On Saturday, October 12, 2013 02:53:38 AM Igor Gnatenko wrote: > On Sat, 2013-10-12 at 00:45 +0200, Rafael J. Wysocki 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 <rjw@xxxxxxxxxxxxx> 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.lu@xxxxxxxxx> 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. > > > > Well, adding a Kconfig option should be simple enough, but I'm not sure > > I understand the point. You'll still need to rebuild the kernel after changing > > that option. > > > > I think he meant that we should have Kconfig option alike > CONFIG_I915_BACKLIGHT_UNREGISTER which have true or false. > If it true - unregister acpi backlight as default. > I think so. That's my understanding too, but I'm not sure about the benefit. The only one seems to be that distros wanting to change the default won't have to carry a patch for that. Thanks! -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
