[PATCH] fbdev: Fix crashes in various fbdev's blank routines

The backlight changes that went in had a bug where they could cause the
kernel to access an unitialized pointer when blanking if there is no
backlight control on a machine.

The bug affects atyfb, aty128fb, nvidiafb and rivafb.  radeonfb seems to
be ok.  This fixes it.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

drivers/video/aty/aty128fb.c

@@ -1800,6 +1800,9 @@ static struct backlight_properties aty128_bl_data = {
 
 static void aty128_bl_set_power(struct fb_info *info, int power)
 {
+	if (info->bl_dev == NULL)
+		return;
+
 	mutex_lock(&info->bl_mutex);
 	up(&info->bl_dev->sem);
 	info->bl_dev->props->power = power;
@@ -1828,7 +1831,7 @@ static void aty128_bl_init(struct aty128fb_par *par)
 	bd = backlight_device_register(name, par, &aty128_bl_data);
 	if (IS_ERR(bd)) {
 		info->bl_dev = NULL;
-		printk("aty128: Backlight registration failed\n");
+		printk(KERN_WARNING "aty128: Backlight registration failed\n");
 		goto error;
 	}
 

drivers/video/aty/atyfb_base.c

@@ -2199,6 +2199,9 @@ static struct backlight_properties aty_bl_data = {
 
 static void aty_bl_set_power(struct fb_info *info, int power)
 {
+	if (info->bl_dev == NULL)
+		return;
+
 	mutex_lock(&info->bl_mutex);
 	up(&info->bl_dev->sem);
 	info->bl_dev->props->power = power;
@@ -2223,7 +2226,7 @@ static void aty_bl_init(struct atyfb_par *par)
 	bd = backlight_device_register(name, par, &aty_bl_data);
 	if (IS_ERR(bd)) {
 		info->bl_dev = NULL;
-		printk("aty: Backlight registration failed\n");
+		printk(KERN_WARNING "aty: Backlight registration failed\n");
 		goto error;
 	}
 

drivers/video/nvidia/nv_backlight.c

@@ -112,6 +112,8 @@ static struct backlight_properties nvidia_bl_data = {
 
 void nvidia_bl_set_power(struct fb_info *info, int power)
 {
+	if (info->bl_dev == NULL)
+		return;
 	mutex_lock(&info->bl_mutex);
 	up(&info->bl_dev->sem);
 	info->bl_dev->props->power = power;
@@ -140,7 +142,7 @@ void nvidia_bl_init(struct nvidia_par *par)
 	bd = backlight_device_register(name, par, &nvidia_bl_data);
 	if (IS_ERR(bd)) {
 		info->bl_dev = NULL;
-		printk("nvidia: Backlight registration failed\n");
+		printk(KERN_WARNING "nvidia: Backlight registration failed\n");
 		goto error;
 	}
 

drivers/video/riva/fbdev.c

@@ -354,6 +354,9 @@ static struct backlight_properties riva_bl_data = {
 
 static void riva_bl_set_power(struct fb_info *info, int power)
 {
+	if (info->bl_dev == NULL)
+		return;
+
 	mutex_lock(&info->bl_mutex);
 	up(&info->bl_dev->sem);
 	info->bl_dev->props->power = power;
@@ -382,7 +385,7 @@ static void riva_bl_init(struct riva_par *par)
 	bd = backlight_device_register(name, par, &riva_bl_data);
 	if (IS_ERR(bd)) {
 		info->bl_dev = NULL;
-		printk("riva: Backlight registration failed\n");
+		printk(KERN_WARNING "riva: Backlight registration failed\n");
 		goto error;
 	}