20d90e6a6e50fb41dfdd2601b1ae6617c40a6070
[linux-2.6.git] / 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/major.h>
14 #include <linux/blkdev.h>
15 #include <linux/module.h>
16 #include <linux/raw.h>
17 #include <linux/capability.h>
18 #include <linux/uio.h>
19 #include <linux/cdev.h>
20 #include <linux/device.h>
21 #include <linux/mutex.h>
22 #include <linux/smp_lock.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 const 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         lock_kernel();
58         mutex_lock(&raw_mutex);
59
60         /*
61          * All we need to do on open is check that the device is bound.
62          */
63         bdev = raw_devices[minor].binding;
64         err = -ENODEV;
65         if (!bdev)
66                 goto out;
67         igrab(bdev->bd_inode);
68         err = blkdev_get(bdev, filp->f_mode);
69         if (err)
70                 goto out;
71         err = bd_claim(bdev, raw_open);
72         if (err)
73                 goto out1;
74         err = set_blocksize(bdev, bdev_hardsect_size(bdev));
75         if (err)
76                 goto out2;
77         filp->f_flags |= O_DIRECT;
78         filp->f_mapping = bdev->bd_inode->i_mapping;
79         if (++raw_devices[minor].inuse == 1)
80                 filp->f_path.dentry->d_inode->i_mapping =
81                         bdev->bd_inode->i_mapping;
82         filp->private_data = bdev;
83         mutex_unlock(&raw_mutex);
84         unlock_kernel();
85         return 0;
86
87 out2:
88         bd_release(bdev);
89 out1:
90         blkdev_put(bdev, filp->f_mode);
91 out:
92         mutex_unlock(&raw_mutex);
93         unlock_kernel();
94         return err;
95 }
96
97 /*
98  * When the final fd which refers to this character-special node is closed, we
99  * make its ->mapping point back at its own i_data.
100  */
101 static int raw_release(struct inode *inode, struct file *filp)
102 {
103         const int minor= iminor(inode);
104         struct block_device *bdev;
105
106         mutex_lock(&raw_mutex);
107         bdev = raw_devices[minor].binding;
108         if (--raw_devices[minor].inuse == 0) {
109                 /* Here  inode->i_mapping == bdev->bd_inode->i_mapping  */
110                 inode->i_mapping = &inode->i_data;
111                 inode->i_mapping->backing_dev_info = &default_backing_dev_info;
112         }
113         mutex_unlock(&raw_mutex);
114
115         bd_release(bdev);
116         blkdev_put(bdev, filp->f_mode);
117         return 0;
118 }
119
120 /*
121  * Forward ioctls to the underlying block device.
122  */
123 static int
124 raw_ioctl(struct inode *inode, struct file *filp,
125                   unsigned int command, unsigned long arg)
126 {
127         struct block_device *bdev = filp->private_data;
128
129         return blkdev_ioctl(bdev, 0, command, arg);
130 }
131
132 static void bind_device(struct raw_config_request *rq)
133 {
134         device_destroy(raw_class, MKDEV(RAW_MAJOR, rq->raw_minor));
135         device_create(raw_class, NULL, MKDEV(RAW_MAJOR, rq->raw_minor), NULL,
136                       "raw%d", rq->raw_minor);
137 }
138
139 /*
140  * Deal with ioctls against the raw-device control interface, to bind
141  * and unbind other raw devices.
142  */
143 static int raw_ctl_ioctl(struct inode *inode, struct file *filp,
144                         unsigned int command, unsigned long arg)
145 {
146         struct raw_config_request rq;
147         struct raw_device_data *rawdev;
148         int err = 0;
149
150         switch (command) {
151         case RAW_SETBIND:
152         case RAW_GETBIND:
153
154                 /* First, find out which raw minor we want */
155
156                 if (copy_from_user(&rq, (void __user *) arg, sizeof(rq))) {
157                         err = -EFAULT;
158                         goto out;
159                 }
160
161                 if (rq.raw_minor <= 0 || rq.raw_minor >= MAX_RAW_MINORS) {
162                         err = -EINVAL;
163                         goto out;
164                 }
165                 rawdev = &raw_devices[rq.raw_minor];
166
167                 if (command == RAW_SETBIND) {
168                         dev_t dev;
169
170                         /*
171                          * This is like making block devices, so demand the
172                          * same capability
173                          */
174                         if (!capable(CAP_SYS_ADMIN)) {
175                                 err = -EPERM;
176                                 goto out;
177                         }
178
179                         /*
180                          * For now, we don't need to check that the underlying
181                          * block device is present or not: we can do that when
182                          * the raw device is opened.  Just check that the
183                          * major/minor numbers make sense.
184                          */
185
186                         dev = MKDEV(rq.block_major, rq.block_minor);
187                         if ((rq.block_major == 0 && rq.block_minor != 0) ||
188                                         MAJOR(dev) != rq.block_major ||
189                                         MINOR(dev) != rq.block_minor) {
190                                 err = -EINVAL;
191                                 goto out;
192                         }
193
194                         mutex_lock(&raw_mutex);
195                         if (rawdev->inuse) {
196                                 mutex_unlock(&raw_mutex);
197                                 err = -EBUSY;
198                                 goto out;
199                         }
200                         if (rawdev->binding) {
201                                 bdput(rawdev->binding);
202                                 module_put(THIS_MODULE);
203                         }
204                         if (rq.block_major == 0 && rq.block_minor == 0) {
205                                 /* unbind */
206                                 rawdev->binding = NULL;
207                                 device_destroy(raw_class,
208                                                 MKDEV(RAW_MAJOR, rq.raw_minor));
209                         } else {
210                                 rawdev->binding = bdget(dev);
211                                 if (rawdev->binding == NULL)
212                                         err = -ENOMEM;
213                                 else {
214                                         __module_get(THIS_MODULE);
215                                         bind_device(&rq);
216                                 }
217                         }
218                         mutex_unlock(&raw_mutex);
219                 } else {
220                         struct block_device *bdev;
221
222                         mutex_lock(&raw_mutex);
223                         bdev = rawdev->binding;
224                         if (bdev) {
225                                 rq.block_major = MAJOR(bdev->bd_dev);
226                                 rq.block_minor = MINOR(bdev->bd_dev);
227                         } else {
228                                 rq.block_major = rq.block_minor = 0;
229                         }
230                         mutex_unlock(&raw_mutex);
231                         if (copy_to_user((void __user *)arg, &rq, sizeof(rq))) {
232                                 err = -EFAULT;
233                                 goto out;
234                         }
235                 }
236                 break;
237         default:
238                 err = -EINVAL;
239                 break;
240         }
241 out:
242         return err;
243 }
244
245 static const struct file_operations raw_fops = {
246         .read   =       do_sync_read,
247         .aio_read =     generic_file_aio_read,
248         .write  =       do_sync_write,
249         .aio_write =    generic_file_aio_write_nolock,
250         .open   =       raw_open,
251         .release=       raw_release,
252         .ioctl  =       raw_ioctl,
253         .owner  =       THIS_MODULE,
254 };
255
256 static const struct file_operations raw_ctl_fops = {
257         .ioctl  =       raw_ctl_ioctl,
258         .open   =       raw_open,
259         .owner  =       THIS_MODULE,
260 };
261
262 static struct cdev raw_cdev;
263
264 static int __init raw_init(void)
265 {
266         dev_t dev = MKDEV(RAW_MAJOR, 0);
267         int ret;
268
269         ret = register_chrdev_region(dev, MAX_RAW_MINORS, "raw");
270         if (ret)
271                 goto error;
272
273         cdev_init(&raw_cdev, &raw_fops);
274         ret = cdev_add(&raw_cdev, dev, MAX_RAW_MINORS);
275         if (ret) {
276                 kobject_put(&raw_cdev.kobj);
277                 goto error_region;
278         }
279
280         raw_class = class_create(THIS_MODULE, "raw");
281         if (IS_ERR(raw_class)) {
282                 printk(KERN_ERR "Error creating raw class.\n");
283                 cdev_del(&raw_cdev);
284                 ret = PTR_ERR(raw_class);
285                 goto error_region;
286         }
287         device_create(raw_class, NULL, MKDEV(RAW_MAJOR, 0), NULL, "rawctl");
288
289         return 0;
290
291 error_region:
292         unregister_chrdev_region(dev, MAX_RAW_MINORS);
293 error:
294         return ret;
295 }
296
297 static void __exit raw_exit(void)
298 {
299         device_destroy(raw_class, MKDEV(RAW_MAJOR, 0));
300         class_destroy(raw_class);
301         cdev_del(&raw_cdev);
302         unregister_chrdev_region(MKDEV(RAW_MAJOR, 0), MAX_RAW_MINORS);
303 }
304
305 module_init(raw_init);
306 module_exit(raw_exit);
307 MODULE_LICENSE("GPL");