[Intel-gfx] [PATCH 1/2] drm/i915: make backlight functions take a connector

[Daniel Vetter]

On Mon, Sep 30, 2013 at 2:15 PM, Ville Syrjälä
<ville.syrjala at linux.intel.com> wrote:
> I was discussing things a bit with Jani, and I'll repeat my thoughts
> here for others to see. Feel free to kick me if I get things totally
> wrong as I don't know the backlight code, nor do I really want to.
>
> We may need to handle backlight configuration requests when there's no
> pipe attached to the port, and we also want to be able to change the
> pipe<->port mapping, so my idea would be to shadow the backlight
> registers in the connector, and when we assign a pipe to the port,
> we write all the regs from the shadow copies to the real pipe blc
> registers. Otherwise I'm worried about all the rmw stuff we do to the
> registers, and leaving bits around in the registers from when the pipe
> was still used with some other port.

I think that's the sanest approach (maybe keep the shadow values
around in a backligh struct or intel_panel). Then we could also drop
our reliance on the save/restore logic in i915_suspend.c, which will
kill the 2nd copy of the fragile backlight register read/write code.
Finally if we initialize the shadow values at module load time we can
also ditch the imo fragile delayed register saving logic we currently
have.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch