1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * Support for dynamic clock devices
4 *
5 * Copyright (C) 2010 OMICRON electronics GmbH
6 */
7#include <linux/device.h>
8#include <linux/export.h>
9#include <linux/file.h>
10#include <linux/posix-clock.h>
11#include <linux/slab.h>
12#include <linux/syscalls.h>
13#include <linux/uaccess.h>
14
15#include "posix-timers.h"
16
17/*
18 * Returns NULL if the posix_clock instance attached to 'fp' is old and stale.
19 */
20static struct posix_clock *get_posix_clock(struct file *fp)
21{
22 struct posix_clock_context *pccontext = fp->private_data;
23 struct posix_clock *clk = pccontext->clk;
24
25 down_read(sem: &clk->rwsem);
26
27 if (!clk->zombie)
28 return clk;
29
30 up_read(sem: &clk->rwsem);
31
32 return NULL;
33}
34
35static void put_posix_clock(struct posix_clock *clk)
36{
37 up_read(sem: &clk->rwsem);
38}
39
40static ssize_t posix_clock_read(struct file *fp, char __user *buf,
41 size_t count, loff_t *ppos)
42{
43 struct posix_clock_context *pccontext = fp->private_data;
44 struct posix_clock *clk = get_posix_clock(fp);
45 int err = -EINVAL;
46
47 if (!clk)
48 return -ENODEV;
49
50 if (clk->ops.read)
51 err = clk->ops.read(pccontext, fp->f_flags, buf, count);
52
53 put_posix_clock(clk);
54
55 return err;
56}
57
58static __poll_t posix_clock_poll(struct file *fp, poll_table *wait)
59{
60 struct posix_clock_context *pccontext = fp->private_data;
61 struct posix_clock *clk = get_posix_clock(fp);
62 __poll_t result = 0;
63
64 if (!clk)
65 return EPOLLERR;
66
67 if (clk->ops.poll)
68 result = clk->ops.poll(pccontext, fp, wait);
69
70 put_posix_clock(clk);
71
72 return result;
73}
74
75static long posix_clock_ioctl(struct file *fp,
76 unsigned int cmd, unsigned long arg)
77{
78 struct posix_clock_context *pccontext = fp->private_data;
79 struct posix_clock *clk = get_posix_clock(fp);
80 int err = -ENOTTY;
81
82 if (!clk)
83 return -ENODEV;
84
85 if (clk->ops.ioctl)
86 err = clk->ops.ioctl(pccontext, cmd, arg);
87
88 put_posix_clock(clk);
89
90 return err;
91}
92
93static int posix_clock_open(struct inode *inode, struct file *fp)
94{
95 int err;
96 struct posix_clock *clk =
97 container_of(inode->i_cdev, struct posix_clock, cdev);
98 struct posix_clock_context *pccontext;
99
100 down_read(sem: &clk->rwsem);
101
102 if (clk->zombie) {
103 err = -ENODEV;
104 goto out;
105 }
106 pccontext = kzalloc(sizeof(*pccontext), GFP_KERNEL);
107 if (!pccontext) {
108 err = -ENOMEM;
109 goto out;
110 }
111 pccontext->clk = clk;
112 pccontext->fp = fp;
113 if (clk->ops.open) {
114 err = clk->ops.open(pccontext, fp->f_mode);
115 if (err) {
116 kfree(objp: pccontext);
117 goto out;
118 }
119 }
120
121 fp->private_data = pccontext;
122 get_device(dev: clk->dev);
123 err = 0;
124out:
125 up_read(sem: &clk->rwsem);
126 return err;
127}
128
129static int posix_clock_release(struct inode *inode, struct file *fp)
130{
131 struct posix_clock_context *pccontext = fp->private_data;
132 struct posix_clock *clk;
133 int err = 0;
134
135 if (!pccontext)
136 return -ENODEV;
137 clk = pccontext->clk;
138
139 if (clk->ops.release)
140 err = clk->ops.release(pccontext);
141
142 put_device(dev: clk->dev);
143
144 kfree(objp: pccontext);
145 fp->private_data = NULL;
146
147 return err;
148}
149
150static const struct file_operations posix_clock_file_operations = {
151 .owner = THIS_MODULE,
152 .read = posix_clock_read,
153 .poll = posix_clock_poll,
154 .unlocked_ioctl = posix_clock_ioctl,
155 .compat_ioctl = posix_clock_ioctl,
156 .open = posix_clock_open,
157 .release = posix_clock_release,
158};
159
160int posix_clock_register(struct posix_clock *clk, struct device *dev)
161{
162 int err;
163
164 init_rwsem(&clk->rwsem);
165
166 cdev_init(&clk->cdev, &posix_clock_file_operations);
167 err = cdev_device_add(cdev: &clk->cdev, dev);
168 if (err) {
169 pr_err("%s unable to add device %d:%d\n",
170 dev_name(dev), MAJOR(dev->devt), MINOR(dev->devt));
171 return err;
172 }
173 clk->cdev.owner = clk->ops.owner;
174 clk->dev = dev;
175
176 return 0;
177}
178EXPORT_SYMBOL_GPL(posix_clock_register);
179
180void posix_clock_unregister(struct posix_clock *clk)
181{
182 cdev_device_del(cdev: &clk->cdev, dev: clk->dev);
183
184 down_write(sem: &clk->rwsem);
185 clk->zombie = true;
186 up_write(sem: &clk->rwsem);
187
188 put_device(dev: clk->dev);
189}
190EXPORT_SYMBOL_GPL(posix_clock_unregister);
191
192struct posix_clock_desc {
193 struct file *fp;
194 struct posix_clock *clk;
195};
196
197static int get_clock_desc(const clockid_t id, struct posix_clock_desc *cd)
198{
199 struct file *fp = fget(fd: clockid_to_fd(clk: id));
200 int err = -EINVAL;
201
202 if (!fp)
203 return err;
204
205 if (fp->f_op->open != posix_clock_open || !fp->private_data)
206 goto out;
207
208 cd->fp = fp;
209 cd->clk = get_posix_clock(fp);
210
211 err = cd->clk ? 0 : -ENODEV;
212out:
213 if (err)
214 fput(fp);
215 return err;
216}
217
218static void put_clock_desc(struct posix_clock_desc *cd)
219{
220 put_posix_clock(clk: cd->clk);
221 fput(cd->fp);
222}
223
224static int pc_clock_adjtime(clockid_t id, struct __kernel_timex *tx)
225{
226 struct posix_clock_desc cd;
227 int err;
228
229 err = get_clock_desc(id, cd: &cd);
230 if (err)
231 return err;
232
233 if (tx->modes && (cd.fp->f_mode & FMODE_WRITE) == 0) {
234 err = -EACCES;
235 goto out;
236 }
237
238 if (cd.clk->ops.clock_adjtime)
239 err = cd.clk->ops.clock_adjtime(cd.clk, tx);
240 else
241 err = -EOPNOTSUPP;
242out:
243 put_clock_desc(cd: &cd);
244
245 return err;
246}
247
248static int pc_clock_gettime(clockid_t id, struct timespec64 *ts)
249{
250 struct posix_clock_desc cd;
251 int err;
252
253 err = get_clock_desc(id, cd: &cd);
254 if (err)
255 return err;
256
257 if (cd.clk->ops.clock_gettime)
258 err = cd.clk->ops.clock_gettime(cd.clk, ts);
259 else
260 err = -EOPNOTSUPP;
261
262 put_clock_desc(cd: &cd);
263
264 return err;
265}
266
267static int pc_clock_getres(clockid_t id, struct timespec64 *ts)
268{
269 struct posix_clock_desc cd;
270 int err;
271
272 err = get_clock_desc(id, cd: &cd);
273 if (err)
274 return err;
275
276 if (cd.clk->ops.clock_getres)
277 err = cd.clk->ops.clock_getres(cd.clk, ts);
278 else
279 err = -EOPNOTSUPP;
280
281 put_clock_desc(cd: &cd);
282
283 return err;
284}
285
286static int pc_clock_settime(clockid_t id, const struct timespec64 *ts)
287{
288 struct posix_clock_desc cd;
289 int err;
290
291 if (!timespec64_valid_strict(ts))
292 return -EINVAL;
293
294 err = get_clock_desc(id, cd: &cd);
295 if (err)
296 return err;
297
298 if ((cd.fp->f_mode & FMODE_WRITE) == 0) {
299 err = -EACCES;
300 goto out;
301 }
302
303 if (cd.clk->ops.clock_settime)
304 err = cd.clk->ops.clock_settime(cd.clk, ts);
305 else
306 err = -EOPNOTSUPP;
307out:
308 put_clock_desc(cd: &cd);
309
310 return err;
311}
312
313const struct k_clock clock_posix_dynamic = {
314 .clock_getres = pc_clock_getres,
315 .clock_set = pc_clock_settime,
316 .clock_get_timespec = pc_clock_gettime,
317 .clock_adj = pc_clock_adjtime,
318};
319

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source code of linux/kernel/time/posix-clock.c