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
42 struct 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)
52 static DEFINE_IDR(aux_idr);
53 static DEFINE_MUTEX(aux_idr_mutex);
54 static struct class *drm_dp_aux_dev_class;
55 static int drm_dev_major = -1;
56
drm_dp_aux_dev_get_by_minor(unsigned index)57 static 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
alloc_drm_dp_aux_dev(struct drm_dp_aux * aux)70 static 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
release_drm_dp_aux_dev(struct kref * ref)95 static 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
name_show(struct device * dev,struct device_attribute * attr,char * buf)103 static 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 }
118 static DEVICE_ATTR_RO(name);
119
120 static struct attribute *drm_dp_aux_attrs[] = {
121 &dev_attr_name.attr,
122 NULL,
123 };
124 ATTRIBUTE_GROUPS(drm_dp_aux);
125
auxdev_open(struct inode * inode,struct file * file)126 static 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
auxdev_llseek(struct file * file,loff_t offset,int whence)139 static 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
auxdev_read_iter(struct kiocb * iocb,struct iov_iter * to)144 static 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 atomic_dec(&aux_dev->usecount);
181 wake_up_atomic_t(&aux_dev->usecount);
182 return res;
183 }
184
auxdev_write_iter(struct kiocb * iocb,struct iov_iter * from)185 static ssize_t auxdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
186 {
187 struct drm_dp_aux_dev *aux_dev = iocb->ki_filp->private_data;
188 loff_t pos = iocb->ki_pos;
189 ssize_t res = 0;
190
191 if (!atomic_inc_not_zero(&aux_dev->usecount))
192 return -ENODEV;
193
194 iov_iter_truncate(from, AUX_MAX_OFFSET - pos);
195
196 while (iov_iter_count(from)) {
197 uint8_t buf[DP_AUX_MAX_PAYLOAD_BYTES];
198 ssize_t todo = min(iov_iter_count(from), sizeof(buf));
199
200 if (signal_pending(current)) {
201 res = -ERESTARTSYS;
202 break;
203 }
204
205 if (!copy_from_iter_full(buf, todo, from)) {
206 res = -EFAULT;
207 break;
208 }
209
210 res = drm_dp_dpcd_write(aux_dev->aux, pos, buf, todo);
211 if (res <= 0)
212 break;
213
214 pos += res;
215 }
216
217 if (pos != iocb->ki_pos)
218 res = pos - iocb->ki_pos;
219 iocb->ki_pos = pos;
220
221 atomic_dec(&aux_dev->usecount);
222 wake_up_atomic_t(&aux_dev->usecount);
223 return res;
224 }
225
auxdev_release(struct inode * inode,struct file * file)226 static int auxdev_release(struct inode *inode, struct file *file)
227 {
228 struct drm_dp_aux_dev *aux_dev = file->private_data;
229
230 kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
231 return 0;
232 }
233
234 static const struct file_operations auxdev_fops = {
235 .owner = THIS_MODULE,
236 .llseek = auxdev_llseek,
237 .read_iter = auxdev_read_iter,
238 .write_iter = auxdev_write_iter,
239 .open = auxdev_open,
240 .release = auxdev_release,
241 };
242
243 #define to_auxdev(d) container_of(d, struct drm_dp_aux_dev, aux)
244
drm_dp_aux_dev_get_by_aux(struct drm_dp_aux * aux)245 static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_aux(struct drm_dp_aux *aux)
246 {
247 struct drm_dp_aux_dev *iter, *aux_dev = NULL;
248 int id;
249
250 /* don't increase kref count here because this function should only be
251 * used by drm_dp_aux_unregister_devnode. Thus, it will always have at
252 * least one reference - the one that drm_dp_aux_register_devnode
253 * created
254 */
255 mutex_lock(&aux_idr_mutex);
256 idr_for_each_entry(&aux_idr, iter, id) {
257 if (iter->aux == aux) {
258 aux_dev = iter;
259 break;
260 }
261 }
262 mutex_unlock(&aux_idr_mutex);
263 return aux_dev;
264 }
265
auxdev_wait_atomic_t(atomic_t * p)266 static int auxdev_wait_atomic_t(atomic_t *p)
267 {
268 schedule();
269 return 0;
270 }
271
drm_dp_aux_unregister_devnode(struct drm_dp_aux * aux)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 mutex_lock(&aux_idr_mutex);
282 idr_remove(&aux_idr, aux_dev->index);
283 mutex_unlock(&aux_idr_mutex);
284
285 atomic_dec(&aux_dev->usecount);
286 wait_on_atomic_t(&aux_dev->usecount, auxdev_wait_atomic_t,
287 TASK_UNINTERRUPTIBLE);
288
289 minor = aux_dev->index;
290 if (aux_dev->dev)
291 device_destroy(drm_dp_aux_dev_class,
292 MKDEV(drm_dev_major, minor));
293
294 DRM_DEBUG("drm_dp_aux_dev: aux [%s] unregistering\n", aux->name);
295 kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
296 }
297
drm_dp_aux_register_devnode(struct drm_dp_aux * aux)298 int drm_dp_aux_register_devnode(struct drm_dp_aux *aux)
299 {
300 struct drm_dp_aux_dev *aux_dev;
301 int res;
302
303 aux_dev = alloc_drm_dp_aux_dev(aux);
304 if (IS_ERR(aux_dev))
305 return PTR_ERR(aux_dev);
306
307 aux_dev->dev = device_create(drm_dp_aux_dev_class, aux->dev,
308 MKDEV(drm_dev_major, aux_dev->index), NULL,
309 "drm_dp_aux%d", aux_dev->index);
310 if (IS_ERR(aux_dev->dev)) {
311 res = PTR_ERR(aux_dev->dev);
312 aux_dev->dev = NULL;
313 goto error;
314 }
315
316 DRM_DEBUG("drm_dp_aux_dev: aux [%s] registered as minor %d\n",
317 aux->name, aux_dev->index);
318 return 0;
319 error:
320 drm_dp_aux_unregister_devnode(aux);
321 return res;
322 }
323
drm_dp_aux_dev_init(void)324 int drm_dp_aux_dev_init(void)
325 {
326 int res;
327
328 drm_dp_aux_dev_class = class_create(THIS_MODULE, "drm_dp_aux_dev");
329 if (IS_ERR(drm_dp_aux_dev_class)) {
330 return PTR_ERR(drm_dp_aux_dev_class);
331 }
332 drm_dp_aux_dev_class->dev_groups = drm_dp_aux_groups;
333
334 res = register_chrdev(0, "aux", &auxdev_fops);
335 if (res < 0)
336 goto out;
337 drm_dev_major = res;
338
339 return 0;
340 out:
341 class_destroy(drm_dp_aux_dev_class);
342 return res;
343 }
344
drm_dp_aux_dev_exit(void)345 void drm_dp_aux_dev_exit(void)
346 {
347 unregister_chrdev(drm_dev_major, "aux");
348 class_destroy(drm_dp_aux_dev_class);
349 }
350