[PATCH][BUG] Fix the graphic corruption issue on IA64 machines

[izumi <izumi2005@soft.fujitsu.com>]

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Hi,

I encountered the graphic corruption issue on IA64 machines by the
following operations.

 0. enable VGA console(default setting). disable serial console setting.
 1. boot the system at run level 3 and login via text-mode console
(/dev/tty1)
    as the root user.
 2. disable console blanking.
    # setterm -blank 0
 3. start X.
 4. shutdown X.
 5. start X again.
 6. open the gnome-terminal and write someting to /dev/console.
    # ls -l  > /dev/console

The cause of this problem may be VGA console driver's misunderstanding
mode(text/graphic).

I confirmed this problem is fixed by the attached patch, but I don't
know this is the correct fix.

--------------------------------------------------------------------

VGA console driver can misunderstand the current mode(Text/Graphic) under
"disable console blanking" setting.

- start X
  -->  vt_ioctl()    drivers/char/vt_ioctl.c
        do_blank_screen(1)     drivers/char/vt.c
           sw->con_blank(vc_cons[currcons].d, 1, 0)  drivers/char/vt.c
       vgacon_blank()     drivers/video/console/vgacon.c
　        vga_is_gfx = 1 /* enter Graphic mode */

- shutdown X
  -->   vt_ioctl()
          do_unblank_screen(1)    drivers/char/vt.c
            sw->con_blank(vc_cons[currcons].d, 0, leaving_gfx)
        vgacon_blank()
　         vga_is_gfx = 0 /* leave Graphic mode */

When "disable console blank" is set (=> blankinterval=0),
"do_unblank_screen()" function
returns without changing "blank_state", and when "blank_state" is
"blank_off",
"do_blank_screen() function returns without invoking sw->con_blank()
function.
That's why VGA console driver can misunderstand the current mode.

-----------------------------------------------------------------------

Regards,
Taku Izumi


[-- Attachment #2: vt-blank.patch --]
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Fix the graphic corruption issue on IA64 machines.
VGA console driver can misunderstand the current mode(Text/Graphic) under 
"disable console blanking" setting. When "disable console blank" is set (blankinterval=0), "do_unblank_screen()" function returns without changing "blank_state", and when "blank_state" is "blank_off", "do_blank_screen() function returns without invoking sw->con_blank() function. That's why VGA console driver can misunderstand the current mode.

Signed-off-by: Nobuhiro Tachino <ntachino@redhat.com>
Signed-off-by: Taku Izumi <izumi2005@soft.fujitsu.com>
---
 drivers/char/vt.c |    2 +-
 1 files changed, 1 insertion(+), 1 deletion(-)


Index: linux-2.6.21.5/drivers/char/vt.c
========================================================================
--- linux-2.6.21.5.org/drivers/char/vt.c	2007-06-13 12:03:11.000000000 +0900
+++ linux-2.6.21.5/drivers/char/vt.c	2007-06-13 12:07:48.000000000 +0900
@@ -3419,12 +3419,12 @@ void do_unblank_screen(int leaving_gfx)
 		return;
 	}
 	vc = vc_cons[fg_console].d;
+	blank_state = blank_normal_wait;
 	if (vc->vc_mode != KD_TEXT)
 		return; /* but leave console_blanked != 0 */
 
 	if (blankinterval) {
 		mod_timer(&console_timer, jiffies + blankinterval);
-		blank_state = blank_normal_wait;
 	}
 
 	console_blanked = 0;