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

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Date:	Thu, 14 Jun 2007 11:26:33 +0900
From:	izumi <izumi2005@...t.fujitsu.com>
To:	linux-kernel@...r.kernel.org
Subject: [PATCH][BUG] Fix the graphic corruption issue on IA64 machines

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

View attachment "vt-blank.patch" of type "text/plain" (1295 bytes)