On 08/02/2013 10:41 PM, Rafael J. Wysocki wrote: > On Friday, August 02, 2013 01:55:47 PM Aaron Lu wrote: >> On 03/08/2013 03:39 AM, Seth Forshee wrote: >>> Windows 8 requires all backlight interfaces to report 101 brightness >>> values, and as a result we're starting to see machines with that many >>> brightness levels in _BCL. For machines which send these notifications >>> when the brightness up/down keys are pressed this means a lot of key >>> presses to get any kind of noticeable change in brightness. >>> >>> For a while now we've had the ability to disable in-kernel handling of >>> notifications via the video.brightness_switch_enabled parameter. Change >>> this to default to off, and let userspace choose more reasonable >>> increments for changing the brightness. >> >> I just found one more reason for this param to default 0. > > Do you mean video.brightness_switch_enabled? Yes. > >> We are going to separate the backlight interface control and event >> notification functionalities of the ACPI video module, it is highly >> possible a lot of systems will use a combination of the event >> notification handler and intel_backlight interface. So it doesn't make >> sense to let video module to do any adjustment on its own if user space >> has chosen a different interface to use. Actually, it can cause problems >> as in ASUS's case: >> https://bugzilla.kernel.org/show_bug.cgi?id=52951 >> >> The problem there is, on hotkey brightness up, the video module will >> adjust the brightness level first and since its _BQC is broken, it gets >> a wrong number(too low or too high or whatever) and then does the _BCM >> call. The _BCM method works. Then user space picks the intel_backlight >> to do the adjustment, but since the _BCM already sets a wrong value, the >> user space's adjustment is affected too. The result is, user has only >> two visible levels, very low and very high. >> >> This only occurs on -rc3, since we removed the >> acpi_video_verify_backlight_support from acpi_video_switch_brightness >> function. > > What did we do before -rc2? Did we address that in any way? No, before rc2, backlight is broken on that system. In rc2, we added the win8 patch and a fix patch for the hotkey, then the ACPI video module's backlight control and in kernel brightness handling is disabled. With the working hotkey and intel_backlight, rc2 works for the system. Then with the revert in rc3, user needs to choose intel_backlight in xorg.conf but the in kernel brightness handling from ACPI video module is back. Since video module is broken, it breaks the backlight hotkey functionality. Thanks, Aaron > >> So either we make this param default to 0, or we make a new >> function to avoid brightness switch in video module for Win8 systems. >> >> I prefer to set this param to 0 by default. What do you guys think? > > That depends on what we did earlier. > > Thanks, > Rafael > > -- 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
