On Tue, Mar 26, 2013 at 06:10:30PM +0100, Danny Baumann wrote: > Am 26.03.2013 18:02, schrieb Matthew Garrett: > >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. > > Well, the ACPI spec says this (section B.5.2): > > " > The OEM may define the number 0 as "Zero brightness" that can mean > to turn off the lighting (e.g. LCD panel backlight) in the device. > This may be useful in the case of an output device that can still be > viewed using only ambient light, for example, a transflective LCD. > " > > My interpretation of this is that the value 0 is supposed to still > be visible. I'm pretty sure I saw a statement that 0 is supposed to > mean "barely visible" somewhere, but can't find it at the moment. > I'll search for the source of it. I think that's a stretch - "This may be useful" isn't normative language, "The OEM may define" is. But even if we do assert it for the ACPI backlight, it's not true for other interfaces - zero backlight intensity is supposed to be screen off on Apple hardware, for instance. -- Matthew Garrett | mjg59 at srcf.ucam.org
