On 10/01/2014 04:18 AM, Rafael J. Wysocki wrote: > On Tuesday, September 30, 2014 02:10:17 PM Aaron Lu wrote: >> The _DOD method lists which video output device is currently attached so >> we should only care about them and ignore others. An user recently >> reported that there are two acpi_video interfaces appeared on his system >> and one of them doesn't work. From the acpidump, it is found that there >> are more than one video output devices that have _BCM control method but >> the _DOD lists only one of them. So this patch checks if the video output >> device is in the _DOD list and will not create backlight device if it is >> not in the list. Also, we consider the broken _DOD case(reflected by the >> video->attached_count is 0) and do not change behaviour for those broken >> _DOD systems. >> >> Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=84111 >> Reported-and-tested-by: ntrrgc@xxxxxxxxx >> Signed-off-by: Aaron Lu <aaron.lu@xxxxxxxxx> > > This looks reasonable to me, but I'm a little afraid that it may break > systems which forget to list valid interfaces in the _DOD. Indeed, this is possible. > > For this reason, I'm queuing this up for 3.18, but not for -stable. Agree. > > We can request a backport after a while when we're reasonably sure that > there are no regressions resulting from this. Sounds good, thanks for taking care of this! Regards, Aaron > >> --- >> drivers/acpi/video.c | 26 ++++++++++++++++++++++++++ >> 1 file changed, 26 insertions(+) >> >> diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c >> index 7285c7f9a935..807a88a0f394 100644 >> --- a/drivers/acpi/video.c >> +++ b/drivers/acpi/video.c >> @@ -1154,6 +1154,23 @@ acpi_video_device_bind(struct acpi_video_bus *video, >> } >> } >> >> +static bool acpi_video_device_in_dod(struct acpi_video_device *device) >> +{ >> + struct acpi_video_bus *video = device->video; >> + int i; >> + >> + /* If we have a broken _DOD, no need to test */ >> + if (!video->attached_count) >> + return true; >> + >> + for (i = 0; i < video->attached_count; i++) { >> + if (video->attached_array[i].bind_info == device) >> + return true; >> + } >> + >> + return false; >> +} >> + >> /* >> * Arg: >> * video : video bus device >> @@ -1593,6 +1610,15 @@ static void acpi_video_dev_register_backlight(struct acpi_video_device *device) >> static int count; >> char *name; >> >> + /* >> + * Do not create backlight device for video output >> + * device that is not in the enumerated list. >> + */ >> + if (!acpi_video_device_in_dod(device)) { >> + dev_dbg(&device->dev->dev, "not in _DOD list, ignore\n"); >> + return; >> + } >> + >> result = acpi_video_init_brightness(device); >> if (result) >> return; >> > -- 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
