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author | root <root@artemis.panaceas.org> | 2015-12-25 04:40:36 +0000 |
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committer | root <root@artemis.panaceas.org> | 2015-12-25 04:40:36 +0000 |
commit | 849369d6c66d3054688672f97d31fceb8e8230fb (patch) | |
tree | 6135abc790ca67dedbe07c39806591e70eda81ce /fs/char_dev.c | |
download | linux-3.0.35-kobo-849369d6c66d3054688672f97d31fceb8e8230fb.tar.gz linux-3.0.35-kobo-849369d6c66d3054688672f97d31fceb8e8230fb.tar.bz2 linux-3.0.35-kobo-849369d6c66d3054688672f97d31fceb8e8230fb.zip |
initial_commit
Diffstat (limited to 'fs/char_dev.c')
-rw-r--r-- | fs/char_dev.c | 575 |
1 files changed, 575 insertions, 0 deletions
diff --git a/fs/char_dev.c b/fs/char_dev.c new file mode 100644 index 00000000..dca9e5e0 --- /dev/null +++ b/fs/char_dev.c @@ -0,0 +1,575 @@ +/* + * 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) +{ + 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); +} + +/** + * 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); + 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, +}; + +/** + * 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); + bdi_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); |