linux-kernel - [PATCH] misc driver: eliminate 256 minor limit & deprecated call register

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Date:	Sun, 16 Dec 2007 17:28:59 +0100
From:	renzo@...unibo.it (Renzo Davoli)
To:	linux-kernel@...r.kernel.org
Subject: [PATCH] misc driver: eliminate 256 minor limit & deprecated call register_chrdev

I already posted this patch on September 9th but nobody cared.

Is anybody interested in knowing that there is an old limit for
misc device minors to 256, that we are terminating the minor numbers,
and that there is a deprecated call in this code?

drivers/char/misc.c: the deprecated call is 
register_chrdev and it limits the number of minors to 256.

I propose this patch that eliminate both problems. With this patch 
misc allocates the entire major 10.

This patch was designed for a previous version of the kernel code
(2.6.22?), I have tested it today and applies to 2.6.24-rc5 with -12
lines offset.

	renzo

Signed-off-by: Renzo Davoli <renzo@...unibo.it>

--- a/drivers/char/misc.c	2007-08-05 16:56:59.000000000 +0200
+++ b/drivers/char/misc.c	2007-09-06 11:07:51.000000000 +0200
@@ -56,6 +56,8 @@
 static LIST_HEAD(misc_list);
 static DEFINE_MUTEX(misc_mtx);
 
+static struct cdev misc_cdev;
+
 /*
  * Assigned numbers, used for dynamic minors
  */
@@ -273,6 +275,31 @@
 EXPORT_SYMBOL(misc_register);
 EXPORT_SYMBOL(misc_deregister);
 
+static int misc_register_chrdev(void)
+{
+	dev_t from=MKDEV(MISC_MAJOR,0);
+	int rv;
+	int err = -ENOMEM;
+	char *s;
+
+	if ((rv=register_chrdev_region(from,MINORMASK,"misc")) != 0)
+		return rv;
+
+	cdev_init(&misc_cdev, &misc_fops);
+	misc_cdev.owner=misc_fops.owner;
+	kobject_set_name(&misc_cdev.kobj, "%s", "misc");
+	for (s = strchr(kobject_name(&misc_cdev.kobj),'/'); s; s = strchr(s, '/'))
+		    *s = '!';
+	err = cdev_add(&misc_cdev, from, MINORMASK);
+	if (err)
+		goto out;
+	return 0;
+out:
+	kobject_put(&misc_cdev.kobj);
+	unregister_chrdev_region(from,MINORMASK);
+  return err;
+}
+
 static int __init misc_init(void)
 {
 #ifdef CONFIG_PROC_FS
@@ -286,7 +313,7 @@
 	if (IS_ERR(misc_class))
 		return PTR_ERR(misc_class);
 
-	if (register_chrdev(MISC_MAJOR,"misc",&misc_fops)) {
+	if (misc_register_chrdev()) {
 		printk("unable to get major %d for misc devices\n",
 		       MISC_MAJOR);
 		class_destroy(misc_class);
--
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