On 02/12/2013 12:21 AM, Seth Forshee wrote: > 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. If we disable the _BQC(i.e. set cap._BQC=0) for these systems, will the problem go away? If so, I think perhaps we can put these systems into a _BQC quirk table and set cap._BQC=0 for them. Thanks, Aaron > > [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. > */ > -- 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
