xref: /netbsd-src/sys/external/bsd/drm2/dist/drm/drm_dp_aux_dev.c (revision 0d58057b114de0f5e3f2a4e610a63c75eefa358a)
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