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Subject[013/136] fbcon: only unbind from console if successfully registered
2.6.31-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Ian Armstrong <ian@iarmst.demon.co.uk>

commit 2ddce3fd0acbdc1be684fb5f919ae3d2e9518aac upstream.

Attempting to unload a framebuffer module calls unregister_framebuffer()
which in turn gets fbcon to release it. If fbcon has no framebuffers
linked to a console, it will also unbind itself from the console driver.
However, if fbcon never registered itself as a console driver, the unbind
will fail causing the framebuffer device entry to persist. In most cases
this failure will result in an oops when attempting to access the now
non-existent device.

This patch ensures that the fbcon unbind request will succeed even if a
bind was never done. It tracks if a successful bind ever occurred & will
only attempt to unbind if needed. If there never was a bind, it simply
returns with no error.

Signed-off-by: Ian Armstrong <ian@iarmst.demon.co.uk>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/video/console/fbcon.c | 10 ++++++++++
1 file changed, 10 insertions(+)

--- a/drivers/video/console/fbcon.c
+++ b/drivers/video/console/fbcon.c
@@ -114,6 +114,7 @@ static int last_fb_vc = MAX_NR_CONSOLES
static int fbcon_is_default = 1;
static int fbcon_has_exited;
static int primary_device = -1;
+static int fbcon_has_console_bind;

#ifdef CONFIG_FRAMEBUFFER_CONSOLE_DETECT_PRIMARY
static int map_override;
@@ -544,6 +545,8 @@ static int fbcon_takeover(int show_logo)
con2fb_map[i] = -1;
}
info_idx = -1;
+ } else {
+ fbcon_has_console_bind = 1;
}

return err;
@@ -2923,6 +2926,10 @@ static int fbcon_unbind(void)

ret = unbind_con_driver(&fb_con, first_fb_vc, last_fb_vc,
fbcon_is_default);
+
+ if (!ret)
+ fbcon_has_console_bind = 0;
+
return ret;
}
#else
@@ -2936,6 +2943,9 @@ static int fbcon_fb_unbind(int idx)
{
int i, new_idx = -1, ret = 0;

+ if (!fbcon_has_console_bind)
+ return 0;
+
for (i = first_fb_vc; i <= last_fb_vc; i++) {
if (con2fb_map[i] != idx &&
con2fb_map[i] != -1) {



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