xref: /linux/drivers/platform/chrome/cros_ec_chardev.c (revision 02680c23d7b3febe45ea3d4f9818c2b2dc89020a) 
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Miscellaneous character driver for ChromeOS Embedded Controller
4  *
5  * Copyright 2014 Google, Inc.
6  * Copyright 2019 Google LLC
7  *
8  * This file is a rework and part of the code is ported from
9  * drivers/mfd/cros_ec_dev.c that was originally written by
10  * Bill Richardson.
11  */
12 
13 #include <linux/init.h>
14 #include <linux/device.h>
15 #include <linux/fs.h>
16 #include <linux/miscdevice.h>
17 #include <linux/module.h>
18 #include <linux/notifier.h>
19 #include <linux/platform_data/cros_ec_chardev.h>
20 #include <linux/platform_data/cros_ec_commands.h>
21 #include <linux/platform_data/cros_ec_proto.h>
22 #include <linux/platform_device.h>
23 #include <linux/poll.h>
24 #include <linux/slab.h>
25 #include <linux/types.h>
26 #include <linux/uaccess.h>
27 
28 #define DRV_NAME		"cros-ec-chardev"
29 
30 /* Arbitrary bounded size for the event queue */
31 #define CROS_MAX_EVENT_LEN	PAGE_SIZE
32 
33 struct chardev_data {
34 	struct cros_ec_dev *ec_dev;
35 	struct miscdevice misc;
36 };
37 
38 struct chardev_priv {
39 	struct cros_ec_dev *ec_dev;
40 	struct notifier_block notifier;
41 	wait_queue_head_t wait_event;
42 	unsigned long event_mask;
43 	struct list_head events;
44 	size_t event_len;
45 };
46 
47 struct ec_event {
48 	struct list_head node;
49 	size_t size;
50 	u8 event_type;
51 	u8 data[];
52 };
53 
54 static int ec_get_version(struct cros_ec_dev *ec, char *str, int maxlen)
55 {
56 	static const char * const current_image_name[] = {
57 		"unknown", "read-only", "read-write", "invalid",
58 	};
59 	struct ec_response_get_version *resp;
60 	struct cros_ec_command *msg;
61 	int ret;
62 
63 	msg = kzalloc(sizeof(*msg) + sizeof(*resp), GFP_KERNEL);
64 	if (!msg)
65 		return -ENOMEM;
66 
67 	msg->command = EC_CMD_GET_VERSION + ec->cmd_offset;
68 	msg->insize = sizeof(*resp);
69 
70 	ret = cros_ec_cmd_xfer_status(ec->ec_dev, msg);
71 	if (ret < 0) {
72 		snprintf(str, maxlen,
73 			 "Unknown EC version, returned error: %d\n",
74 			 msg->result);
75 		goto exit;
76 	}
77 
78 	resp = (struct ec_response_get_version *)msg->data;
79 	if (resp->current_image >= ARRAY_SIZE(current_image_name))
80 		resp->current_image = 3; /* invalid */
81 
82 	snprintf(str, maxlen, "%s\n%s\n%s\n%s\n", CROS_EC_DEV_VERSION,
83 		 resp->version_string_ro, resp->version_string_rw,
84 		 current_image_name[resp->current_image]);
85 
86 	ret = 0;
87 exit:
88 	kfree(msg);
89 	return ret;
90 }
91 
92 static int cros_ec_chardev_mkbp_event(struct notifier_block *nb,
93 				      unsigned long queued_during_suspend,
94 				      void *_notify)
95 {
96 	struct chardev_priv *priv = container_of(nb, struct chardev_priv,
97 						 notifier);
98 	struct cros_ec_device *ec_dev = priv->ec_dev->ec_dev;
99 	struct ec_event *event;
100 	unsigned long event_bit = 1 << ec_dev->event_data.event_type;
101 	int total_size = sizeof(*event) + ec_dev->event_size;
102 
103 	if (!(event_bit & priv->event_mask) ||
104 	    (priv->event_len + total_size) > CROS_MAX_EVENT_LEN)
105 		return NOTIFY_DONE;
106 
107 	event = kzalloc(total_size, GFP_KERNEL);
108 	if (!event)
109 		return NOTIFY_DONE;
110 
111 	event->size = ec_dev->event_size;
112 	event->event_type = ec_dev->event_data.event_type;
113 	memcpy(event->data, &ec_dev->event_data.data, ec_dev->event_size);
114 
115 	spin_lock(&priv->wait_event.lock);
116 	list_add_tail(&event->node, &priv->events);
117 	priv->event_len += total_size;
118 	wake_up_locked(&priv->wait_event);
119 	spin_unlock(&priv->wait_event.lock);
120 
121 	return NOTIFY_OK;
122 }
123 
124 static struct ec_event *cros_ec_chardev_fetch_event(struct chardev_priv *priv,
125 						    bool fetch, bool block)
126 {
127 	struct ec_event *event;
128 	int err;
129 
130 	spin_lock(&priv->wait_event.lock);
131 	if (!block && list_empty(&priv->events)) {
132 		event = ERR_PTR(-EWOULDBLOCK);
133 		goto out;
134 	}
135 
136 	if (!fetch) {
137 		event = NULL;
138 		goto out;
139 	}
140 
141 	err = wait_event_interruptible_locked(priv->wait_event,
142 					      !list_empty(&priv->events));
143 	if (err) {
144 		event = ERR_PTR(err);
145 		goto out;
146 	}
147 
148 	event = list_first_entry(&priv->events, struct ec_event, node);
149 	list_del(&event->node);
150 	priv->event_len -= sizeof(*event) + event->size;
151 
152 out:
153 	spin_unlock(&priv->wait_event.lock);
154 	return event;
155 }
156 
157 /*
158  * Device file ops
159  */
160 static int cros_ec_chardev_open(struct inode *inode, struct file *filp)
161 {
162 	struct miscdevice *mdev = filp->private_data;
163 	struct cros_ec_dev *ec_dev = dev_get_drvdata(mdev->parent);
164 	struct chardev_priv *priv;
165 	int ret;
166 
167 	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
168 	if (!priv)
169 		return -ENOMEM;
170 
171 	priv->ec_dev = ec_dev;
172 	filp->private_data = priv;
173 	INIT_LIST_HEAD(&priv->events);
174 	init_waitqueue_head(&priv->wait_event);
175 	nonseekable_open(inode, filp);
176 
177 	priv->notifier.notifier_call = cros_ec_chardev_mkbp_event;
178 	ret = blocking_notifier_chain_register(&ec_dev->ec_dev->event_notifier,
179 					       &priv->notifier);
180 	if (ret) {
181 		dev_err(ec_dev->dev, "failed to register event notifier\n");
182 		kfree(priv);
183 	}
184 
185 	return ret;
186 }
187 
188 static __poll_t cros_ec_chardev_poll(struct file *filp, poll_table *wait)
189 {
190 	struct chardev_priv *priv = filp->private_data;
191 
192 	poll_wait(filp, &priv->wait_event, wait);
193 
194 	if (list_empty(&priv->events))
195 		return 0;
196 
197 	return EPOLLIN | EPOLLRDNORM;
198 }
199 
200 static ssize_t cros_ec_chardev_read(struct file *filp, char __user *buffer,
201 				     size_t length, loff_t *offset)
202 {
203 	char msg[sizeof(struct ec_response_get_version) +
204 		 sizeof(CROS_EC_DEV_VERSION)];
205 	struct chardev_priv *priv = filp->private_data;
206 	struct cros_ec_dev *ec_dev = priv->ec_dev;
207 	size_t count;
208 	int ret;
209 
210 	if (priv->event_mask) { /* queued MKBP event */
211 		struct ec_event *event;
212 
213 		event = cros_ec_chardev_fetch_event(priv, length != 0,
214 						!(filp->f_flags & O_NONBLOCK));
215 		if (IS_ERR(event))
216 			return PTR_ERR(event);
217 		/*
218 		 * length == 0 is special - no IO is done but we check
219 		 * for error conditions.
220 		 */
221 		if (length == 0)
222 			return 0;
223 
224 		/* The event is 1 byte of type plus the payload */
225 		count = min(length, event->size + 1);
226 		ret = copy_to_user(buffer, &event->event_type, count);
227 		kfree(event);
228 		if (ret) /* the copy failed */
229 			return -EFAULT;
230 		*offset = count;
231 		return count;
232 	}
233 
234 	/*
235 	 * Legacy behavior if no event mask is defined
236 	 */
237 	if (*offset != 0)
238 		return 0;
239 
240 	ret = ec_get_version(ec_dev, msg, sizeof(msg));
241 	if (ret)
242 		return ret;
243 
244 	count = min(length, strlen(msg));
245 
246 	if (copy_to_user(buffer, msg, count))
247 		return -EFAULT;
248 
249 	*offset = count;
250 	return count;
251 }
252 
253 static int cros_ec_chardev_release(struct inode *inode, struct file *filp)
254 {
255 	struct chardev_priv *priv = filp->private_data;
256 	struct cros_ec_dev *ec_dev = priv->ec_dev;
257 	struct ec_event *event, *e;
258 
259 	blocking_notifier_chain_unregister(&ec_dev->ec_dev->event_notifier,
260 					   &priv->notifier);
261 
262 	list_for_each_entry_safe(event, e, &priv->events, node) {
263 		list_del(&event->node);
264 		kfree(event);
265 	}
266 	kfree(priv);
267 
268 	return 0;
269 }
270 
271 /*
272  * Ioctls
273  */
274 static long cros_ec_chardev_ioctl_xcmd(struct cros_ec_dev *ec, void __user *arg)
275 {
276 	struct cros_ec_command *s_cmd;
277 	struct cros_ec_command u_cmd;
278 	long ret;
279 
280 	if (copy_from_user(&u_cmd, arg, sizeof(u_cmd)))
281 		return -EFAULT;
282 
283 	if (u_cmd.outsize > EC_MAX_MSG_BYTES ||
284 	    u_cmd.insize > EC_MAX_MSG_BYTES)
285 		return -EINVAL;
286 
287 	s_cmd = kmalloc(sizeof(*s_cmd) + max(u_cmd.outsize, u_cmd.insize),
288 			GFP_KERNEL);
289 	if (!s_cmd)
290 		return -ENOMEM;
291 
292 	if (copy_from_user(s_cmd, arg, sizeof(*s_cmd) + u_cmd.outsize)) {
293 		ret = -EFAULT;
294 		goto exit;
295 	}
296 
297 	if (u_cmd.outsize != s_cmd->outsize ||
298 	    u_cmd.insize != s_cmd->insize) {
299 		ret = -EINVAL;
300 		goto exit;
301 	}
302 
303 	s_cmd->command += ec->cmd_offset;
304 	ret = cros_ec_cmd_xfer_status(ec->ec_dev, s_cmd);
305 	/* Only copy data to userland if data was received. */
306 	if (ret < 0)
307 		goto exit;
308 
309 	if (copy_to_user(arg, s_cmd, sizeof(*s_cmd) + s_cmd->insize))
310 		ret = -EFAULT;
311 exit:
312 	kfree(s_cmd);
313 	return ret;
314 }
315 
316 static long cros_ec_chardev_ioctl_readmem(struct cros_ec_dev *ec,
317 					   void __user *arg)
318 {
319 	struct cros_ec_device *ec_dev = ec->ec_dev;
320 	struct cros_ec_readmem s_mem = { };
321 	long num;
322 
323 	/* Not every platform supports direct reads */
324 	if (!ec_dev->cmd_readmem)
325 		return -ENOTTY;
326 
327 	if (copy_from_user(&s_mem, arg, sizeof(s_mem)))
328 		return -EFAULT;
329 
330 	num = ec_dev->cmd_readmem(ec_dev, s_mem.offset, s_mem.bytes,
331 				  s_mem.buffer);
332 	if (num <= 0)
333 		return num;
334 
335 	if (copy_to_user((void __user *)arg, &s_mem, sizeof(s_mem)))
336 		return -EFAULT;
337 
338 	return num;
339 }
340 
341 static long cros_ec_chardev_ioctl(struct file *filp, unsigned int cmd,
342 				   unsigned long arg)
343 {
344 	struct chardev_priv *priv = filp->private_data;
345 	struct cros_ec_dev *ec = priv->ec_dev;
346 
347 	if (_IOC_TYPE(cmd) != CROS_EC_DEV_IOC)
348 		return -ENOTTY;
349 
350 	switch (cmd) {
351 	case CROS_EC_DEV_IOCXCMD:
352 		return cros_ec_chardev_ioctl_xcmd(ec, (void __user *)arg);
353 	case CROS_EC_DEV_IOCRDMEM:
354 		return cros_ec_chardev_ioctl_readmem(ec, (void __user *)arg);
355 	case CROS_EC_DEV_IOCEVENTMASK:
356 		priv->event_mask = arg;
357 		return 0;
358 	}
359 
360 	return -ENOTTY;
361 }
362 
363 static const struct file_operations chardev_fops = {
364 	.open		= cros_ec_chardev_open,
365 	.poll		= cros_ec_chardev_poll,
366 	.read		= cros_ec_chardev_read,
367 	.release	= cros_ec_chardev_release,
368 	.unlocked_ioctl	= cros_ec_chardev_ioctl,
369 #ifdef CONFIG_COMPAT
370 	.compat_ioctl	= cros_ec_chardev_ioctl,
371 #endif
372 };
373 
374 static int cros_ec_chardev_probe(struct platform_device *pdev)
375 {
376 	struct cros_ec_dev *ec_dev = dev_get_drvdata(pdev->dev.parent);
377 	struct cros_ec_platform *ec_platform = dev_get_platdata(ec_dev->dev);
378 	struct chardev_data *data;
379 
380 	/* Create a char device: we want to create it anew */
381 	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
382 	if (!data)
383 		return -ENOMEM;
384 
385 	data->ec_dev = ec_dev;
386 	data->misc.minor = MISC_DYNAMIC_MINOR;
387 	data->misc.fops = &chardev_fops;
388 	data->misc.name = ec_platform->ec_name;
389 	data->misc.parent = pdev->dev.parent;
390 
391 	dev_set_drvdata(&pdev->dev, data);
392 
393 	return misc_register(&data->misc);
394 }
395 
396 static int cros_ec_chardev_remove(struct platform_device *pdev)
397 {
398 	struct chardev_data *data = dev_get_drvdata(&pdev->dev);
399 
400 	misc_deregister(&data->misc);
401 
402 	return 0;
403 }
404 
405 static struct platform_driver cros_ec_chardev_driver = {
406 	.driver = {
407 		.name = DRV_NAME,
408 	},
409 	.probe = cros_ec_chardev_probe,
410 	.remove = cros_ec_chardev_remove,
411 };
412 
413 module_platform_driver(cros_ec_chardev_driver);
414 
415 MODULE_ALIAS("platform:" DRV_NAME);
416 MODULE_AUTHOR("Enric Balletbo i Serra <enric.balletbo@collabora.com>");
417 MODULE_DESCRIPTION("ChromeOS EC Miscellaneous Character Driver");
418 MODULE_LICENSE("GPL");
419