On 02/11/2013 02:09 PM, Matthew Garrett wrote: > On Mon, Feb 11, 2013 at 01:06:17PM -0600, Seth Forshee wrote: >> On Mon, Feb 11, 2013 at 05:52:13PM +0000, Matthew Garrett wrote: >>> So the problem is that userspace is writing values that don't happen to >>> be aligned with the values the hardware reacts to, and so nothing gets >>> changed? >> >> Yes. The values are valid according to to _BCL, but _BCM is discarding >> any values that aren't contained in an array named BRTW. BRTW is >> literally the object returned by _BCL returns for !Windows 2012. Here's >> a link to the AML if you'd like to take a look. > > Right. My concern here is that Windows clearly doesn't trigger the > issue, and so there's some chance that we'll see similar issues on other > machines. Disabling Windows 8 compatibility isn't really an option. One > choice might be to have the ACPI video driver set all intermediate > values if the system makes the Windows 8 OSI call? Stupid hack idea: what about trying all the levels _BCL reports and seeing which ones change _BQC? Then filter out any that don't really exist. It might make bootup look odd, seeing the backlight quickly scan through all brightness levels, but it's only once per boot. -Ben -- 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
