On Fri, 23 Jul 2010 14:00:30 -0400, Andrew Lutomirski <l...@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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