On Wed, 2008-04-02 at 22:53 +0400, Andrey Borzenkov wrote: > Commit 7c0ea45be4f114d85ee35caeead8e1660699c46f registers ACPI backlight > even if _BQC method (query current backlight level) is missing. The effect is: > > during initialization video.c:acpi_video_device_find_cap() calls backlight_update_status(). It tries to fetch actual level via acpi_video_get_brightness() - but as _BQC is missing it just returns current value > as stored in memory - i.e. zero, because it was never set. So effectively > backlight_update_status() reset brightness to minimal value == 0. > > This happens on Toshiba Portege 4000. Verified by reverting commit on top of > rc8. It seems that _BQC object is missing on the Toshiba Portege 4000. And acpi video driver will continue to update the status of backlight even when _BQC object is missing, which is inappropriate. Maybe it is more appropriate that OS doesn't update the status of backlight in boot phase when _BQC object is missing. Of course please attach the output of acpidump in kernel bugzilla. http://bugzilla.kernel.org/show_bug.cgi?id=10387 > On a side note, it would be nice to fit backlight device into actual ACPI > device tree instead of /devices/virtual. -- 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
