| Message ID | 4A92A73C.7010003@canonical.com (mailing list archive) |
|---|---|
| State | RFC, archived |
| Headers | show |
Acked-by: Zhang Rui <rui.zhang@intel.com> 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@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
From 6b483015524f67dee3ae2f08f3c0cef27c9d84c6 Mon Sep 17 00:00:00 2001 From: Stefan Bader <stefan.bader@canonical.com> Date: Fri, 21 Aug 2009 11:03:05 +0200 Subject: [PATCH] acpi: video: Loosen strictness of video bus detection code BugLink: http://bugs.launchpad.net/bugs/333386 Currently a video bus device must (beside other criteria) define _DOD and _DOS methods to be considered a video device. Some broken BIOSes prevented working backlight control by only defining both for one (non-existing bus) and only _DOD for the rest. With this patch in place the other bus definitions were considered too and backlight control started to work again. Signed-off-by: Stefan Bader <stefan.bader@canonical.com> --- drivers/acpi/video.c | 7 ++++++- drivers/acpi/video_detect.c | 2 +- 2 files changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c index 8851315..acd4636 100644 --- a/drivers/acpi/video.c +++ b/drivers/acpi/video.c @@ -1083,7 +1083,12 @@ static int acpi_video_bus_check(struct acpi_video_bus *video) */ /* Does this device support video switching? */ - if (video->cap._DOS) { + if (video->cap._DOS || video->cap._DOD) { + if (!video->cap._DOS) { + printk(KERN_WARNING FW_BUG + "ACPI(%s) defines _DOD but not _DOS\n", + acpi_device_bid(video->device)); + } video->flags.multihead = 1; status = 0; } diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c index 7cd2b63..bee5e34 100644 --- a/drivers/acpi/video_detect.c +++ b/drivers/acpi/video_detect.c @@ -82,7 +82,7 @@ long acpi_is_video_device(struct acpi_device *device) return 0; /* Does this device able to support video switching ? */ - if (ACPI_SUCCESS(acpi_get_handle(device->handle, "_DOD", &h_dummy)) && + if (ACPI_SUCCESS(acpi_get_handle(device->handle, "_DOD", &h_dummy)) || ACPI_SUCCESS(acpi_get_handle(device->handle, "_DOS", &h_dummy))) video_caps |= ACPI_VIDEO_OUTPUT_SWITCHING; -- 1.5.4.3