hid-roccat.c

  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	mutex_lock(&device->readers_lock);
261	mutex_lock(&device->cbuf_lock);
262
263	report = &device->cbuf[device->cbuf_end];
264
265	/* passing NULL is safe */
266	kfree(report->value);
267
268	report->value = new_value;
269	device->cbuf_end = (device->cbuf_end + 1) % ROCCAT_CBUF_SIZE;
270
271	list_for_each_entry(reader, &device->readers, node) {
272		/*
273		 * As we already inserted one element, the buffer can't be
274		 * empty. If start and end are equal, buffer is full and we
275		 * increase start, so that slow reader misses one event, but
276		 * gets the newer ones in the right order.
277		 */
278		if (reader->cbuf_start == device->cbuf_end)
279			reader->cbuf_start = (reader->cbuf_start + 1) % ROCCAT_CBUF_SIZE;
280	}
281
282	mutex_unlock(&device->cbuf_lock);
283	mutex_unlock(&device->readers_lock);
284
285	wake_up_interruptible(&device->wait);
286	return 0;
287}
288EXPORT_SYMBOL_GPL(roccat_report_event);
289
290/*
291 * roccat_connect() - create a char device for special event output
292 * @class: the class thats used to create the device. Meant to hold device
293 * specific sysfs attributes.
294 * @hid: the hid device the char device should be connected to.
295 * @report_size: size of reports
296 *
297 * Return value is minor device number in Range [0, ROCCAT_MAX_DEVICES] on
298 * success, a negative error code on failure.
299 */
300int roccat_connect(const struct class *klass, struct hid_device *hid, int report_size)
301{
302	unsigned int minor;
303	struct roccat_device *device;
304	int temp;
305
306	device = kzalloc(sizeof(struct roccat_device), GFP_KERNEL);
307	if (!device)
308		return -ENOMEM;
309
310	mutex_lock(&devices_lock);
311
312	for (minor = 0; minor < ROCCAT_MAX_DEVICES; ++minor) {
313		if (devices[minor])
314			continue;
315		break;
316	}
317
318	if (minor < ROCCAT_MAX_DEVICES) {
319		devices[minor] = device;
320	} else {
321		mutex_unlock(&devices_lock);
322		kfree(device);
323		return -EINVAL;
324	}
325
326	device->dev = device_create(klass, &hid->dev,
327			MKDEV(roccat_major, minor), NULL,
328			"%s%s%d", "roccat", hid->driver->name, minor);
329
330	if (IS_ERR(device->dev)) {
331		devices[minor] = NULL;
332		mutex_unlock(&devices_lock);
333		temp = PTR_ERR(device->dev);
334		kfree(device);
335		return temp;
336	}
337
338	mutex_unlock(&devices_lock);
339
340	init_waitqueue_head(&device->wait);
341	INIT_LIST_HEAD(&device->readers);
342	mutex_init(&device->readers_lock);
343	mutex_init(&device->cbuf_lock);
344	device->minor = minor;
345	device->hid = hid;
346	device->exist = 1;
347	device->cbuf_end = 0;
348	device->report_size = report_size;
349
350	return minor;
351}
352EXPORT_SYMBOL_GPL(roccat_connect);
353
354/* roccat_disconnect() - remove char device from hid device
355 * @minor: the minor device number returned by roccat_connect()
356 */
357void roccat_disconnect(int minor)
358{
359	struct roccat_device *device;
360
361	mutex_lock(&devices_lock);
362	device = devices[minor];
363	mutex_unlock(&devices_lock);
364
365	device->exist = 0; /* TODO exist maybe not needed */
366
367	device_destroy(device->dev->class, MKDEV(roccat_major, minor));
368
369	mutex_lock(&devices_lock);
370	devices[minor] = NULL;
371	mutex_unlock(&devices_lock);
372
373	if (device->open) {
374		hid_hw_close(device->hid);
375		wake_up_interruptible(&device->wait);
376	} else {
377		kfree(device);
378	}
379}
380EXPORT_SYMBOL_GPL(roccat_disconnect);
381
382static long roccat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
383{
384	struct inode *inode = file_inode(file);
385	struct roccat_device *device;
386	unsigned int minor = iminor(inode);
387	long retval = 0;
388
389	mutex_lock(&devices_lock);
390
391	device = devices[minor];
392	if (!device) {
393		retval = -ENODEV;
394		goto out;
395	}
396
397	switch (cmd) {
398	case ROCCATIOCGREPSIZE:
399		if (put_user(device->report_size, (int __user *)arg))
400			retval = -EFAULT;
401		break;
402	default:
403		retval = -ENOTTY;
404	}
405out:
406	mutex_unlock(&devices_lock);
407	return retval;
408}
409
410static const struct file_operations roccat_ops = {
411	.owner = THIS_MODULE,
412	.read = roccat_read,
413	.poll = roccat_poll,
414	.open = roccat_open,
415	.release = roccat_release,
416	.llseek = noop_llseek,
417	.unlocked_ioctl = roccat_ioctl,
418};
419
420static int __init roccat_init(void)
421{
422	int retval;
423	dev_t dev_id;
424
425	retval = alloc_chrdev_region(&dev_id, ROCCAT_FIRST_MINOR,
426			ROCCAT_MAX_DEVICES, "roccat");
427	if (retval < 0) {
428		pr_warn("can't get major number\n");
429		goto error;
430	}
431
432	roccat_major = MAJOR(dev_id);
433
434	cdev_init(&roccat_cdev, &roccat_ops);
435	retval = cdev_add(&roccat_cdev, dev_id, ROCCAT_MAX_DEVICES);
436
437	if (retval < 0) {
438		pr_warn("cannot add cdev\n");
439		goto cleanup_alloc_chrdev_region;
440	}
441	return 0;
442
443
444 cleanup_alloc_chrdev_region:
445	unregister_chrdev_region(dev_id, ROCCAT_MAX_DEVICES);
446 error:
447	return retval;
448}
449
450static void __exit roccat_exit(void)
451{
452	dev_t dev_id = MKDEV(roccat_major, 0);
453
454	cdev_del(&roccat_cdev);
455	unregister_chrdev_region(dev_id, ROCCAT_MAX_DEVICES);
456}
457
458module_init(roccat_init);
459module_exit(roccat_exit);
460
461MODULE_AUTHOR("Stefan Achatz");
462MODULE_DESCRIPTION("USB Roccat char device");
463MODULE_LICENSE("GPL v2");