On Saturday, October 12, 2013 08:34:32 AM Seth Forshee wrote: > On Sat, Oct 12, 2013 at 04:44:30AM -0700, Josh Boyer wrote: > > On Fri, Oct 11, 2013 at 4:27 PM, Rafael J. Wysocki <r...@rjwysocki.net> > > wrote: > > > On Friday, October 11, 2013 06:01:43 PM Josh Boyer wrote: > > >> On Fri, Oct 11, 2013 at 6:10 PM, Rafael J. Wysocki <r...@rjwysocki.net> > > >> wrote: > > >> > On Friday, October 11, 2013 12:42:43 PM Josh Boyer wrote: > > >> >> On Fri, Oct 11, 2013 at 9:27 AM, Aaron Lu <aaron...@intel.com> wrote: > > >> >> > v5: > > >> >> > 1 Introduce video.use_native_backlight module parameter and set its > > >> >> > value to false by default as suggested by Rafael. For Win8 systems > > >> >> > which have broken ACPI video backlight control, the parameter can > > >> >> > be > > >> >> > set to 1 in kernel cmdline to skip registering ACPI video's > > >> >> > backlight > > >> >> > interface. Due to this change, the > > >> >> > acpi_video_verify_backlight_support > > >> >> > is moved from video_detect.c to video.c - patch 3/4; > > >> >> > > >> >> That's a fairly untenable position for distro kernels to be in. They > > >> >> now have to ask every user that reports an issue with the backlight to > > >> >> try setting that option on the command line. While I appreciate the > > >> >> setting breaks things for some people, doesn't the Win8 issue impact > > >> >> far more people? Shouldn't it be defaulted to true? > > >> > > > >> > Well, we have a rule in the kernel not to introduce regressions for > > >> > users even > > >> > if they are minority. > > >> > > > >> >> If nothing else, can you add a config option for the default so > > >> >> distros can use that to decide which way to default it and then work > > >> >> on fixing the remaining users that have troubles? > > >> > > > >> > The current plan is to create a blacklist of systems where that option > > >> > should > > >> > be set. We actually already have one, but it is at the _OSI() level, > > >> > which > > >> > is overkill in my view and may affect things beyond backlight. Along > > >> > with that > > >> > we will debug systems where setting that option (to true) causes > > >> > problems to > > >> > happen, so that we'll be able to drop it going forward (hopefully). > > >> > > > >> > Of course, distro kernels may always change the default to true if > > >> > they want. > > >> > > >> They can, but they'd need to either patch the kernel to do so, or code > > >> it in userspace bootloader configs. Having a config option they can > > >> set to change the default makes it reasonable and contained within the > > >> kernel. > > > > > > If we are to use a Kconfig option, why don't we use one instead of rather > > > than > > > in addition to a command line option? Say, we have > > > CONFIG_ACPI_VIDEO_WIN8_WORKAROUND and if that is set, the code will work > > > like > > > the previous version of the Aaron's patchset (the one without > > > video.use_native_backlight)? > > > > > > Opinions? > > > > If you only have a config option, users can't override the distro > > settings. If you simply have a config option for the default value, > > the distros can set it without having to carry a patch (the primary > > benefit), but users can still override that without having to rebuild > > a kernel. > > It sounds like the blacklist and the default value of the parameter > would be inherently tied together, i.e. the blacklist essentially > overrides the default value for specific machines. So when the config > option were flipped from its default the blacklist wouldn't work > anymore, and you'd need a second blacklist for machines which require > video.use_native_backlight=n. I doubt anyone wants to see that happen, > so I think we have to pick one value or the other for the default and > make it configurable only via the command line.
Good point. Thanks! -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx
