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 <linux/uio.h>
 36#include <drm/drm_dp_helper.h>
 37#include <drm/drm_crtc.h>
 38#include <drm/drmP.h>
 39
 40#include "drm_crtc_helper_internal.h"
 41
 42struct drm_dp_aux_dev {
 43	unsigned index;
 44	struct drm_dp_aux *aux;
 45	struct device *dev;
 46	struct kref refcount;
 47	atomic_t usecount;
 48};
 49
 50#define DRM_AUX_MINORS	256
 51#define AUX_MAX_OFFSET	(1 << 20)
 52static DEFINE_IDR(aux_idr);
 53static DEFINE_MUTEX(aux_idr_mutex);
 54static struct class *drm_dp_aux_dev_class;
 55static int drm_dev_major = -1;
 56
 57static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_minor(unsigned index)
 58{
 59	struct drm_dp_aux_dev *aux_dev = NULL;
 60
 61	mutex_lock(&aux_idr_mutex);
 62	aux_dev = idr_find(&aux_idr, index);
 63	if (!kref_get_unless_zero(&aux_dev->refcount))
 64		aux_dev = NULL;
 65	mutex_unlock(&aux_idr_mutex);
 66
 67	return aux_dev;
 68}
 69
 70static struct drm_dp_aux_dev *alloc_drm_dp_aux_dev(struct drm_dp_aux *aux)
 71{
 72	struct drm_dp_aux_dev *aux_dev;
 73	int index;
 74
 75	aux_dev = kzalloc(sizeof(*aux_dev), GFP_KERNEL);
 76	if (!aux_dev)
 77		return ERR_PTR(-ENOMEM);
 78	aux_dev->aux = aux;
 79	atomic_set(&aux_dev->usecount, 1);
 80	kref_init(&aux_dev->refcount);
 81
 82	mutex_lock(&aux_idr_mutex);
 83	index = idr_alloc_cyclic(&aux_idr, aux_dev, 0, DRM_AUX_MINORS,
 84				 GFP_KERNEL);
 85	mutex_unlock(&aux_idr_mutex);
 86	if (index < 0) {
 87		kfree(aux_dev);
 88		return ERR_PTR(index);
 89	}
 90	aux_dev->index = index;
 91
 92	return aux_dev;
 93}
 94
 95static void release_drm_dp_aux_dev(struct kref *ref)
 96{
 97	struct drm_dp_aux_dev *aux_dev =
 98		container_of(ref, struct drm_dp_aux_dev, refcount);
 99
100	kfree(aux_dev);
101}
102
103static ssize_t name_show(struct device *dev,
104			 struct device_attribute *attr, char *buf)
105{
106	ssize_t res;
107	struct drm_dp_aux_dev *aux_dev =
108		drm_dp_aux_dev_get_by_minor(MINOR(dev->devt));
109
110	if (!aux_dev)
111		return -ENODEV;
112
113	res = sprintf(buf, "%s\n", aux_dev->aux->name);
114	kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
115
116	return res;
117}
118static DEVICE_ATTR_RO(name);
119
120static struct attribute *drm_dp_aux_attrs[] = {
121	&dev_attr_name.attr,
122	NULL,
123};
124ATTRIBUTE_GROUPS(drm_dp_aux);
125
126static int auxdev_open(struct inode *inode, struct file *file)
127{
128	unsigned int minor = iminor(inode);
129	struct drm_dp_aux_dev *aux_dev;
130
131	aux_dev = drm_dp_aux_dev_get_by_minor(minor);
132	if (!aux_dev)
133		return -ENODEV;
134
135	file->private_data = aux_dev;
136	return 0;
137}
138
139static loff_t auxdev_llseek(struct file *file, loff_t offset, int whence)
140{
141	return fixed_size_llseek(file, offset, whence, AUX_MAX_OFFSET);
142}
143
144static ssize_t auxdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
145{
146	struct drm_dp_aux_dev *aux_dev = iocb->ki_filp->private_data;
147	loff_t pos = iocb->ki_pos;
148	ssize_t res = 0;
149
150	if (!atomic_inc_not_zero(&aux_dev->usecount))
151		return -ENODEV;
152
153	iov_iter_truncate(to, AUX_MAX_OFFSET - pos);
154
155	while (iov_iter_count(to)) {
156		uint8_t buf[DP_AUX_MAX_PAYLOAD_BYTES];
157		ssize_t todo = min(iov_iter_count(to), sizeof(buf));
158
159		if (signal_pending(current)) {
160			res = -ERESTARTSYS;
161			break;
162		}
163
164		res = drm_dp_dpcd_read(aux_dev->aux, pos, buf, todo);
165		if (res <= 0)
166			break;
167
168		if (copy_to_iter(buf, res, to) != res) {
169			res = -EFAULT;
170			break;
171		}
172
173		pos += res;
174	}
175
176	if (pos != iocb->ki_pos)
177		res = pos - iocb->ki_pos;
178	iocb->ki_pos = pos;
179
180	if (atomic_dec_and_test(&aux_dev->usecount))
181		wake_up_var(&aux_dev->usecount);
182
183	return res;
184}
185
186static ssize_t auxdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
187{
188	struct drm_dp_aux_dev *aux_dev = iocb->ki_filp->private_data;
189	loff_t pos = iocb->ki_pos;
190	ssize_t res = 0;
191
192	if (!atomic_inc_not_zero(&aux_dev->usecount))
193		return -ENODEV;
194
195	iov_iter_truncate(from, AUX_MAX_OFFSET - pos);
196
197	while (iov_iter_count(from)) {
198		uint8_t buf[DP_AUX_MAX_PAYLOAD_BYTES];
199		ssize_t todo = min(iov_iter_count(from), sizeof(buf));
200
201		if (signal_pending(current)) {
202			res = -ERESTARTSYS;
203			break;
204		}
205
206		if (!copy_from_iter_full(buf, todo, from)) {
207			res = -EFAULT;
208			break;
209		}
210
211		res = drm_dp_dpcd_write(aux_dev->aux, pos, buf, todo);
212		if (res <= 0)
213			break;
214
215		pos += res;
216	}
217
218	if (pos != iocb->ki_pos)
219		res = pos - iocb->ki_pos;
220	iocb->ki_pos = pos;
221
222	if (atomic_dec_and_test(&aux_dev->usecount))
223		wake_up_var(&aux_dev->usecount);
224
225	return res;
226}
227
228static int auxdev_release(struct inode *inode, struct file *file)
229{
230	struct drm_dp_aux_dev *aux_dev = file->private_data;
231
232	kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
233	return 0;
234}
235
236static const struct file_operations auxdev_fops = {
237	.owner		= THIS_MODULE,
238	.llseek		= auxdev_llseek,
239	.read_iter	= auxdev_read_iter,
240	.write_iter	= auxdev_write_iter,
241	.open		= auxdev_open,
242	.release	= auxdev_release,
243};
244
245#define to_auxdev(d) container_of(d, struct drm_dp_aux_dev, aux)
246
247static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_aux(struct drm_dp_aux *aux)
248{
249	struct drm_dp_aux_dev *iter, *aux_dev = NULL;
250	int id;
251
252	/* don't increase kref count here because this function should only be
253	 * used by drm_dp_aux_unregister_devnode. Thus, it will always have at
254	 * least one reference - the one that drm_dp_aux_register_devnode
255	 * created
256	 */
257	mutex_lock(&aux_idr_mutex);
258	idr_for_each_entry(&aux_idr, iter, id) {
259		if (iter->aux == aux) {
260			aux_dev = iter;
261			break;
262		}
263	}
264	mutex_unlock(&aux_idr_mutex);
265	return aux_dev;
266}
267
268void drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux)
269{
270	struct drm_dp_aux_dev *aux_dev;
271	unsigned int minor;
272
273	aux_dev = drm_dp_aux_dev_get_by_aux(aux);
274	if (!aux_dev) /* attach must have failed */
275		return;
276
277	mutex_lock(&aux_idr_mutex);
278	idr_remove(&aux_idr, aux_dev->index);
279	mutex_unlock(&aux_idr_mutex);
280
281	atomic_dec(&aux_dev->usecount);
282	wait_var_event(&aux_dev->usecount, !atomic_read(&aux_dev->usecount));
283
284	minor = aux_dev->index;
285	if (aux_dev->dev)
286		device_destroy(drm_dp_aux_dev_class,
287			       MKDEV(drm_dev_major, minor));
288
289	DRM_DEBUG("drm_dp_aux_dev: aux [%s] unregistering\n", aux->name);
290	kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
291}
292
293int drm_dp_aux_register_devnode(struct drm_dp_aux *aux)
294{
295	struct drm_dp_aux_dev *aux_dev;
296	int res;
297
298	aux_dev = alloc_drm_dp_aux_dev(aux);
299	if (IS_ERR(aux_dev))
300		return PTR_ERR(aux_dev);
301
302	aux_dev->dev = device_create(drm_dp_aux_dev_class, aux->dev,
303				     MKDEV(drm_dev_major, aux_dev->index), NULL,
304				     "drm_dp_aux%d", aux_dev->index);
305	if (IS_ERR(aux_dev->dev)) {
306		res = PTR_ERR(aux_dev->dev);
307		aux_dev->dev = NULL;
308		goto error;
309	}
310
311	DRM_DEBUG("drm_dp_aux_dev: aux [%s] registered as minor %d\n",
312		  aux->name, aux_dev->index);
313	return 0;
314error:
315	drm_dp_aux_unregister_devnode(aux);
316	return res;
317}
318
319int drm_dp_aux_dev_init(void)
320{
321	int res;
322
323	drm_dp_aux_dev_class = class_create(THIS_MODULE, "drm_dp_aux_dev");
324	if (IS_ERR(drm_dp_aux_dev_class)) {
325		return PTR_ERR(drm_dp_aux_dev_class);
326	}
327	drm_dp_aux_dev_class->dev_groups = drm_dp_aux_groups;
328
329	res = register_chrdev(0, "aux", &auxdev_fops);
330	if (res < 0)
331		goto out;
332	drm_dev_major = res;
333
334	return 0;
335out:
336	class_destroy(drm_dp_aux_dev_class);
337	return res;
338}
339
340void drm_dp_aux_dev_exit(void)
341{
342	unregister_chrdev(drm_dev_major, "aux");
343	class_destroy(drm_dp_aux_dev_class);
344}