1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Roccat driver for Linux
4 *
5 * Copyright (c) 2010 Stefan Achatz <erazor_de@users.sourceforge.net>
6 */
7
8/*
9 */
10
11/*
12 * Module roccat is a char device used to report special events of roccat
13 * hardware to userland. These events include requests for on-screen-display of
14 * profile or dpi settings or requests for execution of macro sequences that are
15 * not stored in device. The information in these events depends on hid device
16 * implementation and contains data that is not available in a single hid event
17 * or else hidraw could have been used.
18 * It is inspired by hidraw, but uses only one circular buffer for all readers.
19 */
20
21#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
22
23#include <linux/cdev.h>
24#include <linux/poll.h>
25#include <linux/sched/signal.h>
26#include <linux/hid-roccat.h>
27#include <linux/module.h>
28
29#define ROCCAT_FIRST_MINOR 0
30#define ROCCAT_MAX_DEVICES 8
31
32/* should be a power of 2 for performance reason */
33#define ROCCAT_CBUF_SIZE 16
34
35struct roccat_report {
36	uint8_t *value;
37};
38
39struct roccat_device {
40	unsigned int minor;
41	int report_size;
42	int open;
43	int exist;
44	wait_queue_head_t wait;
45	struct device *dev;
46	struct hid_device *hid;
47	struct list_head readers;
48	/* protects modifications of readers list */
49	struct mutex readers_lock;
50
51	/*
52	 * circular_buffer has one writer and multiple readers with their own
53	 * read pointers
54	 */
55	struct roccat_report cbuf[ROCCAT_CBUF_SIZE];
56	int cbuf_end;
57	struct mutex cbuf_lock;
58};
59
60struct roccat_reader {
61	struct list_head node;
62	struct roccat_device *device;
63	int cbuf_start;
64};
65
66static int roccat_major;
67static struct cdev roccat_cdev;
68
69static struct roccat_device *devices[ROCCAT_MAX_DEVICES];
70/* protects modifications of devices array */
71static DEFINE_MUTEX(devices_lock);
72
73static ssize_t roccat_read(struct file *file, char __user *buffer,
74		size_t count, loff_t *ppos)
75{
76	struct roccat_reader *reader = file->private_data;
77	struct roccat_device *device = reader->device;
78	struct roccat_report *report;
79	ssize_t retval = 0, len;
80	DECLARE_WAITQUEUE(wait, current);
81
82	mutex_lock(&device->cbuf_lock);
83
84	/* no data? */
85	if (reader->cbuf_start == device->cbuf_end) {
86		add_wait_queue(&device->wait, &wait);
87		set_current_state(TASK_INTERRUPTIBLE);
88
89		/* wait for data */
90		while (reader->cbuf_start == device->cbuf_end) {
91			if (file->f_flags & O_NONBLOCK) {
92				retval = -EAGAIN;
93				break;
94			}
95			if (signal_pending(current)) {
96				retval = -ERESTARTSYS;
97				break;
98			}
99			if (!device->exist) {
100				retval = -EIO;
101				break;
102			}
103
104			mutex_unlock(&device->cbuf_lock);
105			schedule();
106			mutex_lock(&device->cbuf_lock);
107			set_current_state(TASK_INTERRUPTIBLE);
108		}
109
110		set_current_state(TASK_RUNNING);
111		remove_wait_queue(&device->wait, &wait);
112	}
113
114	/* here we either have data or a reason to return if retval is set */
115	if (retval)
116		goto exit_unlock;
117
118	report = &device->cbuf[reader->cbuf_start];
119	/*
120	 * If report is larger than requested amount of data, rest of report
121	 * is lost!
122	 */
123	len = device->report_size > count ? count : device->report_size;
124
125	if (copy_to_user(buffer, report->value, len)) {
126		retval = -EFAULT;
127		goto exit_unlock;
128	}
129	retval += len;
130	reader->cbuf_start = (reader->cbuf_start + 1) % ROCCAT_CBUF_SIZE;
131
132exit_unlock:
133	mutex_unlock(&device->cbuf_lock);
134	return retval;
135}
136
137static __poll_t roccat_poll(struct file *file, poll_table *wait)
138{
139	struct roccat_reader *reader = file->private_data;
140	poll_wait(file, &reader->device->wait, wait);
141	if (reader->cbuf_start != reader->device->cbuf_end)
142		return EPOLLIN | EPOLLRDNORM;
143	if (!reader->device->exist)
144		return EPOLLERR | EPOLLHUP;
145	return 0;
146}
147
148static int roccat_open(struct inode *inode, struct file *file)
149{
150	unsigned int minor = iminor(inode);
151	struct roccat_reader *reader;
152	struct roccat_device *device;
153	int error = 0;
154
155	reader = kzalloc(sizeof(struct roccat_reader), GFP_KERNEL);
156	if (!reader)
157		return -ENOMEM;
158
159	mutex_lock(&devices_lock);
160
161	device = devices[minor];
162
163	if (!device) {
164		pr_emerg("roccat device with minor %d doesn't exist\n", minor);
165		error = -ENODEV;
166		goto exit_err_devices;
167	}
168
169	mutex_lock(&device->readers_lock);
170
171	if (!device->open++) {
172		/* power on device on adding first reader */
173		error = hid_hw_power(device->hid, PM_HINT_FULLON);
174		if (error < 0) {
175			--device->open;
176			goto exit_err_readers;
177		}
178
179		error = hid_hw_open(device->hid);
180		if (error < 0) {
181			hid_hw_power(device->hid, PM_HINT_NORMAL);
182			--device->open;
183			goto exit_err_readers;
184		}
185	}
186
187	reader->device = device;
188	/* new reader doesn't get old events */
189	reader->cbuf_start = device->cbuf_end;
190
191	list_add_tail(&reader->node, &device->readers);
192	file->private_data = reader;
193
194exit_err_readers:
195	mutex_unlock(&device->readers_lock);
196exit_err_devices:
197	mutex_unlock(&devices_lock);
198	if (error)
199		kfree(reader);
200	return error;
201}
202
203static int roccat_release(struct inode *inode, struct file *file)
204{
205	unsigned int minor = iminor(inode);
206	struct roccat_reader *reader = file->private_data;
207	struct roccat_device *device;
208
209	mutex_lock(&devices_lock);
210
211	device = devices[minor];
212	if (!device) {
213		mutex_unlock(&devices_lock);
214		pr_emerg("roccat device with minor %d doesn't exist\n", minor);
215		return -ENODEV;
216	}
217
218	mutex_lock(&device->readers_lock);
219	list_del(&reader->node);
220	mutex_unlock(&device->readers_lock);
221	kfree(reader);
222
223	if (!--device->open) {
224		/* removing last reader */
225		if (device->exist) {
226			hid_hw_power(device->hid, PM_HINT_NORMAL);
227			hid_hw_close(device->hid);
228		} else {
229			kfree(device);
230		}
231	}
232
233	mutex_unlock(&devices_lock);
234
235	return 0;
236}
237
238/*
239 * roccat_report_event() - output data to readers
240 * @minor: minor device number returned by roccat_connect()
241 * @data: pointer to data
242 *
243 * Return value is zero on success, a negative error code on failure.
244 *
245 * This is called from interrupt handler.
246 */
247int roccat_report_event(int minor, u8 const *data)
248{
249	struct roccat_device *device;
250	struct roccat_reader *reader;
251	struct roccat_report *report;
252	uint8_t *new_value;
253
254	device = devices[minor];
255
256	new_value = kmemdup(data, device->report_size, GFP_ATOMIC);
257	if (!new_value)
258		return -ENOMEM;
259
260	report = &device->cbuf[device->cbuf_end];
261
262	/* passing NULL is safe */
263	kfree(report->value);
264
265	report->value = new_value;
266	device->cbuf_end = (device->cbuf_end + 1) % ROCCAT_CBUF_SIZE;
267
268	list_for_each_entry(reader, &device->readers, node) {
269		/*
270		 * As we already inserted one element, the buffer can't be
271		 * empty. If start and end are equal, buffer is full and we
272		 * increase start, so that slow reader misses one event, but
273		 * gets the newer ones in the right order.
274		 */
275		if (reader->cbuf_start == device->cbuf_end)
276			reader->cbuf_start = (reader->cbuf_start + 1) % ROCCAT_CBUF_SIZE;
277	}
278
279	wake_up_interruptible(&device->wait);
280	return 0;
281}
282EXPORT_SYMBOL_GPL(roccat_report_event);
283
284/*
285 * roccat_connect() - create a char device for special event output
286 * @class: the class thats used to create the device. Meant to hold device
287 * specific sysfs attributes.
288 * @hid: the hid device the char device should be connected to.
289 * @report_size: size of reports
290 *
291 * Return value is minor device number in Range [0, ROCCAT_MAX_DEVICES] on
292 * success, a negative error code on failure.
293 */
294int roccat_connect(struct class *klass, struct hid_device *hid, int report_size)
295{
296	unsigned int minor;
297	struct roccat_device *device;
298	int temp;
299
300	device = kzalloc(sizeof(struct roccat_device), GFP_KERNEL);
301	if (!device)
302		return -ENOMEM;
303
304	mutex_lock(&devices_lock);
305
306	for (minor = 0; minor < ROCCAT_MAX_DEVICES; ++minor) {
307		if (devices[minor])
308			continue;
309		break;
310	}
311
312	if (minor < ROCCAT_MAX_DEVICES) {
313		devices[minor] = device;
314	} else {
315		mutex_unlock(&devices_lock);
316		kfree(device);
317		return -EINVAL;
318	}
319
320	device->dev = device_create(klass, &hid->dev,
321			MKDEV(roccat_major, minor), NULL,
322			"%s%s%d", "roccat", hid->driver->name, minor);
323
324	if (IS_ERR(device->dev)) {
325		devices[minor] = NULL;
326		mutex_unlock(&devices_lock);
327		temp = PTR_ERR(device->dev);
328		kfree(device);
329		return temp;
330	}
331
332	mutex_unlock(&devices_lock);
333
334	init_waitqueue_head(&device->wait);
335	INIT_LIST_HEAD(&device->readers);
336	mutex_init(&device->readers_lock);
337	mutex_init(&device->cbuf_lock);
338	device->minor = minor;
339	device->hid = hid;
340	device->exist = 1;
341	device->cbuf_end = 0;
342	device->report_size = report_size;
343
344	return minor;
345}
346EXPORT_SYMBOL_GPL(roccat_connect);
347
348/* roccat_disconnect() - remove char device from hid device
349 * @minor: the minor device number returned by roccat_connect()
350 */
351void roccat_disconnect(int minor)
352{
353	struct roccat_device *device;
354
355	mutex_lock(&devices_lock);
356	device = devices[minor];
357	mutex_unlock(&devices_lock);
358
359	device->exist = 0; /* TODO exist maybe not needed */
360
361	device_destroy(device->dev->class, MKDEV(roccat_major, minor));
362
363	mutex_lock(&devices_lock);
364	devices[minor] = NULL;
365	mutex_unlock(&devices_lock);
366
367	if (device->open) {
368		hid_hw_close(device->hid);
369		wake_up_interruptible(&device->wait);
370	} else {
371		kfree(device);
372	}
373}
374EXPORT_SYMBOL_GPL(roccat_disconnect);
375
376static long roccat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
377{
378	struct inode *inode = file_inode(file);
379	struct roccat_device *device;
380	unsigned int minor = iminor(inode);
381	long retval = 0;
382
383	mutex_lock(&devices_lock);
384
385	device = devices[minor];
386	if (!device) {
387		retval = -ENODEV;
388		goto out;
389	}
390
391	switch (cmd) {
392	case ROCCATIOCGREPSIZE:
393		if (put_user(device->report_size, (int __user *)arg))
394			retval = -EFAULT;
395		break;
396	default:
397		retval = -ENOTTY;
398	}
399out:
400	mutex_unlock(&devices_lock);
401	return retval;
402}
403
404static const struct file_operations roccat_ops = {
405	.owner = THIS_MODULE,
406	.read = roccat_read,
407	.poll = roccat_poll,
408	.open = roccat_open,
409	.release = roccat_release,
410	.llseek = noop_llseek,
411	.unlocked_ioctl = roccat_ioctl,
412};
413
414static int __init roccat_init(void)
415{
416	int retval;
417	dev_t dev_id;
418
419	retval = alloc_chrdev_region(&dev_id, ROCCAT_FIRST_MINOR,
420			ROCCAT_MAX_DEVICES, "roccat");
421	if (retval < 0) {
422		pr_warn("can't get major number\n");
423		goto error;
424	}
425
426	roccat_major = MAJOR(dev_id);
427
428	cdev_init(&roccat_cdev, &roccat_ops);
429	retval = cdev_add(&roccat_cdev, dev_id, ROCCAT_MAX_DEVICES);
430
431	if (retval < 0) {
432		pr_warn("cannot add cdev\n");
433		goto cleanup_alloc_chrdev_region;
434	}
435	return 0;
436
437
438 cleanup_alloc_chrdev_region:
439	unregister_chrdev_region(dev_id, ROCCAT_MAX_DEVICES);
440 error:
441	return retval;
442}
443
444static void __exit roccat_exit(void)
445{
446	dev_t dev_id = MKDEV(roccat_major, 0);
447
448	cdev_del(&roccat_cdev);
449	unregister_chrdev_region(dev_id, ROCCAT_MAX_DEVICES);
450}
451
452module_init(roccat_init);
453module_exit(roccat_exit);
454
455MODULE_AUTHOR("Stefan Achatz");
456MODULE_DESCRIPTION("USB Roccat char device");
457MODULE_LICENSE("GPL v2");
458