On Mon, Feb 11, 2013 at 08:31:08PM +0100, Rafael J. Wysocki wrote: > On Monday, February 11, 2013 07:09:14 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 So my take on this is that it's a transition issue. In the case of the x230 I know that this machine was sold with Windows 7 before Windows 8 came out and that older versions of the firmware don't have the Win8 workaround. I suspect the story is the same with the other models. > > choice might be to have the ACPI video driver set all intermediate > > values if the system makes the Windows 8 OSI call? > > At least I'd prefer that, so it would be great to verify if it works. I expect it will work, depending on your definition of "works." The problem with this suggestion is that there are still going to be instances where a user's desktop says the brightness has changed without it actually changing. For example, gnome-settings-daemon is going to break this down into increments of 5, and even with hitting every point in between some steps aren't going to change the brightness at all. But if disabling Windows 8 compatibility is out then that may be the best we can do without resorting to something really ugly. Seth -- 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
