Re: [PATCH] drm, drm/i915/lvds: Honour video= parameter to override LVDS fixed mode

Mike Isely
2011-03-29T07:21:19Z

On Mon, 28 Mar 2011, Keith Packard wrote:

> On Tue, 29 Mar 2011 07:49:12 +0100, Chris Wilson <chris@chris-wilson.co.uk> wrote:
>
> > Yes, Oliver pointed out that we need to pass much more panel
> > configuration data in order to configure a bare LVDS. Given the bizarre
> > situation of the LVDS-attached-HDMI PNV boxes (how I love our market
> > differentiate strategy!), I think we have to accept the user-override.
>
> Seems like PNV needs a simpler override (don't use LVDS scaler at all,
> just set native modes directly). Any chance we could auto-detect this
> via the LVDS DDC link?

I posted a patch on this list 12 days ago that in fact implements
"disable-the-scaler" capability. It's the same fix I did almost exactly
3 years ago for the userspace Intel xorg driver - it implemented
"lvdsfixedmode" as an xorg driver option. The patch comments in that
post reference the older UMS fixes, still documented in a bugzilla entry
from back then.

There were two related patches posted as well, one allows user control
of 18 vs 24 bit LVDS, and the other allows control of single vs dual
channel mode.

I ended up doing all of this due to a project using a special purpose 24
bit display that is connected via "bare" LVDS to an SBC whose BIOS
otherwise has zero knowledge of that display device... This project has
gone on for, well, 3 years which is the reason why I did those patches 3
years ago. I had to revisit it again now because of an upgrade that
forced us over to KMS, whereupon I soon found the same LVDS problems
there as what had been previously fixed in the userspace driver.

The issue as I understand it is not so much whether these patches should
be merged but rather that each results in another kernel module option
and it'd sure be nice to have a unified simple way to control these new
flags, like perhaps an extension to "video=".

-Mike

--

Mike Isely
isely @ isely (dot) net
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