char_dev.c 13.1 KB
Newer Older
L
Linus Torvalds 已提交
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
/*
 *  linux/fs/char_dev.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

#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>
16
#include <linux/seq_file.h>
L
Linus Torvalds 已提交
17 18 19 20

#include <linux/kobject.h>
#include <linux/kobj_map.h>
#include <linux/cdev.h>
21
#include <linux/mutex.h>
22
#include <linux/backing-dev.h>
L
Linus Torvalds 已提交
23 24 25 26

#ifdef CONFIG_KMOD
#include <linux/kmod.h>
#endif
27
#include "internal.h"
L
Linus Torvalds 已提交
28

29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46
/*
 * 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 = {
	.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),
};

L
Linus Torvalds 已提交
47 48
static struct kobj_map *cdev_map;

49
static DEFINE_MUTEX(chrdevs_lock);
L
Linus Torvalds 已提交
50 51 52 53 54 55

static struct char_device_struct {
	struct char_device_struct *next;
	unsigned int major;
	unsigned int baseminor;
	int minorct;
56
	char name[64];
L
Linus Torvalds 已提交
57 58
	struct file_operations *fops;
	struct cdev *cdev;		/* will die */
59
} *chrdevs[CHRDEV_MAJOR_HASH_SIZE];
L
Linus Torvalds 已提交
60 61 62 63

/* index in the above */
static inline int major_to_index(int major)
{
64
	return major % CHRDEV_MAJOR_HASH_SIZE;
65 66
}

67
#ifdef CONFIG_PROC_FS
68

69
void chrdev_show(struct seq_file *f, off_t offset)
70 71 72
{
	struct char_device_struct *cd;

73 74 75 76 77
	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);
L
Linus Torvalds 已提交
78
	}
79 80
}

81
#endif /* CONFIG_PROC_FS */
L
Linus Torvalds 已提交
82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101

/*
 * 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;

102
	cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);
L
Linus Torvalds 已提交
103 104 105
	if (cd == NULL)
		return ERR_PTR(-ENOMEM);

106
	mutex_lock(&chrdevs_lock);
L
Linus Torvalds 已提交
107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125

	/* 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;
126
	strncpy(cd->name,name, 64);
L
Linus Torvalds 已提交
127 128 129 130 131

	i = major_to_index(major);

	for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
		if ((*cp)->major > major ||
132 133 134
		    ((*cp)->major == major &&
		     (((*cp)->baseminor >= baseminor) ||
		      ((*cp)->baseminor + (*cp)->minorct > baseminor))))
L
Linus Torvalds 已提交
135
			break;
136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154

	/* 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;
		}
L
Linus Torvalds 已提交
155
	}
156

L
Linus Torvalds 已提交
157 158
	cd->next = *cp;
	*cp = cd;
159
	mutex_unlock(&chrdevs_lock);
L
Linus Torvalds 已提交
160 161
	return cd;
out:
162
	mutex_unlock(&chrdevs_lock);
L
Linus Torvalds 已提交
163 164 165 166 167 168 169 170 171 172
	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);

173
	mutex_lock(&chrdevs_lock);
L
Linus Torvalds 已提交
174 175 176 177 178 179 180 181 182
	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;
	}
183
	mutex_unlock(&chrdevs_lock);
L
Linus Torvalds 已提交
184 185 186
	return cd;
}

J
Jonathan Corbet 已提交
187 188 189 190 191 192 193 194 195
/**
 * 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.
 */
L
Linus Torvalds 已提交
196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220
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);
}

J
Jonathan Corbet 已提交
221 222 223 224 225 226 227 228 229 230 231
/**
 * 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.
 */
L
Linus Torvalds 已提交
232 233 234 235 236 237 238 239 240 241 242
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;
}

243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264
/**
 * register_chrdev() - Register a major number for character devices.
 * @major: major device number or 0 for dynamic allocation
 * @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.
 *
 * This function registers a range of 256 minor numbers. The first minor number
 * is 0.
 */
L
Linus Torvalds 已提交
265
int register_chrdev(unsigned int major, const char *name,
266
		    const struct file_operations *fops)
L
Linus Torvalds 已提交
267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300
{
	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;
}

J
Jonathan Corbet 已提交
301 302 303 304 305 306 307 308 309
/**
 * 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...
 */
L
Linus Torvalds 已提交
310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350
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) {
B
Brian King 已提交
351
		struct module *owner = p->owner;
L
Linus Torvalds 已提交
352
		kobject_put(&p->kobj);
B
Brian King 已提交
353
		module_put(owner);
L
Linus Torvalds 已提交
354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413
	}
}

/*
 * 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);
}

A
Adrian Bunk 已提交
414
static void cdev_purge(struct cdev *cdev)
L
Linus Torvalds 已提交
415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430
{
	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...
 */
431
const struct file_operations def_chr_fops = {
L
Linus Torvalds 已提交
432 433 434 435 436 437 438 439 440 441 442 443 444 445 446
	.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;
}

J
Jonathan Corbet 已提交
447 448 449 450 451 452 453 454 455 456
/**
 * 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.
 */
L
Linus Torvalds 已提交
457 458 459 460 461 462 463 464 465 466 467 468
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);
}

J
Jonathan Corbet 已提交
469 470 471 472 473 474 475
/**
 * 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.
 */
L
Linus Torvalds 已提交
476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503
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,
};

J
Jonathan Corbet 已提交
504 505 506 507 508
/**
 * cdev_alloc() - allocate a cdev structure
 *
 * Allocates and returns a cdev structure, or NULL on failure.
 */
L
Linus Torvalds 已提交
509 510
struct cdev *cdev_alloc(void)
{
511
	struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);
L
Linus Torvalds 已提交
512 513 514 515 516 517 518 519
	if (p) {
		p->kobj.ktype = &ktype_cdev_dynamic;
		INIT_LIST_HEAD(&p->list);
		kobject_init(&p->kobj);
	}
	return p;
}

J
Jonathan Corbet 已提交
520 521 522 523 524 525 526 527
/**
 * 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().
 */
528
void cdev_init(struct cdev *cdev, const struct file_operations *fops)
L
Linus Torvalds 已提交
529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560
{
	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);
561
EXPORT_SYMBOL(directly_mappable_cdev_bdi);