Re: [PATCH 0/1] drm/i915: Allow specifying a minimum brightness level for sysfs control.

On Tue, Mar 26, 2013 at 12:48:44PM +0100, Danny Baumann wrote:

This patch makes the behaviour of the intel_backlight backlight device consistent to e.g. acpi_videoX: When writing the value 0, the set brightness makes the panel content barely readable instead of turning the backlight off. This matches the expectations of user space (e.g. kde-workspace or the Intel X11 driver), which expects that it can use intel_backlight as a drop-in replacement for acpi_videoX.

I'm not quite clear what you mean here. The behaviour of "0" isn't well defined for the ACPI backlight driver - it's perfectly reasonable for it to turn the backlight off entirely. Anything assuming that "0" is still visible is broken.