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Subject[PATCH v3 3/4] chardev: code cleanup for __register_chrdev_region()
Date
It's just code cleanup, not functional change.

Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
---
v1->v2:
- Split fix and cleanup patches.
- Remove printing minor range in chrdev_show().

v2->v3:
- Set variable ret to '-EBUSY' before checking minor range overlap.

fs/char_dev.c | 70 +++++++++++++++++++++------------------------------
1 file changed, 29 insertions(+), 41 deletions(-)

diff --git a/fs/char_dev.c b/fs/char_dev.c
index 6803e98414f1..47fd0561b03d 100644
--- 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;
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 +132,37 @@ __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));
-
+ ret = -EBUSY;
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:
--
2.20.1
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