1 // SPDX-License-Identifier: GPL-2.0-or-later
3 i2c-dev.c - i2c-bus driver, char device interface
5 Copyright (C) 1995-97 Simon G. Vogl
6 Copyright (C) 1998-99 Frodo Looijaard <frodol@dds.nl>
7 Copyright (C) 2003 Greg Kroah-Hartman <greg@kroah.com>
11 /* Note that this is a complete rewrite of Simon Vogl's i2c-dev module.
12 But I have used so much of his original code and ideas that it seems
13 only fair to recognize him as co-author -- Frodo */
15 /* The I2C_RDWR ioctl code is written by Kolja Waschk <waschk@telos.de> */
17 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
19 #include <linux/cdev.h>
20 #include <linux/compat.h>
21 #include <linux/device.h>
23 #include <linux/i2c-dev.h>
24 #include <linux/i2c.h>
25 #include <linux/init.h>
26 #include <linux/jiffies.h>
27 #include <linux/kernel.h>
28 #include <linux/list.h>
29 #include <linux/module.h>
30 #include <linux/notifier.h>
31 #include <linux/slab.h>
32 #include <linux/uaccess.h>
35 * An i2c_dev represents an i2c_adapter ... an I2C or SMBus master, not a
36 * slave (i2c_client) with which messages will be exchanged. It's coupled
37 * with a character special file which is accessed by user mode drivers.
39 * The list of i2c_dev structures is parallel to the i2c_adapter lists
40 * maintained by the driver model, and is updated using bus notifications.
43 struct list_head list;
44 struct i2c_adapter *adap;
49 #define I2C_MINORS (MINORMASK + 1)
50 static LIST_HEAD(i2c_dev_list);
51 static DEFINE_SPINLOCK(i2c_dev_list_lock);
53 static struct i2c_dev *i2c_dev_get_by_minor(unsigned index)
55 struct i2c_dev *i2c_dev;
57 spin_lock(&i2c_dev_list_lock);
58 list_for_each_entry(i2c_dev, &i2c_dev_list, list) {
59 if (i2c_dev->adap->nr == index)
64 spin_unlock(&i2c_dev_list_lock);
68 static struct i2c_dev *get_free_i2c_dev(struct i2c_adapter *adap)
70 struct i2c_dev *i2c_dev;
72 if (adap->nr >= I2C_MINORS) {
73 pr_err("Out of device minors (%d)\n", adap->nr);
74 return ERR_PTR(-ENODEV);
77 i2c_dev = kzalloc(sizeof(*i2c_dev), GFP_KERNEL);
79 return ERR_PTR(-ENOMEM);
82 spin_lock(&i2c_dev_list_lock);
83 list_add_tail(&i2c_dev->list, &i2c_dev_list);
84 spin_unlock(&i2c_dev_list_lock);
88 static void put_i2c_dev(struct i2c_dev *i2c_dev, bool del_cdev)
90 spin_lock(&i2c_dev_list_lock);
91 list_del(&i2c_dev->list);
92 spin_unlock(&i2c_dev_list_lock);
94 cdev_device_del(&i2c_dev->cdev, &i2c_dev->dev);
95 put_device(&i2c_dev->dev);
98 static ssize_t name_show(struct device *dev,
99 struct device_attribute *attr, char *buf)
101 struct i2c_dev *i2c_dev = i2c_dev_get_by_minor(MINOR(dev->devt));
105 return sysfs_emit(buf, "%s\n", i2c_dev->adap->name);
107 static DEVICE_ATTR_RO(name);
109 static struct attribute *i2c_attrs[] = {
113 ATTRIBUTE_GROUPS(i2c);
115 /* ------------------------------------------------------------------------- */
118 * After opening an instance of this character special file, a file
119 * descriptor starts out associated only with an i2c_adapter (and bus).
121 * Using the I2C_RDWR ioctl(), you can then *immediately* issue i2c_msg
122 * traffic to any devices on the bus used by that adapter. That's because
123 * the i2c_msg vectors embed all the addressing information they need, and
124 * are submitted directly to an i2c_adapter. However, SMBus-only adapters
125 * don't support that interface.
127 * To use read()/write() system calls on that file descriptor, or to use
128 * SMBus interfaces (and work with SMBus-only hosts!), you must first issue
129 * an I2C_SLAVE (or I2C_SLAVE_FORCE) ioctl. That configures an anonymous
130 * (never registered) i2c_client so it holds the addressing information
131 * needed by those system calls and by this SMBus interface.
134 static ssize_t i2cdev_read(struct file *file, char __user *buf, size_t count,
140 struct i2c_client *client = file->private_data;
142 /* Adapter must support I2C transfers */
143 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
149 tmp = kzalloc(count, GFP_KERNEL);
153 pr_debug("i2c-%d reading %zu bytes.\n", iminor(file_inode(file)), count);
155 ret = i2c_master_recv(client, tmp, count);
157 if (copy_to_user(buf, tmp, ret))
163 static ssize_t i2cdev_write(struct file *file, const char __user *buf,
164 size_t count, loff_t *offset)
168 struct i2c_client *client = file->private_data;
170 /* Adapter must support I2C transfers */
171 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
177 tmp = memdup_user(buf, count);
181 pr_debug("i2c-%d writing %zu bytes.\n", iminor(file_inode(file)), count);
183 ret = i2c_master_send(client, tmp, count);
188 static int i2cdev_check(struct device *dev, void *addrp)
190 struct i2c_client *client = i2c_verify_client(dev);
192 if (!client || client->addr != *(unsigned int *)addrp)
195 return dev->driver ? -EBUSY : 0;
198 /* walk up mux tree */
199 static int i2cdev_check_mux_parents(struct i2c_adapter *adapter, int addr)
201 struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);
204 result = device_for_each_child(&adapter->dev, &addr, i2cdev_check);
205 if (!result && parent)
206 result = i2cdev_check_mux_parents(parent, addr);
211 /* recurse down mux tree */
212 static int i2cdev_check_mux_children(struct device *dev, void *addrp)
216 if (dev->type == &i2c_adapter_type)
217 result = device_for_each_child(dev, addrp,
218 i2cdev_check_mux_children);
220 result = i2cdev_check(dev, addrp);
225 /* This address checking function differs from the one in i2c-core
226 in that it considers an address with a registered device, but no
227 driver bound to it, as NOT busy. */
228 static int i2cdev_check_addr(struct i2c_adapter *adapter, unsigned int addr)
230 struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);
234 result = i2cdev_check_mux_parents(parent, addr);
237 result = device_for_each_child(&adapter->dev, &addr,
238 i2cdev_check_mux_children);
243 static noinline int i2cdev_ioctl_rdwr(struct i2c_client *client,
244 unsigned nmsgs, struct i2c_msg *msgs)
246 u8 __user **data_ptrs;
249 /* Adapter must support I2C transfers */
250 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
253 data_ptrs = kmalloc_array(nmsgs, sizeof(u8 __user *), GFP_KERNEL);
254 if (data_ptrs == NULL) {
260 for (i = 0; i < nmsgs; i++) {
261 /* Limit the size of the message to a sane amount */
262 if (msgs[i].len > 8192) {
267 data_ptrs[i] = (u8 __user *)msgs[i].buf;
268 msgs[i].buf = memdup_user(data_ptrs[i], msgs[i].len);
269 if (IS_ERR(msgs[i].buf)) {
270 res = PTR_ERR(msgs[i].buf);
273 /* memdup_user allocates with GFP_KERNEL, so DMA is ok */
274 msgs[i].flags |= I2C_M_DMA_SAFE;
277 * If the message length is received from the slave (similar
278 * to SMBus block read), we must ensure that the buffer will
279 * be large enough to cope with a message length of
280 * I2C_SMBUS_BLOCK_MAX as this is the maximum underlying bus
281 * drivers allow. The first byte in the buffer must be
282 * pre-filled with the number of extra bytes, which must be
283 * at least one to hold the message length, but can be
284 * greater (for example to account for a checksum byte at
285 * the end of the message.)
287 if (msgs[i].flags & I2C_M_RECV_LEN) {
288 if (!(msgs[i].flags & I2C_M_RD) ||
289 msgs[i].len < 1 || msgs[i].buf[0] < 1 ||
290 msgs[i].len < msgs[i].buf[0] +
291 I2C_SMBUS_BLOCK_MAX) {
297 msgs[i].len = msgs[i].buf[0];
302 for (j = 0; j < i; ++j)
309 res = i2c_transfer(client->adapter, msgs, nmsgs);
311 if (res >= 0 && (msgs[i].flags & I2C_M_RD)) {
312 if (copy_to_user(data_ptrs[i], msgs[i].buf,
323 static noinline int i2cdev_ioctl_smbus(struct i2c_client *client,
324 u8 read_write, u8 command, u32 size,
325 union i2c_smbus_data __user *data)
327 union i2c_smbus_data temp = {};
330 if ((size != I2C_SMBUS_BYTE) &&
331 (size != I2C_SMBUS_QUICK) &&
332 (size != I2C_SMBUS_BYTE_DATA) &&
333 (size != I2C_SMBUS_WORD_DATA) &&
334 (size != I2C_SMBUS_PROC_CALL) &&
335 (size != I2C_SMBUS_BLOCK_DATA) &&
336 (size != I2C_SMBUS_I2C_BLOCK_BROKEN) &&
337 (size != I2C_SMBUS_I2C_BLOCK_DATA) &&
338 (size != I2C_SMBUS_BLOCK_PROC_CALL)) {
339 dev_dbg(&client->adapter->dev,
340 "size out of range (%x) in ioctl I2C_SMBUS.\n",
344 /* Note that I2C_SMBUS_READ and I2C_SMBUS_WRITE are 0 and 1,
345 so the check is valid if size==I2C_SMBUS_QUICK too. */
346 if ((read_write != I2C_SMBUS_READ) &&
347 (read_write != I2C_SMBUS_WRITE)) {
348 dev_dbg(&client->adapter->dev,
349 "read_write out of range (%x) in ioctl I2C_SMBUS.\n",
354 /* Note that command values are always valid! */
356 if ((size == I2C_SMBUS_QUICK) ||
357 ((size == I2C_SMBUS_BYTE) &&
358 (read_write == I2C_SMBUS_WRITE)))
359 /* These are special: we do not use data */
360 return i2c_smbus_xfer(client->adapter, client->addr,
361 client->flags, read_write,
362 command, size, NULL);
365 dev_dbg(&client->adapter->dev,
366 "data is NULL pointer in ioctl I2C_SMBUS.\n");
370 if ((size == I2C_SMBUS_BYTE_DATA) ||
371 (size == I2C_SMBUS_BYTE))
372 datasize = sizeof(data->byte);
373 else if ((size == I2C_SMBUS_WORD_DATA) ||
374 (size == I2C_SMBUS_PROC_CALL))
375 datasize = sizeof(data->word);
376 else /* size == smbus block, i2c block, or block proc. call */
377 datasize = sizeof(data->block);
379 if ((size == I2C_SMBUS_PROC_CALL) ||
380 (size == I2C_SMBUS_BLOCK_PROC_CALL) ||
381 (size == I2C_SMBUS_I2C_BLOCK_DATA) ||
382 (read_write == I2C_SMBUS_WRITE)) {
383 if (copy_from_user(&temp, data, datasize))
386 if (size == I2C_SMBUS_I2C_BLOCK_BROKEN) {
387 /* Convert old I2C block commands to the new
388 convention. This preserves binary compatibility. */
389 size = I2C_SMBUS_I2C_BLOCK_DATA;
390 if (read_write == I2C_SMBUS_READ)
391 temp.block[0] = I2C_SMBUS_BLOCK_MAX;
393 res = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
394 read_write, command, size, &temp);
395 if (!res && ((size == I2C_SMBUS_PROC_CALL) ||
396 (size == I2C_SMBUS_BLOCK_PROC_CALL) ||
397 (read_write == I2C_SMBUS_READ))) {
398 if (copy_to_user(data, &temp, datasize))
404 static long i2cdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
406 struct i2c_client *client = file->private_data;
409 dev_dbg(&client->adapter->dev, "ioctl, cmd=0x%02x, arg=0x%02lx\n",
414 case I2C_SLAVE_FORCE:
416 (((client->flags & I2C_M_TEN) == 0) && arg > 0x7f))
418 if (cmd == I2C_SLAVE && i2cdev_check_addr(client->adapter, arg))
420 /* REVISIT: address could become busy later */
425 client->flags |= I2C_M_TEN;
427 client->flags &= ~I2C_M_TEN;
431 * Setting the PEC flag here won't affect kernel drivers,
432 * which will be using the i2c_client node registered with
433 * the driver model core. Likewise, when that client has
434 * the PEC flag already set, the i2c-dev driver won't see
435 * (or use) this setting.
438 client->flags |= I2C_CLIENT_PEC;
440 client->flags &= ~I2C_CLIENT_PEC;
443 funcs = i2c_get_functionality(client->adapter);
444 return put_user(funcs, (unsigned long __user *)arg);
447 struct i2c_rdwr_ioctl_data rdwr_arg;
448 struct i2c_msg *rdwr_pa;
450 if (copy_from_user(&rdwr_arg,
451 (struct i2c_rdwr_ioctl_data __user *)arg,
455 if (!rdwr_arg.msgs || rdwr_arg.nmsgs == 0)
459 * Put an arbitrary limit on the number of messages that can
462 if (rdwr_arg.nmsgs > I2C_RDWR_IOCTL_MAX_MSGS)
465 rdwr_pa = memdup_array_user(rdwr_arg.msgs,
466 rdwr_arg.nmsgs, sizeof(struct i2c_msg));
468 return PTR_ERR(rdwr_pa);
470 return i2cdev_ioctl_rdwr(client, rdwr_arg.nmsgs, rdwr_pa);
474 struct i2c_smbus_ioctl_data data_arg;
475 if (copy_from_user(&data_arg,
476 (struct i2c_smbus_ioctl_data __user *) arg,
477 sizeof(struct i2c_smbus_ioctl_data)))
479 return i2cdev_ioctl_smbus(client, data_arg.read_write,
488 client->adapter->retries = arg;
494 /* For historical reasons, user-space sets the timeout
495 * value in units of 10 ms.
497 client->adapter->timeout = msecs_to_jiffies(arg * 10);
500 /* NOTE: returning a fault code here could cause trouble
501 * in buggy userspace code. Some old kernel bugs returned
502 * zero in this case, and userspace code might accidentally
503 * have depended on that bug.
512 struct i2c_smbus_ioctl_data32 {
516 compat_caddr_t data; /* union i2c_smbus_data *data */
526 struct i2c_rdwr_ioctl_data32 {
527 compat_caddr_t msgs; /* struct i2c_msg __user *msgs */
531 static long compat_i2cdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
533 struct i2c_client *client = file->private_data;
537 funcs = i2c_get_functionality(client->adapter);
538 return put_user(funcs, (compat_ulong_t __user *)arg);
540 struct i2c_rdwr_ioctl_data32 rdwr_arg;
541 struct i2c_msg32 __user *p;
542 struct i2c_msg *rdwr_pa;
545 if (copy_from_user(&rdwr_arg,
546 (struct i2c_rdwr_ioctl_data32 __user *)arg,
550 if (!rdwr_arg.msgs || rdwr_arg.nmsgs == 0)
553 if (rdwr_arg.nmsgs > I2C_RDWR_IOCTL_MAX_MSGS)
556 rdwr_pa = kmalloc_array(rdwr_arg.nmsgs, sizeof(struct i2c_msg),
561 p = compat_ptr(rdwr_arg.msgs);
562 for (i = 0; i < rdwr_arg.nmsgs; i++) {
563 struct i2c_msg32 umsg;
564 if (copy_from_user(&umsg, p + i, sizeof(umsg))) {
568 rdwr_pa[i] = (struct i2c_msg) {
572 .buf = (__force __u8 *)compat_ptr(umsg.buf),
576 return i2cdev_ioctl_rdwr(client, rdwr_arg.nmsgs, rdwr_pa);
579 struct i2c_smbus_ioctl_data32 data32;
580 if (copy_from_user(&data32,
584 return i2cdev_ioctl_smbus(client, data32.read_write,
587 compat_ptr(data32.data));
590 return i2cdev_ioctl(file, cmd, arg);
594 #define compat_i2cdev_ioctl NULL
597 static int i2cdev_open(struct inode *inode, struct file *file)
599 unsigned int minor = iminor(inode);
600 struct i2c_client *client;
601 struct i2c_adapter *adap;
603 adap = i2c_get_adapter(minor);
607 /* This creates an anonymous i2c_client, which may later be
608 * pointed to some address using I2C_SLAVE or I2C_SLAVE_FORCE.
610 * This client is ** NEVER REGISTERED ** with the driver model
611 * or I2C core code!! It just holds private copies of addressing
612 * information and maybe a PEC flag.
614 client = kzalloc(sizeof(*client), GFP_KERNEL);
616 i2c_put_adapter(adap);
619 snprintf(client->name, I2C_NAME_SIZE, "i2c-dev %d", adap->nr);
621 client->adapter = adap;
622 file->private_data = client;
627 static int i2cdev_release(struct inode *inode, struct file *file)
629 struct i2c_client *client = file->private_data;
631 i2c_put_adapter(client->adapter);
633 file->private_data = NULL;
638 static const struct file_operations i2cdev_fops = {
639 .owner = THIS_MODULE,
641 .write = i2cdev_write,
642 .unlocked_ioctl = i2cdev_ioctl,
643 .compat_ioctl = compat_i2cdev_ioctl,
645 .release = i2cdev_release,
648 /* ------------------------------------------------------------------------- */
650 static const struct class i2c_dev_class = {
652 .dev_groups = i2c_groups,
655 static void i2cdev_dev_release(struct device *dev)
657 struct i2c_dev *i2c_dev;
659 i2c_dev = container_of(dev, struct i2c_dev, dev);
663 static int i2cdev_attach_adapter(struct device *dev)
665 struct i2c_adapter *adap;
666 struct i2c_dev *i2c_dev;
669 if (dev->type != &i2c_adapter_type)
671 adap = to_i2c_adapter(dev);
673 i2c_dev = get_free_i2c_dev(adap);
677 cdev_init(&i2c_dev->cdev, &i2cdev_fops);
678 i2c_dev->cdev.owner = THIS_MODULE;
680 device_initialize(&i2c_dev->dev);
681 i2c_dev->dev.devt = MKDEV(I2C_MAJOR, adap->nr);
682 i2c_dev->dev.class = &i2c_dev_class;
683 i2c_dev->dev.parent = &adap->dev;
684 i2c_dev->dev.release = i2cdev_dev_release;
686 res = dev_set_name(&i2c_dev->dev, "i2c-%d", adap->nr);
688 goto err_put_i2c_dev;
690 res = cdev_device_add(&i2c_dev->cdev, &i2c_dev->dev);
692 goto err_put_i2c_dev;
694 pr_debug("adapter [%s] registered as minor %d\n", adap->name, adap->nr);
698 put_i2c_dev(i2c_dev, false);
702 static int i2cdev_detach_adapter(struct device *dev)
704 struct i2c_adapter *adap;
705 struct i2c_dev *i2c_dev;
707 if (dev->type != &i2c_adapter_type)
709 adap = to_i2c_adapter(dev);
711 i2c_dev = i2c_dev_get_by_minor(adap->nr);
712 if (!i2c_dev) /* attach_adapter must have failed */
715 put_i2c_dev(i2c_dev, true);
717 pr_debug("adapter [%s] unregistered\n", adap->name);
721 static int i2cdev_notifier_call(struct notifier_block *nb, unsigned long action,
724 struct device *dev = data;
727 case BUS_NOTIFY_ADD_DEVICE:
728 return i2cdev_attach_adapter(dev);
729 case BUS_NOTIFY_DEL_DEVICE:
730 return i2cdev_detach_adapter(dev);
736 static struct notifier_block i2cdev_notifier = {
737 .notifier_call = i2cdev_notifier_call,
740 /* ------------------------------------------------------------------------- */
742 static int __init i2c_dev_attach_adapter(struct device *dev, void *dummy)
744 i2cdev_attach_adapter(dev);
748 static int __exit i2c_dev_detach_adapter(struct device *dev, void *dummy)
750 i2cdev_detach_adapter(dev);
755 * module load/unload record keeping
758 static int __init i2c_dev_init(void)
762 pr_info("i2c /dev entries driver\n");
764 res = register_chrdev_region(MKDEV(I2C_MAJOR, 0), I2C_MINORS, "i2c");
768 res = class_register(&i2c_dev_class);
770 goto out_unreg_chrdev;
772 /* Keep track of adapters which will be added or removed later */
773 res = bus_register_notifier(&i2c_bus_type, &i2cdev_notifier);
775 goto out_unreg_class;
777 /* Bind to already existing adapters right away */
778 i2c_for_each_dev(NULL, i2c_dev_attach_adapter);
783 class_unregister(&i2c_dev_class);
785 unregister_chrdev_region(MKDEV(I2C_MAJOR, 0), I2C_MINORS);
787 pr_err("Driver Initialisation failed\n");
791 static void __exit i2c_dev_exit(void)
793 bus_unregister_notifier(&i2c_bus_type, &i2cdev_notifier);
794 i2c_for_each_dev(NULL, i2c_dev_detach_adapter);
795 class_unregister(&i2c_dev_class);
796 unregister_chrdev_region(MKDEV(I2C_MAJOR, 0), I2C_MINORS);
799 MODULE_AUTHOR("Frodo Looijaard <frodol@dds.nl>");
800 MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
801 MODULE_DESCRIPTION("I2C /dev entries driver");
802 MODULE_LICENSE("GPL");
804 module_init(i2c_dev_init);
805 module_exit(i2c_dev_exit);