Mailinglist Archive: radeonhd (265 mails)

[Matthias Hopf <mhopf@xxxxxxx>]

On Jan 07, 09 11:33:57 -0800, Yang Zhao wrote:
> 2009/1/7 Matthias Hopf <mhopf@xxxxxxx>:
> > AFAICS, RandR's gamma hook only deals with 256-Entry tables - could
> > *that* be an issue?
> The 256-entry limit seems perfectly reasonable to me: that's what
> checking RRGetCrtcGammaSize() is for.

Ok, was just a wild guess.

> The issue is that RRSetCrtcGammaRamp() is connected directly to
> LUTxSet(), which doesn't do any data sanitization of its own, and
> simply write to the registers. This is fine for XF86VidMode* where
> truncation is done before reaching DDX code, but fails via RandR when
> 16-bit values that are assumed to be shorter end up being shifted and
> ORed together. Simple matter of doing some shifting as CARD16* ramps
> are packed into LOCO*.

So the same API function is used with different semantics. Which can
never work. How come that this is not hitting other drivers and/or users
- or is it hitting them, and they are just in a minority, thus
overlooked by the X community?

> > Good luck. As I said I have zero to no knowledge about this, and Luc
> > told me yesterday that this is approximately the only place in X where
> > he's actually scared of ;-)
>
> Encouraging. ;)
> Well, I gotta scratch this itch one way or another.

Please continue to tell us your findings. It's really interesting,
especially as almost nobody understands this subsystem well enough.

Matthias

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