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, id: index);
66 if (aux_dev && !kref_get_unless_zero(kref: &aux_dev->refcount))
67 aux_dev = NULL;
68 mutex_unlock(lock: &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(error: -ENOMEM);
81 aux_dev->aux = aux;
82 atomic_set(v: &aux_dev->usecount, i: 1);
83 kref_init(kref: &aux_dev->refcount);
84
85 mutex_lock(&aux_idr_mutex);
86 index = idr_alloc(&aux_idr, ptr: aux_dev, start: 0, DRM_AUX_MINORS, GFP_KERNEL);
87 mutex_unlock(lock: &aux_idr_mutex);
88 if (index < 0) {
89 kfree(objp: aux_dev);
90 return ERR_PTR(error: 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(objp: 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, fmt: "%s\n", aux_dev->aux->name);
116 kref_put(kref: &aux_dev->refcount, release: 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(index: 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(v: &aux_dev->usecount))
153 return -ENODEV;
154
155 iov_iter_truncate(i: to, AUX_MAX_OFFSET - pos);
156
157 while (iov_iter_count(i: 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: aux_dev->aux, offset: pos, buffer: buf, size: todo);
167
168 if (res <= 0)
169 break;
170
171 if (copy_to_iter(addr: buf, bytes: res, i: 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(v: &aux_dev->usecount))
184 wake_up_var(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(v: &aux_dev->usecount))
196 return -ENODEV;
197
198 iov_iter_truncate(i: from, AUX_MAX_OFFSET - pos);
199
200 while (iov_iter_count(i: 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(addr: buf, bytes: todo, i: from)) {
210 res = -EFAULT;
211 break;
212 }
213
214 res = drm_dp_dpcd_write(aux: aux_dev->aux, offset: pos, buffer: buf, size: 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(v: &aux_dev->usecount))
227 wake_up_var(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(kref: &aux_dev->refcount, release: 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(lock: &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, id: aux_dev->index);
289 mutex_unlock(lock: &aux_idr_mutex);
290
291 atomic_dec(v: &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(cls: 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(kref: &aux_dev->refcount, release: 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(ptr: aux_dev))
310 return PTR_ERR(ptr: aux_dev);
311
312 aux_dev->dev = device_create(cls: drm_dp_aux_dev_class, parent: aux->dev,
313 MKDEV(drm_dev_major, aux_dev->index), NULL,
314 fmt: "drm_dp_aux%d", aux_dev->index);
315 if (IS_ERR(ptr: aux_dev->dev)) {
316 res = PTR_ERR(ptr: 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(name: "drm_dp_aux_dev");
334 if (IS_ERR(ptr: drm_dp_aux_dev_class)) {
335 return PTR_ERR(ptr: drm_dp_aux_dev_class);
336 }
337 drm_dp_aux_dev_class->dev_groups = drm_dp_aux_groups;
338
339 res = register_chrdev(major: 0, name: "aux", fops: &auxdev_fops);
340 if (res < 0)
341 goto out;
342 drm_dev_major = res;
343
344 return 0;
345out:
346 class_destroy(cls: drm_dp_aux_dev_class);
347 return res;
348}
349
350void drm_dp_aux_dev_exit(void)
351{
352 unregister_chrdev(major: drm_dev_major, name: "aux");
353 class_destroy(cls: drm_dp_aux_dev_class);
354}
355

source code of linux/drivers/gpu/drm/display/drm_dp_aux_dev.c