block, char_dev: Use correct format specifier for unsigned ints

register_blkdev() and __register_chrdev_region() treat the major
number as an unsigned int. So print it the same way to avoid
absurd error statements such as:
"... major requested (-1) is greater than the maximum (511) ..."
(and also fix off-by-one bugs in the error prints).

While at it, also update the comment describing register_blkdev().
Signed-off-by: Srivatsa S. Bhat <srivatsa@csail.mit.edu>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

block/genhd.c

@@ -308,19 +308,22 @@ void blkdev_show(struct seq_file *seqf, off_t offset)
 /**
  * register_blkdev - register a new block device
  *
- * @major: the requested major device number [1..255]. If @major = 0, try to
- *         allocate any unused major number.
+ * @major: the requested major device number [1..BLKDEV_MAJOR_MAX-1]. If
+ *         @major = 0, try to allocate any unused major number.
  * @name: the name of the new block device as a zero terminated string
  *
  * The @name must be unique within the system.
  *
  * The return value depends on the @major input parameter:
  *
- *  - if a major device number was requested in range [1..255] then the
- *    function returns zero on success, or a negative error code
+ *  - if a major device number was requested in range [1..BLKDEV_MAJOR_MAX-1]
+ *    then the function returns zero on success, or a negative error code
  *  - if any unused major number was requested with @major = 0 parameter
  *    then the return value is the allocated major number in range
- *    [1..255] or a negative error code otherwise
+ *    [1..BLKDEV_MAJOR_MAX-1] or a negative error code otherwise
+ *
+ * See Documentation/admin-guide/devices.txt for the list of allocated
+ * major numbers.
  */
 int register_blkdev(unsigned int major, const char *name)
 {
@@ -347,8 +350,8 @@ int register_blkdev(unsigned int major, const char *name)
 	}
 
 	if (major >= BLKDEV_MAJOR_MAX) {
-		pr_err("register_blkdev: major requested (%d) is greater than the maximum (%d) for %s\n",
-		       major, BLKDEV_MAJOR_MAX, name);
+		pr_err("register_blkdev: major requested (%u) is greater than the maximum (%u) for %s\n",
+		       major, BLKDEV_MAJOR_MAX-1, name);
 
 		ret = -EINVAL;
 		goto out;
@@ -375,7 +378,7 @@ int register_blkdev(unsigned int major, const char *name)
 		ret = -EBUSY;
 
 	if (ret < 0) {
-		printk("register_blkdev: cannot get major %d for %s\n",
+		printk("register_blkdev: cannot get major %u for %s\n",
 		       major, name);
 		kfree(p);
 	}

fs/char_dev.c

@@ -121,8 +121,8 @@ __register_chrdev_region(unsigned int major, unsigned int baseminor,
 	}
 
 	if (major >= CHRDEV_MAJOR_MAX) {
-		pr_err("CHRDEV \"%s\" major requested (%d) is greater than the maximum (%d)\n",
-		       name, major, CHRDEV_MAJOR_MAX);
+		pr_err("CHRDEV \"%s\" major requested (%u) is greater than the maximum (%u)\n",
+		       name, major, CHRDEV_MAJOR_MAX-1);
 		ret = -EINVAL;
 		goto out;
 	}