
should be described in DT, even if we don't use it.  The reasoning is
that although we may not use it today, we may need to use it in the
future, and as we're describing what the hardware actually is - and
even in this case what pins may be present or missing on the connector,
it's unlikely to be problematical (the only problem is when someone
omits it...)

If you plug a dual-link dvi screen into a soc which can do dual-link but
the actual connector is cheap and doesn't have this wired up
(differentiate wtf) then the kernel needs to know. Otherwise it can't
correctly filter out the modes with dotclocks high enough to require dual
link and the user will look at a black screen.

3.14 has a regression in drm/i915 where we've screwed this up ;-)
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch