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 
45 struct 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)
55 static DEFINE_IDR(aux_idr);
56 static DEFINE_MUTEX(aux_idr_mutex);
57 static struct class *drm_dp_aux_dev_class;
58 static int drm_dev_major = -1;
59 
60 static 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 
73 static 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 
97 static 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 
105 static 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 }
120 static DEVICE_ATTR_RO(name);
121 
122 static struct attribute *drm_dp_aux_attrs[] = {
123 	&dev_attr_name.attr,
124 	NULL,
125 };
126 ATTRIBUTE_GROUPS(drm_dp_aux);
127 
128 static 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 
141 static 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 
146 static 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 
189 static 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 
232 static 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 
240 static 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 
251 static 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 
272 void 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 
303 int 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;
324 error:
325 	drm_dp_aux_unregister_devnode(aux);
326 	return res;
327 }
328 
329 int drm_dp_aux_dev_init(void)
330 {
331 	int res;
332 
333 	drm_dp_aux_dev_class = class_create(THIS_MODULE, "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;
345 out:
346 	class_destroy(drm_dp_aux_dev_class);
347 	return res;
348 }
349 
350 void drm_dp_aux_dev_exit(void)
351 {
352 	unregister_chrdev(drm_dev_major, "aux");
353 	class_destroy(drm_dp_aux_dev_class);
354 }
355