From: Eric Anholt <eric@anholt.net>
To: Andrew Lutomirski <luto@mit.edu>, intel-gfx@lists.freedesktop.org
Subject: Re: rfc: breaking old userspace gamma for 10-bit support
Date: Fri, 23 Jul 2010 13:13:48 -0700 [thread overview]
Message-ID: <87pqyeklc3.fsf@pollan.anholt.net> (raw)
In-Reply-To: <AANLkTi=skwT=D5Pwz7c2-j+fETjUadNYKjSogqQSct=0@mail.gmail.com>
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On Fri, 23 Jul 2010 14:00:30 -0400, Andrew Lutomirski <luto@mit.edu> wrote:
> AFAICT intel hardware wants a 129-entry LUT when using high precision
> gamma ramps. Rather than hacking some kind of decimation into the
> kernel driver (and thus silently breaking DirectColor), I'd like to
> teach userspace how to deal with variable gamma sizes.
>
> gnome-color-manager already more-or-less supports arbitrary gamma ramp
> sizes (supposedly), dispwin ought to do it, and there might not be any
> other software that really cares. gnome-screensaver saves and
> restores the gamma ramp, and I haven't checked if it works right for
> funny sizes.
>
> The worst problem we'll have is that current xf86-drv-intel can't
> handle non-256 gamma sizes at all. So if we change the kernel we'll
> break it completely.
>
> One option is to have the kernel report gamma_size = 129 but still
> accept 256 and decimate itself. That might cause current userspace to
> keep working (except for DirectColor).
>
> Any thoughts?
The kernel doesn't get to break old userspace. The kernel could support
new userspace that only asks for 129 slots and set a mode that has
better precision in that case. New interfaces would probably be
required to communicate that up front -- I haven't looked into it, but I
just want to make sure you don't spend a bunch of time going down a path
that will be rejected.
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next prev parent reply other threads:[~2010-07-23 20:13 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-23 18:00 rfc: breaking old userspace gamma for 10-bit support Andrew Lutomirski
2010-07-23 20:13 ` Eric Anholt [this message]
2010-07-23 20:29 ` Andrew Lutomirski
2010-07-26 17:26 ` Eric Anholt
2010-07-27 15:03 ` Adam Jackson
2011-04-20 19:05 ` Jesse Barnes
2011-04-20 19:14 ` Andrew Lutomirski
2011-04-20 19:38 ` Jesse Barnes
2011-04-20 19:45 ` Andrew Lutomirski
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