[Intel-gfx] BACKLIGHT property for KMS case

[Matthew Garrett]

On Mon, Aug 17, 2009 at 04:57:43PM -0700, Jesse Barnes wrote:

> +static int intel_get_backlight_brightness(struct backlight_device *bd)
> +{
> +	return bd->props.brightness;
> +}

This is what's called when the user reads actual_brightness, so should 
actually read the hardware rather than just returning the cached value.

> +	/* FIXME: check whether /sys/class/backlight is populated or not */

Calling acpi_video_backlight_support() will give you this for acpi. It's 
more complicated for the platform driver case, since that'll typically 
be loaded after us. We're going to need some sort of event generated and 
then unregister the drm backlight in response.

> +	backlight_device->props.max_brightness =
> +		dev_priv->blc_info.inverter_polarity ? 0 : 255;

max_brightness is the maximum value that can be given to the interface, 
rather than the value at which the brightness is greatest. The polarity 
inversion stuff needs to be handled in the set function. I guess there's 
also an argument over what we do about the minimum being greater than 0 
- we should probably scale to cope with that, otherwise UI is going to 
look weird.

-- 
Matthew Garrett | mjg59 at srcf.ucam.org