xref: /linux/drivers/pps/pps.c (revision 3630400697a3d334a391c1dba1b601d852145f2c) 
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * PPS core file
4  *
5  * Copyright (C) 2005-2009   Rodolfo Giometti <giometti@linux.it>
6  */
7 
8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9 
10 #include <linux/kernel.h>
11 #include <linux/module.h>
12 #include <linux/init.h>
13 #include <linux/sched.h>
14 #include <linux/uaccess.h>
15 #include <linux/idr.h>
16 #include <linux/mutex.h>
17 #include <linux/cdev.h>
18 #include <linux/poll.h>
19 #include <linux/pps_kernel.h>
20 #include <linux/slab.h>
21 
22 #include "kc.h"
23 
24 /*
25  * Local variables
26  */
27 
28 static dev_t pps_devt;
29 static struct class *pps_class;
30 
31 static DEFINE_MUTEX(pps_idr_lock);
32 static DEFINE_IDR(pps_idr);
33 
34 /*
35  * Char device methods
36  */
37 
38 static __poll_t pps_cdev_poll(struct file *file, poll_table *wait)
39 {
40 	struct pps_device *pps = file->private_data;
41 
42 	poll_wait(file, &pps->queue, wait);
43 
44 	return EPOLLIN | EPOLLRDNORM;
45 }
46 
47 static int pps_cdev_fasync(int fd, struct file *file, int on)
48 {
49 	struct pps_device *pps = file->private_data;
50 	return fasync_helper(fd, file, on, &pps->async_queue);
51 }
52 
53 static int pps_cdev_pps_fetch(struct pps_device *pps, struct pps_fdata *fdata)
54 {
55 	unsigned int ev = pps->last_ev;
56 	int err = 0;
57 
58 	/* Manage the timeout */
59 	if (fdata->timeout.flags & PPS_TIME_INVALID)
60 		err = wait_event_interruptible(pps->queue,
61 				ev != pps->last_ev);
62 	else {
63 		unsigned long ticks;
64 
65 		dev_dbg(pps->dev, "timeout %lld.%09d\n",
66 				(long long) fdata->timeout.sec,
67 				fdata->timeout.nsec);
68 		ticks = fdata->timeout.sec * HZ;
69 		ticks += fdata->timeout.nsec / (NSEC_PER_SEC / HZ);
70 
71 		if (ticks != 0) {
72 			err = wait_event_interruptible_timeout(
73 					pps->queue,
74 					ev != pps->last_ev,
75 					ticks);
76 			if (err == 0)
77 				return -ETIMEDOUT;
78 		}
79 	}
80 
81 	/* Check for pending signals */
82 	if (err == -ERESTARTSYS) {
83 		dev_dbg(pps->dev, "pending signal caught\n");
84 		return -EINTR;
85 	}
86 
87 	return 0;
88 }
89 
90 static long pps_cdev_ioctl(struct file *file,
91 		unsigned int cmd, unsigned long arg)
92 {
93 	struct pps_device *pps = file->private_data;
94 	struct pps_kparams params;
95 	void __user *uarg = (void __user *) arg;
96 	int __user *iuarg = (int __user *) arg;
97 	int err;
98 
99 	switch (cmd) {
100 	case PPS_GETPARAMS:
101 		dev_dbg(pps->dev, "PPS_GETPARAMS\n");
102 
103 		spin_lock_irq(&pps->lock);
104 
105 		/* Get the current parameters */
106 		params = pps->params;
107 
108 		spin_unlock_irq(&pps->lock);
109 
110 		err = copy_to_user(uarg, &params, sizeof(struct pps_kparams));
111 		if (err)
112 			return -EFAULT;
113 
114 		break;
115 
116 	case PPS_SETPARAMS:
117 		dev_dbg(pps->dev, "PPS_SETPARAMS\n");
118 
119 		/* Check the capabilities */
120 		if (!capable(CAP_SYS_TIME))
121 			return -EPERM;
122 
123 		err = copy_from_user(&params, uarg, sizeof(struct pps_kparams));
124 		if (err)
125 			return -EFAULT;
126 		if (!(params.mode & (PPS_CAPTUREASSERT | PPS_CAPTURECLEAR))) {
127 			dev_dbg(pps->dev, "capture mode unspecified (%x)\n",
128 								params.mode);
129 			return -EINVAL;
130 		}
131 
132 		/* Check for supported capabilities */
133 		if ((params.mode & ~pps->info.mode) != 0) {
134 			dev_dbg(pps->dev, "unsupported capabilities (%x)\n",
135 								params.mode);
136 			return -EINVAL;
137 		}
138 
139 		spin_lock_irq(&pps->lock);
140 
141 		/* Save the new parameters */
142 		pps->params = params;
143 
144 		/* Restore the read only parameters */
145 		if ((params.mode & (PPS_TSFMT_TSPEC | PPS_TSFMT_NTPFP)) == 0) {
146 			/* section 3.3 of RFC 2783 interpreted */
147 			dev_dbg(pps->dev, "time format unspecified (%x)\n",
148 								params.mode);
149 			pps->params.mode |= PPS_TSFMT_TSPEC;
150 		}
151 		if (pps->info.mode & PPS_CANWAIT)
152 			pps->params.mode |= PPS_CANWAIT;
153 		pps->params.api_version = PPS_API_VERS;
154 
155 		/*
156 		 * Clear unused fields of pps_kparams to avoid leaking
157 		 * uninitialized data of the PPS_SETPARAMS caller via
158 		 * PPS_GETPARAMS
159 		 */
160 		pps->params.assert_off_tu.flags = 0;
161 		pps->params.clear_off_tu.flags = 0;
162 
163 		spin_unlock_irq(&pps->lock);
164 
165 		break;
166 
167 	case PPS_GETCAP:
168 		dev_dbg(pps->dev, "PPS_GETCAP\n");
169 
170 		err = put_user(pps->info.mode, iuarg);
171 		if (err)
172 			return -EFAULT;
173 
174 		break;
175 
176 	case PPS_FETCH: {
177 		struct pps_fdata fdata;
178 
179 		dev_dbg(pps->dev, "PPS_FETCH\n");
180 
181 		err = copy_from_user(&fdata, uarg, sizeof(struct pps_fdata));
182 		if (err)
183 			return -EFAULT;
184 
185 		err = pps_cdev_pps_fetch(pps, &fdata);
186 		if (err)
187 			return err;
188 
189 		/* Return the fetched timestamp */
190 		spin_lock_irq(&pps->lock);
191 
192 		fdata.info.assert_sequence = pps->assert_sequence;
193 		fdata.info.clear_sequence = pps->clear_sequence;
194 		fdata.info.assert_tu = pps->assert_tu;
195 		fdata.info.clear_tu = pps->clear_tu;
196 		fdata.info.current_mode = pps->current_mode;
197 
198 		spin_unlock_irq(&pps->lock);
199 
200 		err = copy_to_user(uarg, &fdata, sizeof(struct pps_fdata));
201 		if (err)
202 			return -EFAULT;
203 
204 		break;
205 	}
206 	case PPS_KC_BIND: {
207 		struct pps_bind_args bind_args;
208 
209 		dev_dbg(pps->dev, "PPS_KC_BIND\n");
210 
211 		/* Check the capabilities */
212 		if (!capable(CAP_SYS_TIME))
213 			return -EPERM;
214 
215 		if (copy_from_user(&bind_args, uarg,
216 					sizeof(struct pps_bind_args)))
217 			return -EFAULT;
218 
219 		/* Check for supported capabilities */
220 		if ((bind_args.edge & ~pps->info.mode) != 0) {
221 			dev_err(pps->dev, "unsupported capabilities (%x)\n",
222 					bind_args.edge);
223 			return -EINVAL;
224 		}
225 
226 		/* Validate parameters roughly */
227 		if (bind_args.tsformat != PPS_TSFMT_TSPEC ||
228 				(bind_args.edge & ~PPS_CAPTUREBOTH) != 0 ||
229 				bind_args.consumer != PPS_KC_HARDPPS) {
230 			dev_err(pps->dev, "invalid kernel consumer bind"
231 					" parameters (%x)\n", bind_args.edge);
232 			return -EINVAL;
233 		}
234 
235 		err = pps_kc_bind(pps, &bind_args);
236 		if (err < 0)
237 			return err;
238 
239 		break;
240 	}
241 	default:
242 		return -ENOTTY;
243 	}
244 
245 	return 0;
246 }
247 
248 #ifdef CONFIG_COMPAT
249 static long pps_cdev_compat_ioctl(struct file *file,
250 		unsigned int cmd, unsigned long arg)
251 {
252 	struct pps_device *pps = file->private_data;
253 	void __user *uarg = (void __user *) arg;
254 
255 	cmd = _IOC(_IOC_DIR(cmd), _IOC_TYPE(cmd), _IOC_NR(cmd), sizeof(void *));
256 
257 	if (cmd == PPS_FETCH) {
258 		struct pps_fdata_compat compat;
259 		struct pps_fdata fdata;
260 		int err;
261 
262 		dev_dbg(pps->dev, "PPS_FETCH\n");
263 
264 		err = copy_from_user(&compat, uarg, sizeof(struct pps_fdata_compat));
265 		if (err)
266 			return -EFAULT;
267 
268 		memcpy(&fdata.timeout, &compat.timeout,
269 					sizeof(struct pps_ktime_compat));
270 
271 		err = pps_cdev_pps_fetch(pps, &fdata);
272 		if (err)
273 			return err;
274 
275 		/* Return the fetched timestamp */
276 		spin_lock_irq(&pps->lock);
277 
278 		compat.info.assert_sequence = pps->assert_sequence;
279 		compat.info.clear_sequence = pps->clear_sequence;
280 		compat.info.current_mode = pps->current_mode;
281 
282 		memcpy(&compat.info.assert_tu, &pps->assert_tu,
283 				sizeof(struct pps_ktime_compat));
284 		memcpy(&compat.info.clear_tu, &pps->clear_tu,
285 				sizeof(struct pps_ktime_compat));
286 
287 		spin_unlock_irq(&pps->lock);
288 
289 		return copy_to_user(uarg, &compat,
290 				sizeof(struct pps_fdata_compat)) ? -EFAULT : 0;
291 	}
292 
293 	return pps_cdev_ioctl(file, cmd, arg);
294 }
295 #else
296 #define pps_cdev_compat_ioctl	NULL
297 #endif
298 
299 static int pps_cdev_open(struct inode *inode, struct file *file)
300 {
301 	struct pps_device *pps = container_of(inode->i_cdev,
302 						struct pps_device, cdev);
303 	file->private_data = pps;
304 	kobject_get(&pps->dev->kobj);
305 	return 0;
306 }
307 
308 static int pps_cdev_release(struct inode *inode, struct file *file)
309 {
310 	struct pps_device *pps = container_of(inode->i_cdev,
311 						struct pps_device, cdev);
312 	kobject_put(&pps->dev->kobj);
313 	return 0;
314 }
315 
316 /*
317  * Char device stuff
318  */
319 
320 static const struct file_operations pps_cdev_fops = {
321 	.owner		= THIS_MODULE,
322 	.poll		= pps_cdev_poll,
323 	.fasync		= pps_cdev_fasync,
324 	.compat_ioctl	= pps_cdev_compat_ioctl,
325 	.unlocked_ioctl	= pps_cdev_ioctl,
326 	.open		= pps_cdev_open,
327 	.release	= pps_cdev_release,
328 };
329 
330 static void pps_device_destruct(struct device *dev)
331 {
332 	struct pps_device *pps = dev_get_drvdata(dev);
333 
334 	cdev_del(&pps->cdev);
335 
336 	/* Now we can release the ID for re-use */
337 	pr_debug("deallocating pps%d\n", pps->id);
338 	mutex_lock(&pps_idr_lock);
339 	idr_remove(&pps_idr, pps->id);
340 	mutex_unlock(&pps_idr_lock);
341 
342 	kfree(dev);
343 	kfree(pps);
344 }
345 
346 int pps_register_cdev(struct pps_device *pps)
347 {
348 	int err;
349 	dev_t devt;
350 
351 	mutex_lock(&pps_idr_lock);
352 	/*
353 	 * Get new ID for the new PPS source.  After idr_alloc() calling
354 	 * the new source will be freely available into the kernel.
355 	 */
356 	err = idr_alloc(&pps_idr, pps, 0, PPS_MAX_SOURCES, GFP_KERNEL);
357 	if (err < 0) {
358 		if (err == -ENOSPC) {
359 			pr_err("%s: too many PPS sources in the system\n",
360 			       pps->info.name);
361 			err = -EBUSY;
362 		}
363 		goto out_unlock;
364 	}
365 	pps->id = err;
366 	mutex_unlock(&pps_idr_lock);
367 
368 	devt = MKDEV(MAJOR(pps_devt), pps->id);
369 
370 	cdev_init(&pps->cdev, &pps_cdev_fops);
371 	pps->cdev.owner = pps->info.owner;
372 
373 	err = cdev_add(&pps->cdev, devt, 1);
374 	if (err) {
375 		pr_err("%s: failed to add char device %d:%d\n",
376 				pps->info.name, MAJOR(pps_devt), pps->id);
377 		goto free_idr;
378 	}
379 	pps->dev = device_create(pps_class, pps->info.dev, devt, pps,
380 							"pps%d", pps->id);
381 	if (IS_ERR(pps->dev)) {
382 		err = PTR_ERR(pps->dev);
383 		goto del_cdev;
384 	}
385 
386 	/* Override the release function with our own */
387 	pps->dev->release = pps_device_destruct;
388 
389 	pr_debug("source %s got cdev (%d:%d)\n", pps->info.name,
390 			MAJOR(pps_devt), pps->id);
391 
392 	return 0;
393 
394 del_cdev:
395 	cdev_del(&pps->cdev);
396 
397 free_idr:
398 	mutex_lock(&pps_idr_lock);
399 	idr_remove(&pps_idr, pps->id);
400 out_unlock:
401 	mutex_unlock(&pps_idr_lock);
402 	return err;
403 }
404 
405 void pps_unregister_cdev(struct pps_device *pps)
406 {
407 	pr_debug("unregistering pps%d\n", pps->id);
408 	pps->lookup_cookie = NULL;
409 	device_destroy(pps_class, pps->dev->devt);
410 }
411 
412 /*
413  * Look up a pps device by magic cookie.
414  * The cookie is usually a pointer to some enclosing device, but this
415  * code doesn't care; you should never be dereferencing it.
416  *
417  * This is a bit of a kludge that is currently used only by the PPS
418  * serial line discipline.  It may need to be tweaked when a second user
419  * is found.
420  *
421  * There is no function interface for setting the lookup_cookie field.
422  * It's initialized to NULL when the pps device is created, and if a
423  * client wants to use it, just fill it in afterward.
424  *
425  * The cookie is automatically set to NULL in pps_unregister_source()
426  * so that it will not be used again, even if the pps device cannot
427  * be removed from the idr due to pending references holding the minor
428  * number in use.
429  */
430 struct pps_device *pps_lookup_dev(void const *cookie)
431 {
432 	struct pps_device *pps;
433 	unsigned id;
434 
435 	rcu_read_lock();
436 	idr_for_each_entry(&pps_idr, pps, id)
437 		if (cookie == pps->lookup_cookie)
438 			break;
439 	rcu_read_unlock();
440 	return pps;
441 }
442 EXPORT_SYMBOL(pps_lookup_dev);
443 
444 /*
445  * Module stuff
446  */
447 
448 static void __exit pps_exit(void)
449 {
450 	class_destroy(pps_class);
451 	unregister_chrdev_region(pps_devt, PPS_MAX_SOURCES);
452 }
453 
454 static int __init pps_init(void)
455 {
456 	int err;
457 
458 	pps_class = class_create("pps");
459 	if (IS_ERR(pps_class)) {
460 		pr_err("failed to allocate class\n");
461 		return PTR_ERR(pps_class);
462 	}
463 	pps_class->dev_groups = pps_groups;
464 
465 	err = alloc_chrdev_region(&pps_devt, 0, PPS_MAX_SOURCES, "pps");
466 	if (err < 0) {
467 		pr_err("failed to allocate char device region\n");
468 		goto remove_class;
469 	}
470 
471 	pr_info("LinuxPPS API ver. %d registered\n", PPS_API_VERS);
472 	pr_info("Software ver. %s - Copyright 2005-2007 Rodolfo Giometti "
473 		"<giometti@linux.it>\n", PPS_VERSION);
474 
475 	return 0;
476 
477 remove_class:
478 	class_destroy(pps_class);
479 
480 	return err;
481 }
482 
483 subsys_initcall(pps_init);
484 module_exit(pps_exit);
485 
486 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
487 MODULE_DESCRIPTION("LinuxPPS support (RFC 2783) - ver. " PPS_VERSION);
488 MODULE_LICENSE("GPL");
489