serio_raw.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Raw serio device providing access to a raw byte stream from underlying
  4 * serio port. Closely emulates behavior of pre-2.6 /dev/psaux device
  5 *
  6 * Copyright (c) 2004 Dmitry Torokhov
  7 */
  8
  9#include <linux/kref.h>
 10#include <linux/sched.h>
 11#include <linux/slab.h>
 12#include <linux/poll.h>
 13#include <linux/module.h>
 14#include <linux/serio.h>
 15#include <linux/major.h>
 16#include <linux/device.h>
 17#include <linux/miscdevice.h>
 18#include <linux/wait.h>
 19#include <linux/mutex.h>
 20
 21#define DRIVER_DESC	"Raw serio driver"
 22
 23MODULE_AUTHOR("Dmitry Torokhov <dtor@mail.ru>");
 24MODULE_DESCRIPTION(DRIVER_DESC);
 25MODULE_LICENSE("GPL");
 26
 27#define SERIO_RAW_QUEUE_LEN	64
 28struct serio_raw {
 29	unsigned char queue[SERIO_RAW_QUEUE_LEN];
 30	unsigned int tail, head;
 31
 32	char name[20];
 33	struct kref kref;
 34	struct serio *serio;
 35	struct miscdevice dev;
 36	wait_queue_head_t wait;
 37	struct list_head client_list;
 38	struct list_head node;
 39	bool dead;
 40};
 41
 42struct serio_raw_client {
 43	struct fasync_struct *fasync;
 44	struct serio_raw *serio_raw;
 45	struct list_head node;
 46};
 47
 48static DEFINE_MUTEX(serio_raw_mutex);
 49static LIST_HEAD(serio_raw_list);
 50
 51/*********************************************************************
 52 *             Interface with userspace (file operations)            *
 53 *********************************************************************/
 54
 55static int serio_raw_fasync(int fd, struct file *file, int on)
 56{
 57	struct serio_raw_client *client = file->private_data;
 58
 59	return fasync_helper(fd, file, on, &client->fasync);
 60}
 61
 62static struct serio_raw *serio_raw_locate(int minor)
 63{
 64	struct serio_raw *serio_raw;
 65
 66	list_for_each_entry(serio_raw, &serio_raw_list, node) {
 67		if (serio_raw->dev.minor == minor)
 68			return serio_raw;
 69	}
 70
 71	return NULL;
 72}
 73
 74static int serio_raw_open(struct inode *inode, struct file *file)
 75{
 76	struct serio_raw *serio_raw;
 77	struct serio_raw_client *client;
 78
 79	scoped_guard(mutex_intr, &serio_raw_mutex) {
 80		serio_raw = serio_raw_locate(iminor(inode));
 81		if (!serio_raw)
 82			return -ENODEV;
 83
 84		if (serio_raw->dead)
 85			return -ENODEV;
 86
 87		client = kzalloc(sizeof(*client), GFP_KERNEL);
 88		if (!client)
 89			return -ENOMEM;
 90
 91		client->serio_raw = serio_raw;
 92		file->private_data = client;
 93
 94		kref_get(&serio_raw->kref);
 95
 96		scoped_guard(serio_pause_rx, serio_raw->serio)
 97			list_add_tail(&client->node, &serio_raw->client_list);
 98
 99		return 0;
100	}
101
102	return -EINTR;
103}
104
105static void serio_raw_free(struct kref *kref)
106{
107	struct serio_raw *serio_raw =
108			container_of(kref, struct serio_raw, kref);
109
110	put_device(&serio_raw->serio->dev);
111	kfree(serio_raw);
112}
113
114static int serio_raw_release(struct inode *inode, struct file *file)
115{
116	struct serio_raw_client *client = file->private_data;
117	struct serio_raw *serio_raw = client->serio_raw;
118
119	scoped_guard(serio_pause_rx, serio_raw->serio)
120		list_del(&client->node);
121
122	kfree(client);
123
124	kref_put(&serio_raw->kref, serio_raw_free);
125
126	return 0;
127}
128
129static bool serio_raw_fetch_byte(struct serio_raw *serio_raw, char *c)
130{
131	guard(serio_pause_rx)(serio_raw->serio);
132
133	if (serio_raw->head == serio_raw->tail)
134		return false; /* queue is empty */
135
136	*c = serio_raw->queue[serio_raw->tail];
137	serio_raw->tail = (serio_raw->tail + 1) % SERIO_RAW_QUEUE_LEN;
138
139	return true;
140}
141
142static ssize_t serio_raw_read(struct file *file, char __user *buffer,
143			      size_t count, loff_t *ppos)
144{
145	struct serio_raw_client *client = file->private_data;
146	struct serio_raw *serio_raw = client->serio_raw;
147	char c;
148	ssize_t read = 0;
149	int error;
150
151	for (;;) {
152		if (serio_raw->dead)
153			return -ENODEV;
154
155		if (serio_raw->head == serio_raw->tail &&
156		    (file->f_flags & O_NONBLOCK))
157			return -EAGAIN;
158
159		if (count == 0)
160			break;
161
162		while (read < count && serio_raw_fetch_byte(serio_raw, &c)) {
163			if (put_user(c, buffer++))
164				return -EFAULT;
165			read++;
166		}
167
168		if (read)
169			break;
170
171		if (!(file->f_flags & O_NONBLOCK)) {
172			error = wait_event_interruptible(serio_raw->wait,
173					serio_raw->head != serio_raw->tail ||
174					serio_raw->dead);
175			if (error)
176				return error;
177		}
178	}
179
180	return read;
181}
182
183static ssize_t serio_raw_write(struct file *file, const char __user *buffer,
184			       size_t count, loff_t *ppos)
185{
186	struct serio_raw_client *client = file->private_data;
187	struct serio_raw *serio_raw = client->serio_raw;
188	int written = 0;
189	unsigned char c;
190
191	scoped_guard(mutex_intr, &serio_raw_mutex) {
192		if (serio_raw->dead)
193			return -ENODEV;
194
195		if (count > 32)
196			count = 32;
197
198		while (count--) {
199			if (get_user(c, buffer++))
200				return -EFAULT;
201
202			if (serio_write(serio_raw->serio, c)) {
203				/* Either signal error or partial write */
204				return written ?: -EIO;
205			}
206
207			written++;
208		}
209
210		return written;
211	}
212
213	return -EINTR;
214}
215
216static __poll_t serio_raw_poll(struct file *file, poll_table *wait)
217{
218	struct serio_raw_client *client = file->private_data;
219	struct serio_raw *serio_raw = client->serio_raw;
220	__poll_t mask;
221
222	poll_wait(file, &serio_raw->wait, wait);
223
224	mask = serio_raw->dead ? EPOLLHUP | EPOLLERR : EPOLLOUT | EPOLLWRNORM;
225	if (serio_raw->head != serio_raw->tail)
226		mask |= EPOLLIN | EPOLLRDNORM;
227
228	return mask;
229}
230
231static const struct file_operations serio_raw_fops = {
232	.owner		= THIS_MODULE,
233	.open		= serio_raw_open,
234	.release	= serio_raw_release,
235	.read		= serio_raw_read,
236	.write		= serio_raw_write,
237	.poll		= serio_raw_poll,
238	.fasync		= serio_raw_fasync,
239	.llseek		= noop_llseek,
240};
241
242
243/*********************************************************************
244 *                   Interface with serio port                       *
245 *********************************************************************/
246
247static irqreturn_t serio_raw_interrupt(struct serio *serio, unsigned char data,
248					unsigned int dfl)
249{
250	struct serio_raw *serio_raw = serio_get_drvdata(serio);
251	struct serio_raw_client *client;
252	unsigned int head = serio_raw->head;
253
254	/* we are holding serio->lock here so we are protected */
255	serio_raw->queue[head] = data;
256	head = (head + 1) % SERIO_RAW_QUEUE_LEN;
257	if (likely(head != serio_raw->tail)) {
258		serio_raw->head = head;
259		list_for_each_entry(client, &serio_raw->client_list, node)
260			kill_fasync(&client->fasync, SIGIO, POLL_IN);
261		wake_up_interruptible(&serio_raw->wait);
262	}
263
264	return IRQ_HANDLED;
265}
266
267static int serio_raw_connect(struct serio *serio, struct serio_driver *drv)
268{
269	static atomic_t serio_raw_no = ATOMIC_INIT(-1);
270	struct serio_raw *serio_raw;
271	int err;
272
273	serio_raw = kzalloc(sizeof(*serio_raw), GFP_KERNEL);
274	if (!serio_raw) {
275		dev_dbg(&serio->dev, "can't allocate memory for a device\n");
276		return -ENOMEM;
277	}
278
279	snprintf(serio_raw->name, sizeof(serio_raw->name),
280		 "serio_raw%u", atomic_inc_return(&serio_raw_no));
281	kref_init(&serio_raw->kref);
282	INIT_LIST_HEAD(&serio_raw->client_list);
283	init_waitqueue_head(&serio_raw->wait);
284
285	serio_raw->serio = serio;
286	get_device(&serio->dev);
287
288	serio_set_drvdata(serio, serio_raw);
289
290	err = serio_open(serio, drv);
291	if (err)
292		goto err_free;
293
294	err = mutex_lock_killable(&serio_raw_mutex);
295	if (err)
296		goto err_close;
297
298	list_add_tail(&serio_raw->node, &serio_raw_list);
299	mutex_unlock(&serio_raw_mutex);
300
301	serio_raw->dev.minor = PSMOUSE_MINOR;
302	serio_raw->dev.name = serio_raw->name;
303	serio_raw->dev.parent = &serio->dev;
304	serio_raw->dev.fops = &serio_raw_fops;
305
306	err = misc_register(&serio_raw->dev);
307	if (err) {
308		serio_raw->dev.minor = MISC_DYNAMIC_MINOR;
309		err = misc_register(&serio_raw->dev);
310	}
311
312	if (err) {
313		dev_err(&serio->dev,
314			"failed to register raw access device for %s\n",
315			serio->phys);
316		goto err_unlink;
317	}
318
319	dev_info(&serio->dev, "raw access enabled on %s (%s, minor %d)\n",
320		 serio->phys, serio_raw->name, serio_raw->dev.minor);
321	return 0;
322
323err_unlink:
324	list_del_init(&serio_raw->node);
325err_close:
326	serio_close(serio);
327err_free:
328	serio_set_drvdata(serio, NULL);
329	kref_put(&serio_raw->kref, serio_raw_free);
330	return err;
331}
332
333static int serio_raw_reconnect(struct serio *serio)
334{
335	struct serio_raw *serio_raw = serio_get_drvdata(serio);
336	struct serio_driver *drv = serio->drv;
337
338	if (!drv || !serio_raw) {
339		dev_dbg(&serio->dev,
340			"reconnect request, but serio is disconnected, ignoring...\n");
341		return -1;
342	}
343
344	/*
345	 * Nothing needs to be done here, we just need this method to
346	 * keep the same device.
347	 */
348	return 0;
349}
350
351/*
352 * Wake up users waiting for IO so they can disconnect from
353 * dead device.
354 */
355static void serio_raw_hangup(struct serio_raw *serio_raw)
356{
357	struct serio_raw_client *client;
358
359	scoped_guard(serio_pause_rx, serio_raw->serio) {
360		list_for_each_entry(client, &serio_raw->client_list, node)
361			kill_fasync(&client->fasync, SIGIO, POLL_HUP);
362	}
363
364	wake_up_interruptible(&serio_raw->wait);
365}
366
367
368static void serio_raw_disconnect(struct serio *serio)
369{
370	struct serio_raw *serio_raw = serio_get_drvdata(serio);
371
372	misc_deregister(&serio_raw->dev);
373
374	scoped_guard(mutex, &serio_raw_mutex) {
375		serio_raw->dead = true;
376		list_del_init(&serio_raw->node);
377	}
378
379	serio_raw_hangup(serio_raw);
380
381	serio_close(serio);
382	kref_put(&serio_raw->kref, serio_raw_free);
383
384	serio_set_drvdata(serio, NULL);
385}
386
387static const struct serio_device_id serio_raw_serio_ids[] = {
388	{
389		.type	= SERIO_8042,
390		.proto	= SERIO_ANY,
391		.id	= SERIO_ANY,
392		.extra	= SERIO_ANY,
393	},
394	{
395		.type	= SERIO_8042_XL,
396		.proto	= SERIO_ANY,
397		.id	= SERIO_ANY,
398		.extra	= SERIO_ANY,
399	},
400	{ 0 }
401};
402
403MODULE_DEVICE_TABLE(serio, serio_raw_serio_ids);
404
405static struct serio_driver serio_raw_drv = {
406	.driver		= {
407		.name	= "serio_raw",
408	},
409	.description	= DRIVER_DESC,
410	.id_table	= serio_raw_serio_ids,
411	.interrupt	= serio_raw_interrupt,
412	.connect	= serio_raw_connect,
413	.reconnect	= serio_raw_reconnect,
414	.disconnect	= serio_raw_disconnect,
415	.manual_bind	= true,
416};
417
418module_serio_driver(serio_raw_drv);