/* * linux/fs/char_dev.c * * Copyright (C) 1991, 1992 Linus Torvalds */ #include <linux/config.h> #include <linux/init.h> #include <linux/fs.h> #include <linux/slab.h> #include <linux/string.h> #include <linux/major.h> #include <linux/errno.h> #include <linux/module.h> #include <linux/smp_lock.h> #include <linux/devfs_fs_kernel.h> #include <linux/kobject.h> #include <linux/kobj_map.h> #include <linux/cdev.h> #ifdef CONFIG_KMOD #include <linux/kmod.h> #endif static struct kobj_map *cdev_map; #define MAX_PROBE_HASH 255 /* random */ static DECLARE_MUTEX(chrdevs_lock); static struct char_device_struct { struct char_device_struct *next; unsigned int major; unsigned int baseminor; int minorct; const char *name; struct file_operations *fops; struct cdev *cdev; /* will die */ } *chrdevs[MAX_PROBE_HASH]; /* index in the above */ static inline int major_to_index(int major) { return major % MAX_PROBE_HASH; } /* get char device names in somewhat random order */ int get_chrdev_list(char *page) { struct char_device_struct *cd; int i, len; len = sprintf(page, "Character devices:\n"); down(&chrdevs_lock); for (i = 0; i < ARRAY_SIZE(chrdevs) ; i++) { for (cd = chrdevs[i]; cd; cd = cd->next) { /* * if the current name, plus the 5 extra characters * in the device line for this entry * would run us off the page, we're done */ if ((len+strlen(cd->name) + 5) >= PAGE_SIZE) goto page_full; len += sprintf(page+len, "%3d %s\n", cd->major, cd->name); } } page_full: up(&chrdevs_lock); return len; } /* * 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 = kmalloc(sizeof(struct char_device_struct), GFP_KERNEL); if (cd == NULL) return ERR_PTR(-ENOMEM); memset(cd, 0, sizeof(struct char_device_struct)); down(&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; cd->name = name; i = major_to_index(major); for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next) if ((*cp)->major > major || ((*cp)->major == major && (*cp)->baseminor >= baseminor)) break; if (*cp && (*cp)->major == major && (*cp)->baseminor < baseminor + minorct) { ret = -EBUSY; goto out; } cd->next = *cp; *cp = cd; up(&chrdevs_lock); return cd; out: up(&chrdevs_lock); kfree(cd); return ERR_PTR(ret); } static struct char_device_struct * __unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct) { struct char_device_struct *cd = NULL, **cp; int i = major_to_index(major); up(&chrdevs_lock); for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next) if ((*cp)->major == major && (*cp)->baseminor == baseminor && (*cp)->minorct == minorct) break; if (*cp) { cd = *cp; *cp = cd->next; } up(&chrdevs_lock); return cd; } int register_chrdev_region(dev_t from, unsigned count, const char *name) { struct char_device_struct *cd; dev_t to = from + count; dev_t n, next; for (n = from; n < to; n = next) { next = MKDEV(MAJOR(n)+1, 0); if (next > to) next = to; cd = __register_chrdev_region(MAJOR(n), MINOR(n), next - n, name); if (IS_ERR(cd)) goto fail; } return 0; fail: to = n; for (n = from; n < to; n = next) { next = MKDEV(MAJOR(n)+1, 0); kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n)); } return PTR_ERR(cd); } int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count, const char *name) { struct char_device_struct *cd; cd = __register_chrdev_region(0, baseminor, count, name); if (IS_ERR(cd)) return PTR_ERR(cd); *dev = MKDEV(cd->major, cd->baseminor); return 0; } int register_chrdev(unsigned int major, const char *name, struct file_operations *fops) { struct char_device_struct *cd; struct cdev *cdev; char *s; int err = -ENOMEM; cd = __register_chrdev_region(major, 0, 256, name); if (IS_ERR(cd)) return PTR_ERR(cd); cdev = cdev_alloc(); if (!cdev) goto out2; cdev->owner = fops->owner; cdev->ops = fops; kobject_set_name(&cdev->kobj, "%s", name); for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/')) *s = '!'; err = cdev_add(cdev, MKDEV(cd->major, 0), 256); if (err) goto out; cd->cdev = cdev; return major ? 0 : cd->major; out: kobject_put(&cdev->kobj); out2: kfree(__unregister_chrdev_region(cd->major, 0, 256)); return err; } void unregister_chrdev_region(dev_t from, unsigned count) { dev_t to = from + count; dev_t n, next; for (n = from; n < to; n = next) { next = MKDEV(MAJOR(n)+1, 0); if (next > to) next = to; kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n)); } } int unregister_chrdev(unsigned int major, const char *name) { struct char_device_struct *cd; cd = __unregister_chrdev_region(major, 0, 256); if (cd && cd->cdev) cdev_del(cd->cdev); kfree(cd); return 0; } static DEFINE_SPINLOCK(cdev_lock); static struct kobject *cdev_get(struct cdev *p) { struct module *owner = p->owner; struct kobject *kobj; if (owner && !try_module_get(owner)) return NULL; kobj = kobject_get(&p->kobj); if (!kobj) module_put(owner); return kobj; } void cdev_put(struct cdev *p) { if (p) { kobject_put(&p->kobj); module_put(p->owner); } } /* * Called every time a character special file is opened */ int chrdev_open(struct inode * inode, struct file * filp) { struct cdev *p; struct cdev *new = NULL; int ret = 0; spin_lock(&cdev_lock); p = inode->i_cdev; if (!p) { struct kobject *kobj; int idx; spin_unlock(&cdev_lock); kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx); if (!kobj) return -ENXIO; new = container_of(kobj, struct cdev, kobj); spin_lock(&cdev_lock); p = inode->i_cdev; if (!p) { inode->i_cdev = p = new; inode->i_cindex = idx; list_add(&inode->i_devices, &p->list); new = NULL; } else if (!cdev_get(p)) ret = -ENXIO; } else if (!cdev_get(p)) ret = -ENXIO; spin_unlock(&cdev_lock); cdev_put(new); if (ret) return ret; filp->f_op = fops_get(p->ops); if (!filp->f_op) { cdev_put(p); return -ENXIO; } if (filp->f_op->open) { lock_kernel(); ret = filp->f_op->open(inode,filp); unlock_kernel(); } if (ret) cdev_put(p); return ret; } void cd_forget(struct inode *inode) { spin_lock(&cdev_lock); list_del_init(&inode->i_devices); inode->i_cdev = NULL; spin_unlock(&cdev_lock); } static void cdev_purge(struct cdev *cdev) { spin_lock(&cdev_lock); while (!list_empty(&cdev->list)) { struct inode *inode; inode = container_of(cdev->list.next, struct inode, i_devices); list_del_init(&inode->i_devices); inode->i_cdev = NULL; } spin_unlock(&cdev_lock); } /* * Dummy default file-operations: the only thing this does * is contain the open that then fills in the correct operations * depending on the special file... */ struct file_operations def_chr_fops = { .open = chrdev_open, }; static struct kobject *exact_match(dev_t dev, int *part, void *data) { struct cdev *p = data; return &p->kobj; } static int exact_lock(dev_t dev, void *data) { struct cdev *p = data; return cdev_get(p) ? 0 : -1; } int cdev_add(struct cdev *p, dev_t dev, unsigned count) { p->dev = dev; p->count = count; return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p); } static void cdev_unmap(dev_t dev, unsigned count) { kobj_unmap(cdev_map, dev, count); } void cdev_del(struct cdev *p) { cdev_unmap(p->dev, p->count); kobject_put(&p->kobj); } static void cdev_default_release(struct kobject *kobj) { struct cdev *p = container_of(kobj, struct cdev, kobj); cdev_purge(p); } static void cdev_dynamic_release(struct kobject *kobj) { struct cdev *p = container_of(kobj, struct cdev, kobj); cdev_purge(p); kfree(p); } static struct kobj_type ktype_cdev_default = { .release = cdev_default_release, }; static struct kobj_type ktype_cdev_dynamic = { .release = cdev_dynamic_release, }; struct cdev *cdev_alloc(void) { struct cdev *p = kmalloc(sizeof(struct cdev), GFP_KERNEL); if (p) { memset(p, 0, sizeof(struct cdev)); p->kobj.ktype = &ktype_cdev_dynamic; INIT_LIST_HEAD(&p->list); kobject_init(&p->kobj); } return p; } void cdev_init(struct cdev *cdev, struct file_operations *fops) { memset(cdev, 0, sizeof *cdev); INIT_LIST_HEAD(&cdev->list); cdev->kobj.ktype = &ktype_cdev_default; kobject_init(&cdev->kobj); cdev->ops = fops; } static struct kobject *base_probe(dev_t dev, int *part, void *data) { if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0) /* Make old-style 2.4 aliases work */ request_module("char-major-%d", MAJOR(dev)); return NULL; } void __init chrdev_init(void) { cdev_map = kobj_map_init(base_probe, &chrdevs_lock); } /* Let modules do char dev stuff */ EXPORT_SYMBOL(register_chrdev_region); EXPORT_SYMBOL(unregister_chrdev_region); EXPORT_SYMBOL(alloc_chrdev_region); EXPORT_SYMBOL(cdev_init); EXPORT_SYMBOL(cdev_alloc); EXPORT_SYMBOL(cdev_del); EXPORT_SYMBOL(cdev_add); EXPORT_SYMBOL(register_chrdev); EXPORT_SYMBOL(unregister_chrdev);