1/*
  2 * Copyright © 2015 Intel Corporation
  3 *
  4 * Permission is hereby granted, free of charge, to any person obtaining a
  5 * copy of this software and associated documentation files (the "Software"),
  6 * to deal in the Software without restriction, including without limitation
  7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  8 * and/or sell copies of the Software, and to permit persons to whom the
  9 * Software is furnished to do so, subject to the following conditions:
 10 *
 11 * The above copyright notice and this permission notice (including the next
 12 * paragraph) shall be included in all copies or substantial portions of the
 13 * Software.
 14 *
 15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 21 * IN THE SOFTWARE.
 22 *
 23 * Authors:
 24 *    Rafael Antognolli <rafael.antognolli@intel.com>
 25 *
 26 */
 27
 28#include <linux/device.h>
 29#include <linux/fs.h>
 30#include <linux/slab.h>
 31#include <linux/init.h>
 32#include <linux/kernel.h>
 33#include <linux/module.h>
 34#include <linux/uaccess.h>
 35#include <drm/drm_dp_helper.h>
 36#include <drm/drm_crtc.h>
 37#include <drm/drmP.h>
 38
 39#include "drm_crtc_helper_internal.h"
 40
 41struct drm_dp_aux_dev {
 42	unsigned index;
 43	struct drm_dp_aux *aux;
 44	struct device *dev;
 45	struct kref refcount;
 46	atomic_t usecount;
 47};
 48
 49#define DRM_AUX_MINORS	256
 50#define AUX_MAX_OFFSET	(1 << 20)
 51static DEFINE_IDR(aux_idr);
 52static DEFINE_MUTEX(aux_idr_mutex);
 53static struct class *drm_dp_aux_dev_class;
 54static int drm_dev_major = -1;
 55
 56static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_minor(unsigned index)
 57{
 58	struct drm_dp_aux_dev *aux_dev = NULL;
 59
 60	mutex_lock(&aux_idr_mutex);
 61	aux_dev = idr_find(&aux_idr, index);
 62	if (!kref_get_unless_zero(&aux_dev->refcount))
 63		aux_dev = NULL;
 64	mutex_unlock(&aux_idr_mutex);
 65
 66	return aux_dev;
 67}
 68
 69static struct drm_dp_aux_dev *alloc_drm_dp_aux_dev(struct drm_dp_aux *aux)
 70{
 71	struct drm_dp_aux_dev *aux_dev;
 72	int index;
 73
 74	aux_dev = kzalloc(sizeof(*aux_dev), GFP_KERNEL);
 75	if (!aux_dev)
 76		return ERR_PTR(-ENOMEM);
 77	aux_dev->aux = aux;
 78	atomic_set(&aux_dev->usecount, 1);
 79	kref_init(&aux_dev->refcount);
 80
 81	mutex_lock(&aux_idr_mutex);
 82	index = idr_alloc_cyclic(&aux_idr, aux_dev, 0, DRM_AUX_MINORS,
 83				 GFP_KERNEL);
 84	mutex_unlock(&aux_idr_mutex);
 85	if (index < 0) {
 86		kfree(aux_dev);
 87		return ERR_PTR(index);
 88	}
 89	aux_dev->index = index;
 90
 91	return aux_dev;
 92}
 93
 94static void release_drm_dp_aux_dev(struct kref *ref)
 95{
 96	struct drm_dp_aux_dev *aux_dev =
 97		container_of(ref, struct drm_dp_aux_dev, refcount);
 98
 99	kfree(aux_dev);
100}
101
102static ssize_t name_show(struct device *dev,
103			 struct device_attribute *attr, char *buf)
104{
105	ssize_t res;
106	struct drm_dp_aux_dev *aux_dev =
107		drm_dp_aux_dev_get_by_minor(MINOR(dev->devt));
108
109	if (!aux_dev)
110		return -ENODEV;
111
112	res = sprintf(buf, "%s\n", aux_dev->aux->name);
113	kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
114
115	return res;
116}
117static DEVICE_ATTR_RO(name);
118
119static struct attribute *drm_dp_aux_attrs[] = {
120	&dev_attr_name.attr,
121	NULL,
122};
123ATTRIBUTE_GROUPS(drm_dp_aux);
124
125static int auxdev_open(struct inode *inode, struct file *file)
126{
127	unsigned int minor = iminor(inode);
128	struct drm_dp_aux_dev *aux_dev;
129
130	aux_dev = drm_dp_aux_dev_get_by_minor(minor);
131	if (!aux_dev)
132		return -ENODEV;
133
134	file->private_data = aux_dev;
135	return 0;
136}
137
138static loff_t auxdev_llseek(struct file *file, loff_t offset, int whence)
139{
140	return fixed_size_llseek(file, offset, whence, AUX_MAX_OFFSET);
141}
142
143static ssize_t auxdev_read(struct file *file, char __user *buf, size_t count,
144			   loff_t *offset)
145{
146	size_t bytes_pending, num_bytes_processed = 0;
147	struct drm_dp_aux_dev *aux_dev = file->private_data;
148	ssize_t res = 0;
149
150	if (!atomic_inc_not_zero(&aux_dev->usecount))
151		return -ENODEV;
152
153	bytes_pending = min((loff_t)count, AUX_MAX_OFFSET - (*offset));
154
155	if (!access_ok(VERIFY_WRITE, buf, bytes_pending)) {
156		res = -EFAULT;
157		goto out;
158	}
159
160	while (bytes_pending > 0) {
161		uint8_t localbuf[DP_AUX_MAX_PAYLOAD_BYTES];
162		ssize_t todo = min_t(size_t, bytes_pending, sizeof(localbuf));
163
164		if (signal_pending(current)) {
165			res = num_bytes_processed ?
166				num_bytes_processed : -ERESTARTSYS;
167			goto out;
168		}
169
170		res = drm_dp_dpcd_read(aux_dev->aux, *offset, localbuf, todo);
171		if (res <= 0) {
172			res = num_bytes_processed ? num_bytes_processed : res;
173			goto out;
174		}
175		if (__copy_to_user(buf + num_bytes_processed, localbuf, res)) {
176			res = num_bytes_processed ?
177				num_bytes_processed : -EFAULT;
178			goto out;
179		}
180		bytes_pending -= res;
181		*offset += res;
182		num_bytes_processed += res;
183		res = num_bytes_processed;
184	}
185
186out:
187	atomic_dec(&aux_dev->usecount);
188	wake_up_atomic_t(&aux_dev->usecount);
189	return res;
190}
191
192static ssize_t auxdev_write(struct file *file, const char __user *buf,
193			    size_t count, loff_t *offset)
194{
195	size_t bytes_pending, num_bytes_processed = 0;
196	struct drm_dp_aux_dev *aux_dev = file->private_data;
197	ssize_t res = 0;
198
199	if (!atomic_inc_not_zero(&aux_dev->usecount))
200		return -ENODEV;
201
202	bytes_pending = min((loff_t)count, AUX_MAX_OFFSET - *offset);
203
204	if (!access_ok(VERIFY_READ, buf, bytes_pending)) {
205		res = -EFAULT;
206		goto out;
207	}
208
209	while (bytes_pending > 0) {
210		uint8_t localbuf[DP_AUX_MAX_PAYLOAD_BYTES];
211		ssize_t todo = min_t(size_t, bytes_pending, sizeof(localbuf));
212
213		if (signal_pending(current)) {
214			res = num_bytes_processed ?
215				num_bytes_processed : -ERESTARTSYS;
216			goto out;
217		}
218
219		if (__copy_from_user(localbuf,
220				     buf + num_bytes_processed, todo)) {
221			res = num_bytes_processed ?
222				num_bytes_processed : -EFAULT;
223			goto out;
224		}
225
226		res = drm_dp_dpcd_write(aux_dev->aux, *offset, localbuf, todo);
227		if (res <= 0) {
228			res = num_bytes_processed ? num_bytes_processed : res;
229			goto out;
230		}
231		bytes_pending -= res;
232		*offset += res;
233		num_bytes_processed += res;
234		res = num_bytes_processed;
235	}
236
237out:
238	atomic_dec(&aux_dev->usecount);
239	wake_up_atomic_t(&aux_dev->usecount);
240	return res;
241}
242
243static int auxdev_release(struct inode *inode, struct file *file)
244{
245	struct drm_dp_aux_dev *aux_dev = file->private_data;
246
247	kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
248	return 0;
249}
250
251static const struct file_operations auxdev_fops = {
252	.owner		= THIS_MODULE,
253	.llseek		= auxdev_llseek,
254	.read		= auxdev_read,
255	.write		= auxdev_write,
256	.open		= auxdev_open,
257	.release	= auxdev_release,
258};
259
260#define to_auxdev(d) container_of(d, struct drm_dp_aux_dev, aux)
261
262static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_aux(struct drm_dp_aux *aux)
263{
264	struct drm_dp_aux_dev *iter, *aux_dev = NULL;
265	int id;
266
267	/* don't increase kref count here because this function should only be
268	 * used by drm_dp_aux_unregister_devnode. Thus, it will always have at
269	 * least one reference - the one that drm_dp_aux_register_devnode
270	 * created
271	 */
272	mutex_lock(&aux_idr_mutex);
273	idr_for_each_entry(&aux_idr, iter, id) {
274		if (iter->aux == aux) {
275			aux_dev = iter;
276			break;
277		}
278	}
279	mutex_unlock(&aux_idr_mutex);
280	return aux_dev;
281}
282
283static int auxdev_wait_atomic_t(atomic_t *p)
284{
285	schedule();
286	return 0;
287}
288
289void drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux)
290{
291	struct drm_dp_aux_dev *aux_dev;
292	unsigned int minor;
293
294	aux_dev = drm_dp_aux_dev_get_by_aux(aux);
295	if (!aux_dev) /* attach must have failed */
296		return;
297
298	mutex_lock(&aux_idr_mutex);
299	idr_remove(&aux_idr, aux_dev->index);
300	mutex_unlock(&aux_idr_mutex);
301
302	atomic_dec(&aux_dev->usecount);
303	wait_on_atomic_t(&aux_dev->usecount, auxdev_wait_atomic_t,
304			 TASK_UNINTERRUPTIBLE);
305
306	minor = aux_dev->index;
307	if (aux_dev->dev)
308		device_destroy(drm_dp_aux_dev_class,
309			       MKDEV(drm_dev_major, minor));
310
311	DRM_DEBUG("drm_dp_aux_dev: aux [%s] unregistering\n", aux->name);
312	kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
313}
314
315int drm_dp_aux_register_devnode(struct drm_dp_aux *aux)
316{
317	struct drm_dp_aux_dev *aux_dev;
318	int res;
319
320	aux_dev = alloc_drm_dp_aux_dev(aux);
321	if (IS_ERR(aux_dev))
322		return PTR_ERR(aux_dev);
323
324	aux_dev->dev = device_create(drm_dp_aux_dev_class, aux->dev,
325				     MKDEV(drm_dev_major, aux_dev->index), NULL,
326				     "drm_dp_aux%d", aux_dev->index);
327	if (IS_ERR(aux_dev->dev)) {
328		res = PTR_ERR(aux_dev->dev);
329		aux_dev->dev = NULL;
330		goto error;
331	}
332
333	DRM_DEBUG("drm_dp_aux_dev: aux [%s] registered as minor %d\n",
334		  aux->name, aux_dev->index);
335	return 0;
336error:
337	drm_dp_aux_unregister_devnode(aux);
338	return res;
339}
340
341int drm_dp_aux_dev_init(void)
342{
343	int res;
344
345	drm_dp_aux_dev_class = class_create(THIS_MODULE, "drm_dp_aux_dev");
346	if (IS_ERR(drm_dp_aux_dev_class)) {
347		return PTR_ERR(drm_dp_aux_dev_class);
348	}
349	drm_dp_aux_dev_class->dev_groups = drm_dp_aux_groups;
350
351	res = register_chrdev(0, "aux", &auxdev_fops);
352	if (res < 0)
353		goto out;
354	drm_dev_major = res;
355
356	return 0;
357out:
358	class_destroy(drm_dp_aux_dev_class);
359	return res;
360}
361
362void drm_dp_aux_dev_exit(void)
363{
364	unregister_chrdev(drm_dev_major, "aux");
365	class_destroy(drm_dp_aux_dev_class);
366}