The AML implementation for brightness control on several ThinkPads contains a workaround to meet a Windows 8 requirement of 101 brightness levels [1]. The implementation is flawed, as only 16 of the brighness values reported by _BCL affect a change in brightness. _BCM silently discards the rest of the values. Disabling Windows 8 compatibility on these machines reverts them to the old behavior, making _BCL only report the 16 brightness levels which actually work. Add a quirk to do this along with a dmi callback to disable Win8 compatibility. [1] http://msdn.microsoft.com/en-us/library/windows/hardware/jj128256.aspx Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=51231 BugLink: http://bugs.launchpad.net/bugs/1098216 Signed-off-by: Seth Forshee <seth.forshee@xxxxxxxxxxxxx> --- This has been discussed previously at [2], however the description of the problem there is incorrect. _BCM simply discards any value written that isn't one of the brightness levels returned by _BCL for non-Win8 systems; it does not do any rounding. This patch quirks six machines that have been confirmed to have this problem, but there may be others. I looked for some way to do this other than quirking for individual models, but unfortunately I couldn't find any other criteria which worked. Thanks, Seth [2] http://comments.gmane.org/gmane.linux.acpi.devel/58398 drivers/acpi/blacklist.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 62 insertions(+) diff --git a/drivers/acpi/blacklist.c b/drivers/acpi/blacklist.c index cb96296..6c242ed 100644 --- a/drivers/acpi/blacklist.c +++ b/drivers/acpi/blacklist.c @@ -193,6 +193,13 @@ static int __init dmi_disable_osi_win7(const struct dmi_system_id *d) return 0; } +static int __init dmi_disable_osi_win8(const struct dmi_system_id *d) +{ + printk(KERN_NOTICE PREFIX "DMI detected: %s\n", d->ident); + acpi_osi_setup("!Windows 2012"); + return 0; +} + static struct dmi_system_id acpi_osi_dmi_table[] __initdata = { { .callback = dmi_disable_osi_vista, @@ -269,6 +276,61 @@ static struct dmi_system_id acpi_osi_dmi_table[] __initdata = { }, /* + * The following Lenovo models have a broken workaround in the + * acpi_video backlight implementation to meet the Windows 8 + * requirement of 101 backlight levels. Reverting to pre-Win8 + * behavior fixes the problem. + */ + { + .callback = dmi_disable_osi_win8, + .ident = "Lenovo ThinkPad L430", + .matches = { + DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"), + DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad L430"), + }, + }, + { + .callback = dmi_disable_osi_win8, + .ident = "Lenovo ThinkPad T430s", + .matches = { + DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"), + DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad T430s"), + }, + }, + { + .callback = dmi_disable_osi_win8, + .ident = "Lenovo ThinkPad T530", + .matches = { + DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"), + DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad T530"), + }, + }, + { + .callback = dmi_disable_osi_win8, + .ident = "Lenovo ThinkPad W530", + .matches = { + DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"), + DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad W530"), + }, + }, + { + .callback = dmi_disable_osi_win8, + .ident = "Lenovo ThinkPad X1 Carbon", + .matches = { + DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"), + DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad X1 Carbon"), + }, + }, + { + .callback = dmi_disable_osi_win8, + .ident = "Lenovo ThinkPad X230", + .matches = { + DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"), + DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad X230"), + }, + }, + + /* * BIOS invocation of _OSI(Linux) is almost always a BIOS bug. * Linux ignores it, except for the machines enumerated below. */ -- 1.7.9.5 -- 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
