[Intel-gfx] [PATCH] drm/i915: expose a fixed brightness range to userspace

[Jesse Barnes]

On Tue, 11 Nov 2014 12:30:38 -0800
"U. Artie Eoff" <ullysses.a.eoff at intel.com> wrote:

> A userspace brightness range that is larger than the hardware
> brightness range does not have a 1:1 mapping and can result
> in brightness != actual_brightness for some values.
> 
> Expose a fixed brightness range of [0..1000] to userspace so
> that all values can map 1:1 into the hardware brightness
> range.  This would assume that the hardware range is always
> greater than 1000, otherwise we're right back to the original
> issue.
> 
> This patch is based on Jani Nikula's proposed change in the
> referenced ML thread, except use the range [0..1000] instead;
> which was recommended by Jesse Barnes for smoother backlight
> transitions.
> 
> Reference: http://lists.freedesktop.org/archives/intel-gfx/2014-November/055221.html
> Signed-off-by: U. Artie Eoff <ullysses.a.eoff at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_panel.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> index 4d63839..f74f5f2 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -1057,7 +1057,7 @@ static int intel_backlight_device_register(struct intel_connector *connector)
>  	 * Note: Everything should work even if the backlight device max
>  	 * presented to the userspace is arbitrarily chosen.
>  	 */
> -	props.max_brightness = panel->backlight.max;
> +	props.max_brightness = 1000;
>  	props.brightness = scale_hw_to_user(connector,
>  					    panel->backlight.level,
>  					    props.max_brightness);

Yeah looks ok to me.  I guess Jani has to ack it too.

Reviewed-by: Jesse Barnes <jbarnes at virtuousgeek.org>

-- 
Jesse Barnes, Intel Open Source Technology Center