Acked-by: Zhang Rui <rui.zhang@xxxxxxxxx> On Mon, 2009-08-24 at 22:44 +0800, Stefan Bader wrote: > Zhang Rui wrote: > > On Fri, 2009-08-21 at 18:00 +0800, Stefan Bader wrote: > >> Zhang Rui wrote: > >>> On Thu, 2009-08-20 at 17:14 +0800, Stefan Bader wrote: > >>>> Hardware: Acer 6920G (from a bug report) > >>>> > >>>> Another case of a broken BIOS. In this case there are several definitions for > >>>> video bus devices but only one has _DOS and _DOD defined. All other definitions > >>>> only have _DOD. > >>> I have seen such kind of BIOS too. > >>> > >>>> In the past (2.6.27) _ADR was not evaluated to make sure of using a present > >>>> video device, but with that bug brightness could be changed. > >>>> > >>>> Now the video bus having _DOS and _DOD is detected as not being present. The > >>>> other definitions are not considered because they are lacking the _DOS method. > >>>> Using the attached patch, would cause the detection code to consider the other > >>>> definitions and has been tested to enable backlight control. > >>>> > >>>> Would this be an acceptable approach? > >>> I think so. I generated a similar patch before, but didn't sent it out > >>> for some reason. > >>> My suggestion is that we should also print out a warning message if _DOS > >>> is missed, what do you think? > >> Some indication about the problem can't hurt. Probably not in > >> acpi_is_video_device as that would trigger for even unused devices. > >> So I added a warning to acpi_video_bus_check for the case when _DOS is missing. > > > > how about using printk(KERN_WARNING FW_BUG "blabla")? > > I am not biased on that. > > -Stefan > > thanks, > > rui > > > >> The case of _DOS being present but _DOD not might also be worth a warning but > >> (though the check in acpi_is_video_device prevented this) would have been > >> accepted by the current code. > >> -Stefan > >> > >>> thanks, > >>> rui > >>> > >>>> From the ACPI spec it rather sounds like > >>>> _DOD and _DOS must be present for a device for display switching and _DOS would > >>>> indicate possible backlight control as well. So the question might not be so > >>>> much is it the right thing than is it safe enough to allow more compatibility > >>>> with broken implementations without causing other problems... > >>>> > >>>> -Stefan > >>>> > >> > > > > -- 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
