| /* |
| * linux/fs/char_dev.c |
| * |
| * Copyright (C) 1991, 1992 Linus Torvalds |
| */ |
| |
| #include <linux/init.h> |
| #include <linux/fs.h> |
| #include <linux/kdev_t.h> |
| #include <linux/slab.h> |
| #include <linux/string.h> |
| |
| #include <linux/major.h> |
| #include <linux/errno.h> |
| #include <linux/module.h> |
| #include <linux/seq_file.h> |
| |
| #include <linux/kobject.h> |
| #include <linux/kobj_map.h> |
| #include <linux/cdev.h> |
| #include <linux/mutex.h> |
| #include <linux/backing-dev.h> |
| #include <linux/tty.h> |
| |
| #include "internal.h" |
| |
| /* |
| * capabilities for /dev/mem, /dev/kmem and similar directly mappable character |
| * devices |
| * - permits shared-mmap for read, write and/or exec |
| * - does not permit private mmap in NOMMU mode (can't do COW) |
| * - no readahead or I/O queue unplugging required |
| */ |
| struct backing_dev_info directly_mappable_cdev_bdi = { |
| .name = "char", |
| .capabilities = ( |
| #ifdef CONFIG_MMU |
| /* permit private copies of the data to be taken */ |
| BDI_CAP_MAP_COPY | |
| #endif |
| /* permit direct mmap, for read, write or exec */ |
| BDI_CAP_MAP_DIRECT | |
| BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP | |
| /* no writeback happens */ |
| BDI_CAP_NO_ACCT_AND_WRITEBACK), |
| }; |
| |
| static struct kobj_map *cdev_map; |
| |
| static DEFINE_MUTEX(chrdevs_lock); |
| |
| static struct char_device_struct { |
| struct char_device_struct *next; |
| unsigned int major; |
| unsigned int baseminor; |
| int minorct; |
| char name[64]; |
| struct cdev *cdev; /* will die */ |
| } *chrdevs[CHRDEV_MAJOR_HASH_SIZE]; |
| |
| /* index in the above */ |
| static inline int major_to_index(unsigned major) |
| { |
| return major % CHRDEV_MAJOR_HASH_SIZE; |
| } |
| |
| #ifdef CONFIG_PROC_FS |
| |
| void chrdev_show(struct seq_file *f, off_t offset) |
| { |
| struct char_device_struct *cd; |
| |
| if (offset < CHRDEV_MAJOR_HASH_SIZE) { |
| mutex_lock(&chrdevs_lock); |
| for (cd = chrdevs[offset]; cd; cd = cd->next) |
| seq_printf(f, "%3d %s\n", cd->major, cd->name); |
| mutex_unlock(&chrdevs_lock); |
| } |
| } |
| |
| #endif /* CONFIG_PROC_FS */ |
| |
| /* |
| * 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 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); |
| |
| mutex_lock(&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; |
| } |
| mutex_unlock(&chrdevs_lock); |
| return cd; |
| } |
| |
| /** |
| * register_chrdev_region() - register a range of device numbers |
| * @from: the first in the desired range of device numbers; must include |
| * the major number. |
| * @count: the number of consecutive device numbers required |
| * @name: the name of the device or driver. |
| * |
| * Return value is zero on success, a negative error code on failure. |
| */ |
| 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); |
| } |
| |
| /** |
| * alloc_chrdev_region() - register a range of char device numbers |
| * @dev: output parameter for first assigned number |
| * @baseminor: first of the requested range of minor numbers |
| * @count: the number of minor numbers required |
| * @name: the name of the associated device or driver |
| * |
| * Allocates a range of char device numbers. The major number will be |
| * chosen dynamically, and returned (along with the first minor number) |
| * in @dev. Returns zero or a negative error code. |
| */ |
| 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; |
| } |
| |
| /** |
| * __register_chrdev() - create and register a cdev occupying a range of minors |
| * @major: major device number or 0 for dynamic allocation |
| * @baseminor: first of the requested range of minor numbers |
| * @count: the number of minor numbers required |
| * @name: name of this range of devices |
| * @fops: file operations associated with this devices |
| * |
| * If @major == 0 this functions will dynamically allocate a major and return |
| * its number. |
| * |
| * If @major > 0 this function will attempt to reserve a device with the given |
| * major number and will return zero on success. |
| * |
| * Returns a -ve errno on failure. |
| * |
| * The name of this device has nothing to do with the name of the device in |
| * /dev. It only helps to keep track of the different owners of devices. If |
| * your module name has only one type of devices it's ok to use e.g. the name |
| * of the module here. |
| */ |
| int __register_chrdev(unsigned int major, unsigned int baseminor, |
| unsigned int count, const char *name, |
| const struct file_operations *fops) |
| { |
| struct char_device_struct *cd; |
| struct cdev *cdev; |
| int err = -ENOMEM; |
| |
| cd = __register_chrdev_region(major, baseminor, count, 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); |
| |
| err = cdev_add(cdev, MKDEV(cd->major, baseminor), count); |
| if (err) |
| goto out; |
| |
| cd->cdev = cdev; |
| |
| return major ? 0 : cd->major; |
| out: |
| kobject_put(&cdev->kobj); |
| out2: |
| kfree(__unregister_chrdev_region(cd->major, baseminor, count)); |
| return err; |
| } |
| |
| /** |
| * unregister_chrdev_region() - return a range of device numbers |
| * @from: the first in the range of numbers to unregister |
| * @count: the number of device numbers to unregister |
| * |
| * This function will unregister a range of @count device numbers, |
| * starting with @from. The caller should normally be the one who |
| * allocated those numbers in the first place... |
| */ |
| 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)); |
| } |
| } |
| |
| /** |
| * __unregister_chrdev - unregister and destroy a cdev |
| * @major: major device number |
| * @baseminor: first of the range of minor numbers |
| * @count: the number of minor numbers this cdev is occupying |
| * @name: name of this range of devices |
| * |
| * Unregister and destroy the cdev occupying the region described by |
| * @major, @baseminor and @count. This function undoes what |
| * __register_chrdev() did. |
| */ |
| void __unregister_chrdev(unsigned int major, unsigned int baseminor, |
| unsigned int count, const char *name) |
| { |
| struct char_device_struct *cd; |
| |
| cd = __unregister_chrdev_region(major, baseminor, count); |
| if (cd && cd->cdev) |
| cdev_del(cd->cdev); |
| kfree(cd); |
| } |
| |
| 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) { |
| struct module *owner = p->owner; |
| kobject_put(&p->kobj); |
| module_put(owner); |
| } |
| } |
| |
| /* |
| * Called every time a character special file is opened |
| */ |
| static 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); |
| /* Check i_cdev again in case somebody beat us to it while |
| we dropped the lock. */ |
| p = inode->i_cdev; |
| if (!p) { |
| inode->i_cdev = p = new; |
| 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; |
| |
| ret = -ENXIO; |
| filp->f_op = fops_get(p->ops); |
| if (!filp->f_op) |
| goto out_cdev_put; |
| |
| if (filp->f_op->open) { |
| ret = filp->f_op->open(inode, filp); |
| if (ret) |
| goto out_cdev_put; |
| } |
| |
| return 0; |
| |
| out_cdev_put: |
| 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... |
| */ |
| const struct file_operations def_chr_fops = { |
| .open = chrdev_open, |
| .llseek = noop_llseek, |
| }; |
| |
| 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; |
| } |
| |
| /** |
| * cdev_add() - add a char device to the system |
| * @p: the cdev structure for the device |
| * @dev: the first device number for which this device is responsible |
| * @count: the number of consecutive minor numbers corresponding to this |
| * device |
| * |
| * cdev_add() adds the device represented by @p to the system, making it |
| * live immediately. A negative error code is returned on failure. |
| */ |
| int cdev_add(struct cdev *p, dev_t dev, unsigned count) |
| { |
| int error; |
| |
| p->dev = dev; |
| p->count = count; |
| |
| error = kobj_map(cdev_map, dev, count, NULL, |
| exact_match, exact_lock, p); |
| if (error) |
| return error; |
| |
| kobject_get(p->kobj.parent); |
| |
| return 0; |
| } |
| |
| static void cdev_unmap(dev_t dev, unsigned count) |
| { |
| kobj_unmap(cdev_map, dev, count); |
| } |
| |
| /** |
| * cdev_del() - remove a cdev from the system |
| * @p: the cdev structure to be removed |
| * |
| * cdev_del() removes @p from the system, possibly freeing the structure |
| * itself. |
| */ |
| 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); |
| struct kobject *parent = kobj->parent; |
| |
| cdev_purge(p); |
| kobject_put(parent); |
| } |
| |
| static void cdev_dynamic_release(struct kobject *kobj) |
| { |
| struct cdev *p = container_of(kobj, struct cdev, kobj); |
| struct kobject *parent = kobj->parent; |
| |
| cdev_purge(p); |
| kfree(p); |
| kobject_put(parent); |
| } |
| |
| static struct kobj_type ktype_cdev_default = { |
| .release = cdev_default_release, |
| }; |
| |
| static struct kobj_type ktype_cdev_dynamic = { |
| .release = cdev_dynamic_release, |
| }; |
| |
| /** |
| * cdev_alloc() - allocate a cdev structure |
| * |
| * Allocates and returns a cdev structure, or NULL on failure. |
| */ |
| struct cdev *cdev_alloc(void) |
| { |
| struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL); |
| if (p) { |
| INIT_LIST_HEAD(&p->list); |
| kobject_init(&p->kobj, &ktype_cdev_dynamic); |
| } |
| return p; |
| } |
| |
| /** |
| * cdev_init() - initialize a cdev structure |
| * @cdev: the structure to initialize |
| * @fops: the file_operations for this device |
| * |
| * Initializes @cdev, remembering @fops, making it ready to add to the |
| * system with cdev_add(). |
| */ |
| void cdev_init(struct cdev *cdev, const struct file_operations *fops) |
| { |
| memset(cdev, 0, sizeof *cdev); |
| INIT_LIST_HEAD(&cdev->list); |
| kobject_init(&cdev->kobj, &ktype_cdev_default); |
| 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); |
| if (bdi_init(&directly_mappable_cdev_bdi)) |
| panic("Failed to init directly mappable cdev bdi"); |
| } |
| |
| |
| /* 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); |
| EXPORT_SYMBOL(directly_mappable_cdev_bdi); |