drivers/char/misc.c: use bitmap/bitops functions for dynamic minor nu…

…mber allocation Use DECLARE_BITMAP(), find_first_zero_bit(), set_bit() and clear_bit() instead of rewriting code to do it with the minor number dynamic allocation bitmap. We need to invert the bit position to keep the code behaviour of using the last minor numbers first, since we don't have a find_last_zero_bit. Signed-off-by: Thadeu Lima de Souza Cascardo <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: Alan Cox <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
yshchan · Dec 15, 2009 · 1f2f38d · 1f2f38d
1 parent 4ae717d
commit 1f2f38d
Showing 1 changed file with 9 additions and 13 deletions.
diff --git a/drivers/char/misc.c b/drivers/char/misc.c
@@ -60,7 +60,7 @@ static DEFINE_MUTEX(misc_mtx);
  * Assigned numbers, used for dynamic minors
  */
 #define DYNAMIC_MINORS 64 /* like dynamic majors */
-static unsigned char misc_minors[DYNAMIC_MINORS / 8];
+static DECLARE_BITMAP(misc_minors, DYNAMIC_MINORS);
 
 #ifdef CONFIG_PROC_FS
 static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
@@ -196,27 +196,23 @@ int misc_register(struct miscdevice * misc)
 	}
 
 	if (misc->minor == MISC_DYNAMIC_MINOR) {
-		int i = DYNAMIC_MINORS;
-		while (--i >= 0)
-			if ( (misc_minors[i>>3] & (1 << (i&7))) == 0)
-				break;
-		if (i<0) {
+		int i = find_first_zero_bit(misc_minors, DYNAMIC_MINORS);
+		if (i >= DYNAMIC_MINORS) {
 			mutex_unlock(&misc_mtx);
 			return -EBUSY;
 		}
-		misc->minor = i;
+		misc->minor = DYNAMIC_MINORS - i - 1;
+		set_bit(i, misc_minors);
 	}
 
-	if (misc->minor < DYNAMIC_MINORS)
-		misc_minors[misc->minor >> 3] |= 1 << (misc->minor & 7);
 	dev = MKDEV(MISC_MAJOR, misc->minor);
 
 	misc->this_device = device_create(misc_class, misc->parent, dev,
 					  misc, "%s", misc->name);
 	if (IS_ERR(misc->this_device)) {
-		int i = misc->minor;
+		int i = DYNAMIC_MINORS - misc->minor - 1;
 		if (i < DYNAMIC_MINORS && i >= 0)
-			misc_minors[i>>3] &= ~(1 << (i & 7));
+			clear_bit(i, misc_minors);
 		err = PTR_ERR(misc->this_device);
 		goto out;
 	}
@@ -243,7 +239,7 @@ int misc_register(struct miscdevice * misc)
 
 int misc_deregister(struct miscdevice *misc)
 {
-	int i = misc->minor;
+	int i = DYNAMIC_MINORS - misc->minor - 1;
 
 	if (list_empty(&misc->list))
 		return -EINVAL;
@@ -252,7 +248,7 @@ int misc_deregister(struct miscdevice *misc)
 	list_del(&misc->list);
 	device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
 	if (i < DYNAMIC_MINORS && i >= 0)
-		misc_minors[i>>3] &= ~(1 << (i & 7));
+		clear_bit(i, misc_minors);
 	mutex_unlock(&misc_mtx);
 	return 0;
 }