Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=a21101c46ca5b4320e31408853cdcbf7cb1ce4ed
Commit:     a21101c46ca5b4320e31408853cdcbf7cb1ce4ed
Parent:     c2f828977ba5d17c13debba374ea252d18e5ccfb
Author:     Zhang Rui <[EMAIL PROTECTED]>
AuthorDate: Fri Sep 14 11:46:22 2007 +0800
Committer:  Len Brown <[EMAIL PROTECTED]>
CommitDate: Tue Sep 18 13:37:49 2007 -0400

    ACPI: video: _DOS=0 by default to prevent hotkey hang
    
    In the past, the Linux/ACPI video driver invoked _DOS
    (Display Output Switch) with the parameter 1
    to tell the BIOS to switch the video output display for us.
    
    But this conflicts with Linux native graphics drivers,
    and can cause all sorts of issues, including hanging the system.
    
    http://bugzilla.kernel.org/show_bug.cgi?id=6001
    
    Here we change the Linux default to evaluate _DOS=0,
    which tells the BIOS to simply send us a hotkey event
    and not touch the graphics hardware.
    
    The acpi video driver sends the display switch hotkey
    event up through the intput layer, and X can interpret
    that and use its native graphics driver to switch the display.
    
    For the case where Linux has no native graphics driver running,
    or the graphics driver doesn't know how to switch video and
    the BIOS (safely) does, the previous behaviour can be restored with:
    
    # echo 1 > /proc/acpi/video/*/DOS
    
    Signed-off-by: Zhang Rui <[EMAIL PROTECTED]>
    Signed-off-by: Len Brown <[EMAIL PROTECTED]>
---
 drivers/acpi/video.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index 3c9bb85..6cb3e7b 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -1754,7 +1754,7 @@ static int acpi_video_bus_put_devices(struct 
acpi_video_bus *video)
 
 static int acpi_video_bus_start_devices(struct acpi_video_bus *video)
 {
-       return acpi_video_bus_DOS(video, 1, 0);
+       return acpi_video_bus_DOS(video, 0, 0);
 }
 
 static int acpi_video_bus_stop_devices(struct acpi_video_bus *video)
-
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