On 07/31/2013 08:11 AM, Felipe Contreras wrote: > On Tue, Jul 30, 2013 at 6:13 PM, Rafael J. Wysocki <rjw@xxxxxxx> wrote: > >>> If 0 turns the screen off with the intel driver, 0 should turn the >>> screen off with the ACPI driver, having inconsistent behavior >>> depending on which driver is used is a bug. >> >> The ACPI driver simply exposes and interface to interact with the AML methods >> in the BIOS directly. > > No, the ACPI driver is exposing a backlight interface, which has a > defined stable API. > > Documentation/ABI/stable/sysfs-class-backlight > > Yes, the interface doesn't define what should happen at 0, that is a > bug in the interface definition. > > *How* it achieves that is an implementation detail. > >> Yes, this is a mistake and shouldn't be designed this way. >> >> However, incidentally, this makes backlight control work on your machine. >> >> Anyway, we need all backlight drivers to work consistently and don't tempt me >> to rip the ACPI driver entirely from the kernel for what it's worth. > > Yes, they should work consistently, and go ahead, rip the ACPI driver, > *then* you'll see many more people complaining about the Linux kernel > breaking user-space, which should never happen. Mistakes happen, but > if you do this willingly and knowingly, I think there would be > repercussions for you. > >> Yes, that will break backlight on your system and *then* you can complain to >> Linus if you wish. > > It is already broken in v3.11-rc3, in fact I just booted that to try > it out and it booted with the screen completely black (fortunately I > knew exactly what to type to change that). That is bad, can you please file a bug for that? I'll need to take a look at your ACPI tables, thanks. > > Apparently this commit also needs to be reverted: efaa14c (ACPI / > video: no automatic brightness changes by win8-compatible firmware). > In this machine it makes the backlight work again (without > acpi_osi="!Windows 2012"), but by doing so the ACPI driver also turns > off the screen completely at level 0. Also, each time I change the So with rc3 and commit efaa14c reverted, when you set level 0 to ACPI video's backlight interface, the screen will be off now? And this is not the case in 3.10, right? > backlight level from X, the screen blinks as if going 100%, 0%, and > then the desired level. Please attach acpidump output to the to be opened bugzilla page, thanks. -Aaron > > For this particular machine simply applying the attached patch would > solve all those regressions, but who knows in other machines, I think > it's safer to revert efaa14c. > -- 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
