Merge branch 'master'
[linux-2.6] / drivers / char / raw.c
1 /*
2  * linux/drivers/char/raw.c
3  *
4  * Front-end raw character devices.  These can be bound to any block
5  * devices to provide genuine Unix raw character device semantics.
6  *
7  * We reserve minor number 0 for a control interface.  ioctl()s on this
8  * device are used to bind the other minor numbers to block devices.
9  */
10
11 #include <linux/init.h>
12 #include <linux/fs.h>
13 #include <linux/devfs_fs_kernel.h>
14 #include <linux/major.h>
15 #include <linux/blkdev.h>
16 #include <linux/module.h>
17 #include <linux/raw.h>
18 #include <linux/capability.h>
19 #include <linux/uio.h>
20 #include <linux/cdev.h>
21 #include <linux/device.h>
22 #include <linux/mutex.h>
23
24 #include <asm/uaccess.h>
25
26 struct raw_device_data {
27         struct block_device *binding;
28         int inuse;
29 };
30
31 static struct class *raw_class;
32 static struct raw_device_data raw_devices[MAX_RAW_MINORS];
33 static DEFINE_MUTEX(raw_mutex);
34 static struct file_operations raw_ctl_fops;          /* forward declaration */
35
36 /*
37  * Open/close code for raw IO.
38  *
39  * We just rewrite the i_mapping for the /dev/raw/rawN file descriptor to
40  * point at the blockdev's address_space and set the file handle to use
41  * O_DIRECT.
42  *
43  * Set the device's soft blocksize to the minimum possible.  This gives the
44  * finest possible alignment and has no adverse impact on performance.
45  */
46 static int raw_open(struct inode *inode, struct file *filp)
47 {
48         const int minor = iminor(inode);
49         struct block_device *bdev;
50         int err;
51
52         if (minor == 0) {       /* It is the control device */
53                 filp->f_op = &raw_ctl_fops;
54                 return 0;
55         }
56
57         mutex_lock(&raw_mutex);
58
59         /*
60          * All we need to do on open is check that the device is bound.
61          */
62         bdev = raw_devices[minor].binding;
63         err = -ENODEV;
64         if (!bdev)
65                 goto out;
66         igrab(bdev->bd_inode);
67         err = blkdev_get(bdev, filp->f_mode, 0);
68         if (err)
69                 goto out;
70         err = bd_claim(bdev, raw_open);
71         if (err)
72                 goto out1;
73         err = set_blocksize(bdev, bdev_hardsect_size(bdev));
74         if (err)
75                 goto out2;
76         filp->f_flags |= O_DIRECT;
77         filp->f_mapping = bdev->bd_inode->i_mapping;
78         if (++raw_devices[minor].inuse == 1)
79                 filp->f_dentry->d_inode->i_mapping =
80                         bdev->bd_inode->i_mapping;
81         filp->private_data = bdev;
82         mutex_unlock(&raw_mutex);
83         return 0;
84
85 out2:
86         bd_release(bdev);
87 out1:
88         blkdev_put(bdev);
89 out:
90         mutex_unlock(&raw_mutex);
91         return err;
92 }
93
94 /*
95  * When the final fd which refers to this character-special node is closed, we
96  * make its ->mapping point back at its own i_data.
97  */
98 static int raw_release(struct inode *inode, struct file *filp)
99 {
100         const int minor= iminor(inode);
101         struct block_device *bdev;
102
103         mutex_lock(&raw_mutex);
104         bdev = raw_devices[minor].binding;
105         if (--raw_devices[minor].inuse == 0) {
106                 /* Here  inode->i_mapping == bdev->bd_inode->i_mapping  */
107                 inode->i_mapping = &inode->i_data;
108                 inode->i_mapping->backing_dev_info = &default_backing_dev_info;
109         }
110         mutex_unlock(&raw_mutex);
111
112         bd_release(bdev);
113         blkdev_put(bdev);
114         return 0;
115 }
116
117 /*
118  * Forward ioctls to the underlying block device.
119  */
120 static int
121 raw_ioctl(struct inode *inode, struct file *filp,
122                   unsigned int command, unsigned long arg)
123 {
124         struct block_device *bdev = filp->private_data;
125
126         return blkdev_ioctl(bdev->bd_inode, NULL, command, arg);
127 }
128
129 static void bind_device(struct raw_config_request *rq)
130 {
131         class_device_destroy(raw_class, MKDEV(RAW_MAJOR, rq->raw_minor));
132         class_device_create(raw_class, NULL, MKDEV(RAW_MAJOR, rq->raw_minor),
133                                       NULL, "raw%d", rq->raw_minor);
134 }
135
136 /*
137  * Deal with ioctls against the raw-device control interface, to bind
138  * and unbind other raw devices.
139  */
140 static int raw_ctl_ioctl(struct inode *inode, struct file *filp,
141                         unsigned int command, unsigned long arg)
142 {
143         struct raw_config_request rq;
144         struct raw_device_data *rawdev;
145         int err = 0;
146
147         switch (command) {
148         case RAW_SETBIND:
149         case RAW_GETBIND:
150
151                 /* First, find out which raw minor we want */
152
153                 if (copy_from_user(&rq, (void __user *) arg, sizeof(rq))) {
154                         err = -EFAULT;
155                         goto out;
156                 }
157
158                 if (rq.raw_minor < 0 || rq.raw_minor >= MAX_RAW_MINORS) {
159                         err = -EINVAL;
160                         goto out;
161                 }
162                 rawdev = &raw_devices[rq.raw_minor];
163
164                 if (command == RAW_SETBIND) {
165                         dev_t dev;
166
167                         /*
168                          * This is like making block devices, so demand the
169                          * same capability
170                          */
171                         if (!capable(CAP_SYS_ADMIN)) {
172                                 err = -EPERM;
173                                 goto out;
174                         }
175
176                         /*
177                          * For now, we don't need to check that the underlying
178                          * block device is present or not: we can do that when
179                          * the raw device is opened.  Just check that the
180                          * major/minor numbers make sense.
181                          */
182
183                         dev = MKDEV(rq.block_major, rq.block_minor);
184                         if ((rq.block_major == 0 && rq.block_minor != 0) ||
185                                         MAJOR(dev) != rq.block_major ||
186                                         MINOR(dev) != rq.block_minor) {
187                                 err = -EINVAL;
188                                 goto out;
189                         }
190
191                         mutex_lock(&raw_mutex);
192                         if (rawdev->inuse) {
193                                 mutex_unlock(&raw_mutex);
194                                 err = -EBUSY;
195                                 goto out;
196                         }
197                         if (rawdev->binding) {
198                                 bdput(rawdev->binding);
199                                 module_put(THIS_MODULE);
200                         }
201                         if (rq.block_major == 0 && rq.block_minor == 0) {
202                                 /* unbind */
203                                 rawdev->binding = NULL;
204                                 class_device_destroy(raw_class,
205                                                 MKDEV(RAW_MAJOR, rq.raw_minor));
206                         } else {
207                                 rawdev->binding = bdget(dev);
208                                 if (rawdev->binding == NULL)
209                                         err = -ENOMEM;
210                                 else {
211                                         __module_get(THIS_MODULE);
212                                         bind_device(&rq);
213                                 }
214                         }
215                         mutex_unlock(&raw_mutex);
216                 } else {
217                         struct block_device *bdev;
218
219                         mutex_lock(&raw_mutex);
220                         bdev = rawdev->binding;
221                         if (bdev) {
222                                 rq.block_major = MAJOR(bdev->bd_dev);
223                                 rq.block_minor = MINOR(bdev->bd_dev);
224                         } else {
225                                 rq.block_major = rq.block_minor = 0;
226                         }
227                         mutex_unlock(&raw_mutex);
228                         if (copy_to_user((void __user *)arg, &rq, sizeof(rq))) {
229                                 err = -EFAULT;
230                                 goto out;
231                         }
232                 }
233                 break;
234         default:
235                 err = -EINVAL;
236                 break;
237         }
238 out:
239         return err;
240 }
241
242 static ssize_t raw_file_write(struct file *file, const char __user *buf,
243                                    size_t count, loff_t *ppos)
244 {
245         struct iovec local_iov = {
246                 .iov_base = (char __user *)buf,
247                 .iov_len = count
248         };
249
250         return generic_file_write_nolock(file, &local_iov, 1, ppos);
251 }
252
253 static ssize_t raw_file_aio_write(struct kiocb *iocb, const char __user *buf,
254                                         size_t count, loff_t pos)
255 {
256         struct iovec local_iov = {
257                 .iov_base = (char __user *)buf,
258                 .iov_len = count
259         };
260
261         return generic_file_aio_write_nolock(iocb, &local_iov, 1, &iocb->ki_pos);
262 }
263
264
265 static struct file_operations raw_fops = {
266         .read   =       generic_file_read,
267         .aio_read =     generic_file_aio_read,
268         .write  =       raw_file_write,
269         .aio_write =    raw_file_aio_write,
270         .open   =       raw_open,
271         .release=       raw_release,
272         .ioctl  =       raw_ioctl,
273         .readv  =       generic_file_readv,
274         .writev =       generic_file_writev,
275         .owner  =       THIS_MODULE,
276 };
277
278 static struct file_operations raw_ctl_fops = {
279         .ioctl  =       raw_ctl_ioctl,
280         .open   =       raw_open,
281         .owner  =       THIS_MODULE,
282 };
283
284 static struct cdev raw_cdev = {
285         .kobj   =       {.name = "raw", },
286         .owner  =       THIS_MODULE,
287 };
288
289 static int __init raw_init(void)
290 {
291         int i;
292         dev_t dev = MKDEV(RAW_MAJOR, 0);
293
294         if (register_chrdev_region(dev, MAX_RAW_MINORS, "raw"))
295                 goto error;
296
297         cdev_init(&raw_cdev, &raw_fops);
298         if (cdev_add(&raw_cdev, dev, MAX_RAW_MINORS)) {
299                 kobject_put(&raw_cdev.kobj);
300                 unregister_chrdev_region(dev, MAX_RAW_MINORS);
301                 goto error;
302         }
303
304         raw_class = class_create(THIS_MODULE, "raw");
305         if (IS_ERR(raw_class)) {
306                 printk(KERN_ERR "Error creating raw class.\n");
307                 cdev_del(&raw_cdev);
308                 unregister_chrdev_region(dev, MAX_RAW_MINORS);
309                 goto error;
310         }
311         class_device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), NULL, "rawctl");
312
313         devfs_mk_cdev(MKDEV(RAW_MAJOR, 0),
314                       S_IFCHR | S_IRUGO | S_IWUGO,
315                       "raw/rawctl");
316         for (i = 1; i < MAX_RAW_MINORS; i++)
317                 devfs_mk_cdev(MKDEV(RAW_MAJOR, i),
318                               S_IFCHR | S_IRUGO | S_IWUGO,
319                               "raw/raw%d", i);
320         return 0;
321
322 error:
323         printk(KERN_ERR "error register raw device\n");
324         return 1;
325 }
326
327 static void __exit raw_exit(void)
328 {
329         int i;
330
331         for (i = 1; i < MAX_RAW_MINORS; i++)
332                 devfs_remove("raw/raw%d", i);
333         devfs_remove("raw/rawctl");
334         devfs_remove("raw");
335         class_device_destroy(raw_class, MKDEV(RAW_MAJOR, 0));
336         class_destroy(raw_class);
337         cdev_del(&raw_cdev);
338         unregister_chrdev_region(MKDEV(RAW_MAJOR, 0), MAX_RAW_MINORS);
339 }
340
341 module_init(raw_init);
342 module_exit(raw_exit);
343 MODULE_LICENSE("GPL");