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本帖最后由 chishanmingshen 于 2014-03-12 14:46 编辑
from 3.7- 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;
- int i;
- cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);
- if (cd == NULL)
- return ERR_PTR(-ENOMEM);
- mutex_lock(&chrdevs_lock);
- /* temporary */
- if (major == 0) {
- for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
- if (chrdevs[i] == NULL)<----------
- break;<--------------------------此2行为何不是检查是否主次设备号的范围是否重叠?
- }
- if (i == 0) {
- ret = -EBUSY;
- goto out;
- }
- major = i;
- ret = major;
- }
- cd->major = major;
- cd->baseminor = baseminor;
- cd->minorct = minorct;
- strlcpy(cd->name, name, sizeof(cd->name));
- i = major_to_index(major);
- for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
- if ((*cp)->major > major ||
- ((*cp)->major == major &&
- (((*cp)->baseminor >= baseminor) ||
- ((*cp)->baseminor + (*cp)->minorct > baseminor))))
- 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;
- /* New driver overlaps from the left. */
- if (new_max >= old_min && new_max <= old_max) {
- ret = -EBUSY;
- goto out;
- }
- /* New driver overlaps from the right. */
- if (new_min <= old_max && new_min >= old_min) {
- ret = -EBUSY;
- goto out;
- }
- }
- cd->next = *cp;
- *cp = cd;
- mutex_unlock(&chrdevs_lock);
- return cd;
- out:
- mutex_unlock(&chrdevs_lock);
- kfree(cd);
- return ERR_PTR(ret);
- }
复制代码 求指点,谢谢! |
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