linux-kernel - [PATCH 2/2] block, char_dev: Use correct format specifier for unsigned ints

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Message-ID: <151788391701.28069.13145257664735983272.stgit@srivatsa-ubuntu>
Date:   Mon, 05 Feb 2018 18:25:27 -0800
From:   "Srivatsa S. Bhat" <srivatsa@...il.mit.edu>
To:     gregkh@...uxfoundation.org, logang@...tatee.com
Cc:     axboe@...nel.dk, jlayton@...chiereds.net, bfields@...ldses.org,
        viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        srivatsa@...il.mit.edu
Subject: [PATCH 2/2] block,
 char_dev: Use correct format specifier for unsigned ints

From: Srivatsa S. Bhat <srivatsa@...il.mit.edu>

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@...il.mit.edu>
---

 block/genhd.c |   19 +++++++++++--------
 fs/char_dev.c |    4 ++--
 2 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index 88a53c1..21a18e5 100644
--- a/block/genhd.c
+++ b/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);
 	}
diff --git a/fs/char_dev.c b/fs/char_dev.c
index 33c9385..a279c58 100644
--- a/fs/char_dev.c
+++ b/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;
 	}