chardev: code cleanup for __register_chrdev_region()

It's just code cleanup, not functional change.

Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/char_dev.c b/fs/char_dev.c
index 6803e98414f1a9c6fc1f512bec3c528b6643754c..bd2bf1fd847e43495e499091db9df1d071579bdf 100644 (file)
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -100,10 +100,16 @@ static struct char_device_struct *
 __register_chrdev_region(unsigned int major, unsigned int baseminor,
                           int minorct, const char *name)
 {
-       struct char_device_struct *cd, **cp;
-       int ret = 0;
+       struct char_device_struct *cd, *curr, *prev = NULL;
+       int ret = -EBUSY;
        int i;
 
+       if (major >= CHRDEV_MAJOR_MAX) {
+               pr_err("CHRDEV \"%s\" major requested (%u) is greater than the maximum (%u)\n",
+                      name, major, CHRDEV_MAJOR_MAX-1);
+               return ERR_PTR(-EINVAL);
+       }
+
        if (minorct > MINORMASK + 1 - baseminor) {
                pr_err("CHRDEV \"%s\" minor range requested (%u-%u) is out of range of maximum range (%u-%u) for a single major\n",
                        name, baseminor, baseminor + minorct - 1, 0, MINORMASK);
@@ -126,55 +132,36 @@ __register_chrdev_region(unsigned int major, unsigned int baseminor,
                major = ret;
        }
 
-       if (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;
-       }
-
-       cd->major = major;
-       cd->baseminor = baseminor;
-       cd->minorct = minorct;
-       strlcpy(cd->name, name, sizeof(cd->name));
-
        i = major_to_index(major);
+       for (curr = chrdevs[i]; curr; prev = curr, curr = curr->next) {
+               if (curr->major < major)
+                       continue;
 
-       for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
-               if ((*cp)->major > major ||
-                   ((*cp)->major == major &&
-                    (((*cp)->baseminor >= baseminor) ||
-                     ((*cp)->baseminor + (*cp)->minorct > baseminor))))
+               if (curr->major > major)
                        break;
 
-       /* Check for overlapping minor ranges.  */
-       if (*cp && (*cp)->major == major) {
-               int old_min = (*cp)->baseminor;
-               int old_max = (*cp)->baseminor + (*cp)->minorct - 1;
-               int new_min = baseminor;
-               int new_max = baseminor + minorct - 1;
+               if (curr->baseminor + curr->minorct <= baseminor)
+                       continue;
 
-               /* New driver overlaps from the left.  */
-               if (new_max >= old_min && new_max <= old_max) {
-                       ret = -EBUSY;
-                       goto out;
-               }
+               if (curr->baseminor >= baseminor + minorct)
+                       break;
 
-               /* New driver overlaps from the right.  */
-               if (new_min <= old_max && new_min >= old_min) {
-                       ret = -EBUSY;
-                       goto out;
-               }
+               goto out;
+       }
 
-               if (new_min < old_min && new_max > old_max) {
-                       ret = -EBUSY;
-                       goto out;
-               }
+       cd->major = major;
+       cd->baseminor = baseminor;
+       cd->minorct = minorct;
+       strlcpy(cd->name, name, sizeof(cd->name));
 
+       if (!prev) {
+               cd->next = curr;
+               chrdevs[i] = cd;
+       } else {
+               cd->next = prev->next;
+               prev->next = cd;
        }
 
-       cd->next = *cp;
-       *cp = cd;
        mutex_unlock(&chrdevs_lock);
        return cd;
 out: