/* * Register a single major with a specified minor range. * * If major == 0 this functions will dynamically allocate a major and return * its number. * * If major > 0 this function will attempt to reserve the passed range of * minors and will return zero on success. * * Returns a -ve errno on failure. */ 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; } 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); }
static inline int dev_to_index(dev_t dev) { return major_to_index(MAJOR(dev)); }