1 /* $NetBSD: drm_dp_aux_dev.c,v 1.3 2021/12/19 11:06:54 riastradh Exp $ */
2
3 /*
4 * Copyright © 2015 Intel Corporation
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a
7 * copy of this software and associated documentation files (the "Software"),
8 * to deal in the Software without restriction, including without limitation
9 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
10 * and/or sell copies of the Software, and to permit persons to whom the
11 * Software is furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice (including the next
14 * paragraph) shall be included in all copies or substantial portions of the
15 * Software.
16 *
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
20 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
21 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
22 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
23 * IN THE SOFTWARE.
24 *
25 * Authors:
26 * Rafael Antognolli <rafael.antognolli@intel.com>
27 *
28 */
29
30 #include <sys/cdefs.h>
31 __KERNEL_RCSID(0, "$NetBSD: drm_dp_aux_dev.c,v 1.3 2021/12/19 11:06:54 riastradh Exp $");
32
33 #include <linux/device.h>
34 #include <linux/fs.h>
35 #include <linux/init.h>
36 #include <linux/kernel.h>
37 #include <linux/module.h>
38 #include <linux/sched/signal.h>
39 #include <linux/slab.h>
40 #include <linux/uaccess.h>
41 #include <linux/uio.h>
42
43 #include <drm/drm_crtc.h>
44 #include <drm/drm_dp_helper.h>
45 #include <drm/drm_dp_mst_helper.h>
46 #include <drm/drm_print.h>
47
48 #include "drm_crtc_helper_internal.h"
49
50 struct drm_dp_aux_dev {
51 unsigned index;
52 struct drm_dp_aux *aux;
53 struct device *dev;
54 struct kref refcount;
55 atomic_t usecount;
56 };
57
58 #define DRM_AUX_MINORS 256
59 #define AUX_MAX_OFFSET (1 << 20)
60 static DEFINE_IDR(aux_idr);
61 static DEFINE_MUTEX(aux_idr_mutex);
62 static struct class *drm_dp_aux_dev_class;
63 static int drm_dev_major = -1;
64
drm_dp_aux_dev_get_by_minor(unsigned index)65 static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_minor(unsigned index)
66 {
67 struct drm_dp_aux_dev *aux_dev = NULL;
68
69 mutex_lock(&aux_idr_mutex);
70 aux_dev = idr_find(&aux_idr, index);
71 if (!kref_get_unless_zero(&aux_dev->refcount))
72 aux_dev = NULL;
73 mutex_unlock(&aux_idr_mutex);
74
75 return aux_dev;
76 }
77
alloc_drm_dp_aux_dev(struct drm_dp_aux * aux)78 static struct drm_dp_aux_dev *alloc_drm_dp_aux_dev(struct drm_dp_aux *aux)
79 {
80 struct drm_dp_aux_dev *aux_dev;
81 int index;
82
83 aux_dev = kzalloc(sizeof(*aux_dev), GFP_KERNEL);
84 if (!aux_dev)
85 return ERR_PTR(-ENOMEM);
86 aux_dev->aux = aux;
87 atomic_set(&aux_dev->usecount, 1);
88 kref_init(&aux_dev->refcount);
89
90 idr_preload(GFP_KERNEL);
91 mutex_lock(&aux_idr_mutex);
92 index = idr_alloc(&aux_idr, aux_dev, 0, DRM_AUX_MINORS, GFP_KERNEL);
93 mutex_unlock(&aux_idr_mutex);
94 idr_preload_end();
95 if (index < 0) {
96 kfree(aux_dev);
97 return ERR_PTR(index);
98 }
99 aux_dev->index = index;
100
101 return aux_dev;
102 }
103
release_drm_dp_aux_dev(struct kref * ref)104 static void release_drm_dp_aux_dev(struct kref *ref)
105 {
106 struct drm_dp_aux_dev *aux_dev =
107 container_of(ref, struct drm_dp_aux_dev, refcount);
108
109 kfree(aux_dev);
110 }
111
name_show(struct device * dev,struct device_attribute * attr,char * buf)112 static ssize_t name_show(struct device *dev,
113 struct device_attribute *attr, char *buf)
114 {
115 ssize_t res;
116 struct drm_dp_aux_dev *aux_dev =
117 drm_dp_aux_dev_get_by_minor(MINOR(dev->devt));
118
119 if (!aux_dev)
120 return -ENODEV;
121
122 res = sprintf(buf, "%s\n", aux_dev->aux->name);
123 kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
124
125 return res;
126 }
127 static DEVICE_ATTR_RO(name);
128
129 static struct attribute *drm_dp_aux_attrs[] = {
130 &dev_attr_name.attr,
131 NULL,
132 };
133 ATTRIBUTE_GROUPS(drm_dp_aux);
134
auxdev_open(struct inode * inode,struct file * file)135 static int auxdev_open(struct inode *inode, struct file *file)
136 {
137 unsigned int minor = iminor(inode);
138 struct drm_dp_aux_dev *aux_dev;
139
140 aux_dev = drm_dp_aux_dev_get_by_minor(minor);
141 if (!aux_dev)
142 return -ENODEV;
143
144 file->private_data = aux_dev;
145 return 0;
146 }
147
auxdev_llseek(struct file * file,loff_t offset,int whence)148 static loff_t auxdev_llseek(struct file *file, loff_t offset, int whence)
149 {
150 return fixed_size_llseek(file, offset, whence, AUX_MAX_OFFSET);
151 }
152
auxdev_read_iter(struct kiocb * iocb,struct iov_iter * to)153 static ssize_t auxdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
154 {
155 struct drm_dp_aux_dev *aux_dev = iocb->ki_filp->private_data;
156 loff_t pos = iocb->ki_pos;
157 ssize_t res = 0;
158
159 if (!atomic_inc_not_zero(&aux_dev->usecount))
160 return -ENODEV;
161
162 iov_iter_truncate(to, AUX_MAX_OFFSET - pos);
163
164 while (iov_iter_count(to)) {
165 uint8_t buf[DP_AUX_MAX_PAYLOAD_BYTES];
166 ssize_t todo = min(iov_iter_count(to), sizeof(buf));
167
168 if (signal_pending(current)) {
169 res = -ERESTARTSYS;
170 break;
171 }
172
173 res = drm_dp_dpcd_read(aux_dev->aux, pos, buf, todo);
174
175 if (res <= 0)
176 break;
177
178 if (copy_to_iter(buf, res, to) != res) {
179 res = -EFAULT;
180 break;
181 }
182
183 pos += res;
184 }
185
186 if (pos != iocb->ki_pos)
187 res = pos - iocb->ki_pos;
188 iocb->ki_pos = pos;
189
190 if (atomic_dec_and_test(&aux_dev->usecount))
191 wake_up_var(&aux_dev->usecount);
192
193 return res;
194 }
195
auxdev_write_iter(struct kiocb * iocb,struct iov_iter * from)196 static ssize_t auxdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
197 {
198 struct drm_dp_aux_dev *aux_dev = iocb->ki_filp->private_data;
199 loff_t pos = iocb->ki_pos;
200 ssize_t res = 0;
201
202 if (!atomic_inc_not_zero(&aux_dev->usecount))
203 return -ENODEV;
204
205 iov_iter_truncate(from, AUX_MAX_OFFSET - pos);
206
207 while (iov_iter_count(from)) {
208 uint8_t buf[DP_AUX_MAX_PAYLOAD_BYTES];
209 ssize_t todo = min(iov_iter_count(from), sizeof(buf));
210
211 if (signal_pending(current)) {
212 res = -ERESTARTSYS;
213 break;
214 }
215
216 if (!copy_from_iter_full(buf, todo, from)) {
217 res = -EFAULT;
218 break;
219 }
220
221 res = drm_dp_dpcd_write(aux_dev->aux, pos, buf, todo);
222
223 if (res <= 0)
224 break;
225
226 pos += res;
227 }
228
229 if (pos != iocb->ki_pos)
230 res = pos - iocb->ki_pos;
231 iocb->ki_pos = pos;
232
233 if (atomic_dec_and_test(&aux_dev->usecount))
234 wake_up_var(&aux_dev->usecount);
235
236 return res;
237 }
238
auxdev_release(struct inode * inode,struct file * file)239 static int auxdev_release(struct inode *inode, struct file *file)
240 {
241 struct drm_dp_aux_dev *aux_dev = file->private_data;
242
243 kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
244 return 0;
245 }
246
247 static const struct file_operations auxdev_fops = {
248 .owner = THIS_MODULE,
249 .llseek = auxdev_llseek,
250 .read_iter = auxdev_read_iter,
251 .write_iter = auxdev_write_iter,
252 .open = auxdev_open,
253 .release = auxdev_release,
254 };
255
256 #define to_auxdev(d) container_of(d, struct drm_dp_aux_dev, aux)
257
drm_dp_aux_dev_get_by_aux(struct drm_dp_aux * aux)258 static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_aux(struct drm_dp_aux *aux)
259 {
260 struct drm_dp_aux_dev *iter, *aux_dev = NULL;
261 int id;
262
263 /* don't increase kref count here because this function should only be
264 * used by drm_dp_aux_unregister_devnode. Thus, it will always have at
265 * least one reference - the one that drm_dp_aux_register_devnode
266 * created
267 */
268 mutex_lock(&aux_idr_mutex);
269 idr_for_each_entry(&aux_idr, iter, id) {
270 if (iter->aux == aux) {
271 aux_dev = iter;
272 break;
273 }
274 }
275 mutex_unlock(&aux_idr_mutex);
276 return aux_dev;
277 }
278
drm_dp_aux_unregister_devnode(struct drm_dp_aux * aux)279 void drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux)
280 {
281 struct drm_dp_aux_dev *aux_dev;
282 unsigned int minor;
283
284 aux_dev = drm_dp_aux_dev_get_by_aux(aux);
285 if (!aux_dev) /* attach must have failed */
286 return;
287
288 mutex_lock(&aux_idr_mutex);
289 idr_remove(&aux_idr, aux_dev->index);
290 mutex_unlock(&aux_idr_mutex);
291
292 atomic_dec(&aux_dev->usecount);
293 wait_var_event(&aux_dev->usecount, !atomic_read(&aux_dev->usecount));
294
295 minor = aux_dev->index;
296 if (aux_dev->dev)
297 device_destroy(drm_dp_aux_dev_class,
298 MKDEV(drm_dev_major, minor));
299
300 DRM_DEBUG("drm_dp_aux_dev: aux [%s] unregistering\n", aux->name);
301 kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
302 }
303
drm_dp_aux_register_devnode(struct drm_dp_aux * aux)304 int drm_dp_aux_register_devnode(struct drm_dp_aux *aux)
305 {
306 struct drm_dp_aux_dev *aux_dev;
307 int res;
308
309 aux_dev = alloc_drm_dp_aux_dev(aux);
310 if (IS_ERR(aux_dev))
311 return PTR_ERR(aux_dev);
312
313 aux_dev->dev = device_create(drm_dp_aux_dev_class, aux->dev,
314 MKDEV(drm_dev_major, aux_dev->index), NULL,
315 "drm_dp_aux%d", aux_dev->index);
316 if (IS_ERR(aux_dev->dev)) {
317 res = PTR_ERR(aux_dev->dev);
318 aux_dev->dev = NULL;
319 goto error;
320 }
321
322 DRM_DEBUG("drm_dp_aux_dev: aux [%s] registered as minor %d\n",
323 aux->name, aux_dev->index);
324 return 0;
325 error:
326 drm_dp_aux_unregister_devnode(aux);
327 return res;
328 }
329
drm_dp_aux_dev_init(void)330 int drm_dp_aux_dev_init(void)
331 {
332 int res;
333
334 drm_dp_aux_dev_class = class_create(THIS_MODULE, "drm_dp_aux_dev");
335 if (IS_ERR(drm_dp_aux_dev_class)) {
336 return PTR_ERR(drm_dp_aux_dev_class);
337 }
338 drm_dp_aux_dev_class->dev_groups = drm_dp_aux_groups;
339
340 res = register_chrdev(0, "aux", &auxdev_fops);
341 if (res < 0)
342 goto out;
343 drm_dev_major = res;
344
345 return 0;
346 out:
347 class_destroy(drm_dp_aux_dev_class);
348 return res;
349 }
350
drm_dp_aux_dev_exit(void)351 void drm_dp_aux_dev_exit(void)
352 {
353 unregister_chrdev(drm_dev_major, "aux");
354 class_destroy(drm_dp_aux_dev_class);
355 }
356