On 07/30/2013 01:51 PM, Aaron Lu wrote: > On 07/30/2013 11:44 AM, Felipe Contreras wrote: >> On Mon, Jul 29, 2013 at 10:11 PM, Aaron Lu <aaron.lwe@xxxxxxxxx> wrote: >>> On 07/30/2013 03:20 AM, Felipe Contreras wrote: >>>> Since v3.7 the acpi backlight driver doesn't work at all on this machine >>>> because presumably the ACPI code contains stub code when Windows 8 OSI is >>>> reported. >>>> >>>> The commit ea45ea7 (in v3.11-rc2) tried to fix this problem by using the intel >>>> backlight driver, however, on this machine it turns the backlight completely >>>> off when it reaches level 0%, after which the user might have a lot trouble >>>> trying to bring it back. >>> >>> What do you mean by a lot of trouble? If you press hotkey to increase >>> backlight brightness level, does it work? >> >> I guess so, *if* there is indeed a user-space power manager handling >> that, *and* the keyboard has such keys, *or* the user has set custom >> hotkeys. > > Right, for a GUI environment this may not be a big problem(user uses Fn > key to decrease brightness level and then hit the black screen, it's > natural he will use Fn key to increase brightness level). > >> >>> If so, the screen should not >>> be black any more, it's not that user has to blindly enter some command >>> to get out of the black screen. >>> >>> And I'm not sure if this is a bug of intel_backlight(setting a low level >>> makes the screen almost off), I see different models with different >>> vendors having this behavior. >> >> I mean, the screen is completely off, I cannot see absolutely >> anything. I don't see this behavior with the ACPI backlight driver, >> nor do I see that in Windows 7. >> >>> If this is deemed a bug, then I'm afraid >>> intel_backlight interface is useless for a lot of systems...perhaps we >>> can only say, intel_backlight's interpretation of low levels are >>> different with ACPI video's, and that's probably why its type is named >>> as raw :-) >> >> Well, a bug is defined as unexpected behavior -- as a user, if I'm >> changing the brightness of the screen, I certainly don't expect the >> screen to turn off, and I think that's the expectation from most >> people. It's the first time I see something like that. > > I agree this is kind of un-expected. At the same time, this seems to be > the normal behavior for intel_backlight. I don't know what the correct > thing to do here if this is something we want to avoid - modify intel > backlight handling code not to set too low value or change the user > space tool not to set a too low value if they are interacting with a > raw type interface. Neither of them sounds cool... Or, users may get > used to it, I for example, don't find this to be very annoying, but > maybe I'm already used to it. BTW, for the complete screen off problem, I don't see there is anything wrong with it from code's point of view. It's not that there is an error in code or this is a broken hardware that caused the screen off when setting a very low or 0 brightness level, it is simply the expected behavior of what this interface can provide. It can really set the brightness level to minimum(zero) or maximum. Don't get me wrong, I didn't mean this is a good user experience, I don't know that. I just don't think this is a program bug, and I don't know if this should be fixed or not - obviously this interface did what it is asked to do, correctly. Thanks, Aaron -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
