[PATCH] cfag12864b: fix crash when built-in and no parport present

The problem comes when ks0108/cfag12864b are built-in and no parallel port is
present.  ks0108_init() is called first, as it should be, but fails to load
(as there is no parallel port to use).

After that, cfag12864b_init() gets called, without knowing anything about
ks0108 failed, and calls ks0108_writecontrol(), which dereferences an
uninitialized pointer.

Init order is OK, I think.  The problem is how to stop cfag12864b_init() being
called if ks0108 failed to load.  modprobe does it for us, but, how when
built-in?

Signed-off-by: Miguel Ojeda Sandonis <maxextreme@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 1 deletions

diff --git a/drivers/auxdisplay/cfag12864bfb.c b/drivers/auxdisplay/cfag12864bfb.c
index 94765e78315f..66fafbb1d087 100644
--- a/drivers/auxdisplay/cfag12864bfb.c
+++ b/drivers/auxdisplay/cfag12864bfb.c
@@ -137,7 +137,14 @@ static struct platform_device *cfag12864bfb_device;
 
 static int __init cfag12864bfb_init(void)
 {
-        int ret;
+        int ret = -EINVAL;
+
+        /* cfag12864b_init() must be called first */
+        if (!cfag12864b_isinited()) {
+                printk(KERN_ERR CFAG12864BFB_NAME ": ERROR: "
+                        "cfag12864b is not initialized\n");
+                goto none;
+        }
 
         if (cfag12864b_enable()) {
                 printk(KERN_ERR CFAG12864BFB_NAME ": ERROR: "
@@ -162,6 +169,7 @@ static int __init cfag12864bfb_init(void)
                 }
         }
 
+none:
         return ret;
 }