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[PATCH] cdev documentation

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Add some documentation comments for the cdev interface.

Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Cc: Rolf Eike Beer <eike-kernel@sf-tec.de>
Acked-by: "Randy.Dunlap" <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Jonathan Corbet 2006-09-29 02:00:44 -07:00 committed by Linus Torvalds
parent 5785c95bae
commit cf3e43dbe0
2 changed files with 64 additions and 0 deletions
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5
Documentation/DocBook/kernel-api.tmpl
View File

@ -454,6 +454,11 @@ X!Edrivers/pnp/system.c
!Eblock/ll_rw_blk.c
</chapter>
<chapter id="chrdev">
<title>Char devices</title>
!Efs/char_dev.c
</chapter>
<chapter id="miscdev">
<title>Miscellaneous Devices</title>
!Edrivers/char/misc.c

59
fs/char_dev.c
View File

@ -183,6 +183,15 @@ __unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
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;
@ -208,6 +217,17 @@ fail:
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)
{
@ -277,6 +297,15 @@ out2:
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;
@ -414,6 +443,16 @@ static int exact_lock(dev_t dev, void *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;
@ -426,6 +465,13 @@ 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);
@ -454,6 +500,11 @@ 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);
@ -465,6 +516,14 @@ struct cdev *cdev_alloc(void)
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);