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/init.h>
31#include <linux/kernel.h>
32#include <linux/module.h>
33#include <linux/sched/signal.h>
34#include <linux/slab.h>
35#include <linux/uaccess.h>
36#include <linux/uio.h>
37
38#include <drm/display/drm_dp_helper.h>
39#include <drm/display/drm_dp_mst_helper.h>
40#include <drm/drm_crtc.h>
41#include <drm/drm_print.h>
42
43#include "drm_dp_helper_internal.h"
44
45struct drm_dp_aux_dev {
46	unsigned index;
47	struct drm_dp_aux *aux;
48	struct device *dev;
49	struct kref refcount;
50	atomic_t usecount;
51};
52
53#define DRM_AUX_MINORS	256
54#define AUX_MAX_OFFSET	(1 << 20)
55static DEFINE_IDR(aux_idr);
56static DEFINE_MUTEX(aux_idr_mutex);
57static struct class *drm_dp_aux_dev_class;
58static int drm_dev_major = -1;
59
60static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_minor(unsigned index)
61{
62	struct drm_dp_aux_dev *aux_dev = NULL;
63
64	mutex_lock(&aux_idr_mutex);
65	aux_dev = idr_find(&aux_idr, index);
66	if (aux_dev && !kref_get_unless_zero(&aux_dev->refcount))
67		aux_dev = NULL;
68	mutex_unlock(&aux_idr_mutex);
69
70	return aux_dev;
71}
72
73static struct drm_dp_aux_dev *alloc_drm_dp_aux_dev(struct drm_dp_aux *aux)
74{
75	struct drm_dp_aux_dev *aux_dev;
76	int index;
77
78	aux_dev = kzalloc(sizeof(*aux_dev), GFP_KERNEL);
79	if (!aux_dev)
80		return ERR_PTR(-ENOMEM);
81	aux_dev->aux = aux;
82	atomic_set(&aux_dev->usecount, 1);
83	kref_init(&aux_dev->refcount);
84
85	mutex_lock(&aux_idr_mutex);
86	index = idr_alloc(&aux_idr, aux_dev, 0, DRM_AUX_MINORS, GFP_KERNEL);
87	mutex_unlock(&aux_idr_mutex);
88	if (index < 0) {
89		kfree(aux_dev);
90		return ERR_PTR(index);
91	}
92	aux_dev->index = index;
93
94	return aux_dev;
95}
96
97static void release_drm_dp_aux_dev(struct kref *ref)
98{
99	struct drm_dp_aux_dev *aux_dev =
100		container_of(ref, struct drm_dp_aux_dev, refcount);
101
102	kfree(aux_dev);
103}
104
105static ssize_t name_show(struct device *dev,
106			 struct device_attribute *attr, char *buf)
107{
108	ssize_t res;
109	struct drm_dp_aux_dev *aux_dev =
110		drm_dp_aux_dev_get_by_minor(MINOR(dev->devt));
111
112	if (!aux_dev)
113		return -ENODEV;
114
115	res = sprintf(buf, "%s\n", aux_dev->aux->name);
116	kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
117
118	return res;
119}
120static DEVICE_ATTR_RO(name);
121
122static struct attribute *drm_dp_aux_attrs[] = {
123	&dev_attr_name.attr,
124	NULL,
125};
126ATTRIBUTE_GROUPS(drm_dp_aux);
127
128static int auxdev_open(struct inode *inode, struct file *file)
129{
130	unsigned int minor = iminor(inode);
131	struct drm_dp_aux_dev *aux_dev;
132
133	aux_dev = drm_dp_aux_dev_get_by_minor(minor);
134	if (!aux_dev)
135		return -ENODEV;
136
137	file->private_data = aux_dev;
138	return 0;
139}
140
141static loff_t auxdev_llseek(struct file *file, loff_t offset, int whence)
142{
143	return fixed_size_llseek(file, offset, whence, AUX_MAX_OFFSET);
144}
145
146static ssize_t auxdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
147{
148	struct drm_dp_aux_dev *aux_dev = iocb->ki_filp->private_data;
149	loff_t pos = iocb->ki_pos;
150	ssize_t res = 0;
151
152	if (!atomic_inc_not_zero(&aux_dev->usecount))
153		return -ENODEV;
154
155	iov_iter_truncate(to, AUX_MAX_OFFSET - pos);
156
157	while (iov_iter_count(to)) {
158		uint8_t buf[DP_AUX_MAX_PAYLOAD_BYTES];
159		ssize_t todo = min(iov_iter_count(to), sizeof(buf));
160
161		if (signal_pending(current)) {
162			res = -ERESTARTSYS;
163			break;
164		}
165
166		res = drm_dp_dpcd_read(aux_dev->aux, pos, buf, todo);
167
168		if (res <= 0)
169			break;
170
171		if (copy_to_iter(buf, res, to) != res) {
172			res = -EFAULT;
173			break;
174		}
175
176		pos += res;
177	}
178
179	if (pos != iocb->ki_pos)
180		res = pos - iocb->ki_pos;
181	iocb->ki_pos = pos;
182
183	if (atomic_dec_and_test(&aux_dev->usecount))
184		wake_up_var(&aux_dev->usecount);
185
186	return res;
187}
188
189static ssize_t auxdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
190{
191	struct drm_dp_aux_dev *aux_dev = iocb->ki_filp->private_data;
192	loff_t pos = iocb->ki_pos;
193	ssize_t res = 0;
194
195	if (!atomic_inc_not_zero(&aux_dev->usecount))
196		return -ENODEV;
197
198	iov_iter_truncate(from, AUX_MAX_OFFSET - pos);
199
200	while (iov_iter_count(from)) {
201		uint8_t buf[DP_AUX_MAX_PAYLOAD_BYTES];
202		ssize_t todo = min(iov_iter_count(from), sizeof(buf));
203
204		if (signal_pending(current)) {
205			res = -ERESTARTSYS;
206			break;
207		}
208
209		if (!copy_from_iter_full(buf, todo, from)) {
210			res = -EFAULT;
211			break;
212		}
213
214		res = drm_dp_dpcd_write(aux_dev->aux, pos, buf, todo);
215
216		if (res <= 0)
217			break;
218
219		pos += res;
220	}
221
222	if (pos != iocb->ki_pos)
223		res = pos - iocb->ki_pos;
224	iocb->ki_pos = pos;
225
226	if (atomic_dec_and_test(&aux_dev->usecount))
227		wake_up_var(&aux_dev->usecount);
228
229	return res;
230}
231
232static int auxdev_release(struct inode *inode, struct file *file)
233{
234	struct drm_dp_aux_dev *aux_dev = file->private_data;
235
236	kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
237	return 0;
238}
239
240static const struct file_operations auxdev_fops = {
241	.owner		= THIS_MODULE,
242	.llseek		= auxdev_llseek,
243	.read_iter	= auxdev_read_iter,
244	.write_iter	= auxdev_write_iter,
245	.open		= auxdev_open,
246	.release	= auxdev_release,
247};
248
249#define to_auxdev(d) container_of(d, struct drm_dp_aux_dev, aux)
250
251static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_aux(struct drm_dp_aux *aux)
252{
253	struct drm_dp_aux_dev *iter, *aux_dev = NULL;
254	int id;
255
256	/* don't increase kref count here because this function should only be
257	 * used by drm_dp_aux_unregister_devnode. Thus, it will always have at
258	 * least one reference - the one that drm_dp_aux_register_devnode
259	 * created
260	 */
261	mutex_lock(&aux_idr_mutex);
262	idr_for_each_entry(&aux_idr, iter, id) {
263		if (iter->aux == aux) {
264			aux_dev = iter;
265			break;
266		}
267	}
268	mutex_unlock(&aux_idr_mutex);
269	return aux_dev;
270}
271
272void drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux)
273{
274	struct drm_dp_aux_dev *aux_dev;
275	unsigned int minor;
276
277	aux_dev = drm_dp_aux_dev_get_by_aux(aux);
278	if (!aux_dev) /* attach must have failed */
279		return;
280
281	/*
282	 * As some AUX adapters may exist as platform devices which outlive their respective DRM
283	 * devices, we clear drm_dev to ensure that we never accidentally reference a stale pointer
284	 */
285	aux->drm_dev = NULL;
286
287	mutex_lock(&aux_idr_mutex);
288	idr_remove(&aux_idr, aux_dev->index);
289	mutex_unlock(&aux_idr_mutex);
290
291	atomic_dec(&aux_dev->usecount);
292	wait_var_event(&aux_dev->usecount, !atomic_read(&aux_dev->usecount));
293
294	minor = aux_dev->index;
295	if (aux_dev->dev)
296		device_destroy(drm_dp_aux_dev_class,
297			       MKDEV(drm_dev_major, minor));
298
299	DRM_DEBUG("drm_dp_aux_dev: aux [%s] unregistering\n", aux->name);
300	kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
301}
302
303int drm_dp_aux_register_devnode(struct drm_dp_aux *aux)
304{
305	struct drm_dp_aux_dev *aux_dev;
306	int res;
307
308	aux_dev = alloc_drm_dp_aux_dev(aux);
309	if (IS_ERR(aux_dev))
310		return PTR_ERR(aux_dev);
311
312	aux_dev->dev = device_create(drm_dp_aux_dev_class, aux->dev,
313				     MKDEV(drm_dev_major, aux_dev->index), NULL,
314				     "drm_dp_aux%d", aux_dev->index);
315	if (IS_ERR(aux_dev->dev)) {
316		res = PTR_ERR(aux_dev->dev);
317		aux_dev->dev = NULL;
318		goto error;
319	}
320
321	DRM_DEBUG("drm_dp_aux_dev: aux [%s] registered as minor %d\n",
322		  aux->name, aux_dev->index);
323	return 0;
324error:
325	drm_dp_aux_unregister_devnode(aux);
326	return res;
327}
328
329int drm_dp_aux_dev_init(void)
330{
331	int res;
332
333	drm_dp_aux_dev_class = class_create("drm_dp_aux_dev");
334	if (IS_ERR(drm_dp_aux_dev_class)) {
335		return PTR_ERR(drm_dp_aux_dev_class);
336	}
337	drm_dp_aux_dev_class->dev_groups = drm_dp_aux_groups;
338
339	res = register_chrdev(0, "aux", &auxdev_fops);
340	if (res < 0)
341		goto out;
342	drm_dev_major = res;
343
344	return 0;
345out:
346	class_destroy(drm_dp_aux_dev_class);
347	return res;
348}
349
350void drm_dp_aux_dev_exit(void)
351{
352	unregister_chrdev(drm_dev_major, "aux");
353	class_destroy(drm_dp_aux_dev_class);
354}
355