xref: /linux/drivers/platform/chrome/cros_ec_chardev.c (revision 7f71507851fc7764b36a3221839607d3a45c2025) 
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/mod_devicetable.h>
18 #include <linux/module.h>
19 #include <linux/notifier.h>
20 #include <linux/platform_data/cros_ec_chardev.h>
21 #include <linux/platform_data/cros_ec_commands.h>
22 #include <linux/platform_data/cros_ec_proto.h>
23 #include <linux/platform_device.h>
24 #include <linux/poll.h>
25 #include <linux/slab.h>
26 #include <linux/types.h>
27 #include <linux/uaccess.h>
28 
29 #define DRV_NAME		"cros-ec-chardev"
30 
31 /* Arbitrary bounded size for the event queue */
32 #define CROS_MAX_EVENT_LEN	PAGE_SIZE
33 
34 struct chardev_data {
35 	struct cros_ec_dev *ec_dev;
36 	struct miscdevice misc;
37 };
38 
39 struct chardev_priv {
40 	struct cros_ec_dev *ec_dev;
41 	struct notifier_block notifier;
42 	wait_queue_head_t wait_event;
43 	unsigned long event_mask;
44 	struct list_head events;
45 	size_t event_len;
46 };
47 
48 struct ec_event {
49 	struct list_head node;
50 	size_t size;
51 	u8 event_type;
52 	u8 data[];
53 };
54 
55 static int ec_get_version(struct cros_ec_dev *ec, char *str, int maxlen)
56 {
57 	static const char * const current_image_name[] = {
58 		"unknown", "read-only", "read-write", "invalid",
59 	};
60 	struct ec_response_get_version *resp;
61 	struct cros_ec_command *msg;
62 	int ret;
63 
64 	msg = kzalloc(sizeof(*msg) + sizeof(*resp), GFP_KERNEL);
65 	if (!msg)
66 		return -ENOMEM;
67 
68 	msg->command = EC_CMD_GET_VERSION + ec->cmd_offset;
69 	msg->insize = sizeof(*resp);
70 
71 	ret = cros_ec_cmd_xfer_status(ec->ec_dev, msg);
72 	if (ret < 0) {
73 		snprintf(str, maxlen,
74 			 "Unknown EC version, returned error: %d\n",
75 			 msg->result);
76 		goto exit;
77 	}
78 
79 	resp = (struct ec_response_get_version *)msg->data;
80 	if (resp->current_image >= ARRAY_SIZE(current_image_name))
81 		resp->current_image = 3; /* invalid */
82 
83 	snprintf(str, maxlen, "%s\n%s\n%s\n%s\n", CROS_EC_DEV_VERSION,
84 		 resp->version_string_ro, resp->version_string_rw,
85 		 current_image_name[resp->current_image]);
86 
87 	ret = 0;
88 exit:
89 	kfree(msg);
90 	return ret;
91 }
92 
93 static int cros_ec_chardev_mkbp_event(struct notifier_block *nb,
94 				      unsigned long queued_during_suspend,
95 				      void *_notify)
96 {
97 	struct chardev_priv *priv = container_of(nb, struct chardev_priv,
98 						 notifier);
99 	struct cros_ec_device *ec_dev = priv->ec_dev->ec_dev;
100 	struct ec_event *event;
101 	unsigned long event_bit = 1 << ec_dev->event_data.event_type;
102 	int total_size = sizeof(*event) + ec_dev->event_size;
103 
104 	if (!(event_bit & priv->event_mask) ||
105 	    (priv->event_len + total_size) > CROS_MAX_EVENT_LEN)
106 		return NOTIFY_DONE;
107 
108 	event = kzalloc(total_size, GFP_KERNEL);
109 	if (!event)
110 		return NOTIFY_DONE;
111 
112 	event->size = ec_dev->event_size;
113 	event->event_type = ec_dev->event_data.event_type;
114 	memcpy(event->data, &ec_dev->event_data.data, ec_dev->event_size);
115 
116 	spin_lock(&priv->wait_event.lock);
117 	list_add_tail(&event->node, &priv->events);
118 	priv->event_len += total_size;
119 	wake_up_locked(&priv->wait_event);
120 	spin_unlock(&priv->wait_event.lock);
121 
122 	return NOTIFY_OK;
123 }
124 
125 static struct ec_event *cros_ec_chardev_fetch_event(struct chardev_priv *priv,
126 						    bool fetch, bool block)
127 {
128 	struct ec_event *event;
129 	int err;
130 
131 	spin_lock(&priv->wait_event.lock);
132 	if (!block && list_empty(&priv->events)) {
133 		event = ERR_PTR(-EWOULDBLOCK);
134 		goto out;
135 	}
136 
137 	if (!fetch) {
138 		event = NULL;
139 		goto out;
140 	}
141 
142 	err = wait_event_interruptible_locked(priv->wait_event,
143 					      !list_empty(&priv->events));
144 	if (err) {
145 		event = ERR_PTR(err);
146 		goto out;
147 	}
148 
149 	event = list_first_entry(&priv->events, struct ec_event, node);
150 	list_del(&event->node);
151 	priv->event_len -= sizeof(*event) + event->size;
152 
153 out:
154 	spin_unlock(&priv->wait_event.lock);
155 	return event;
156 }
157 
158 /*
159  * Device file ops
160  */
161 static int cros_ec_chardev_open(struct inode *inode, struct file *filp)
162 {
163 	struct miscdevice *mdev = filp->private_data;
164 	struct cros_ec_dev *ec_dev = dev_get_drvdata(mdev->parent);
165 	struct chardev_priv *priv;
166 	int ret;
167 
168 	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
169 	if (!priv)
170 		return -ENOMEM;
171 
172 	priv->ec_dev = ec_dev;
173 	filp->private_data = priv;
174 	INIT_LIST_HEAD(&priv->events);
175 	init_waitqueue_head(&priv->wait_event);
176 	nonseekable_open(inode, filp);
177 
178 	priv->notifier.notifier_call = cros_ec_chardev_mkbp_event;
179 	ret = blocking_notifier_chain_register(&ec_dev->ec_dev->event_notifier,
180 					       &priv->notifier);
181 	if (ret) {
182 		dev_err(ec_dev->dev, "failed to register event notifier\n");
183 		kfree(priv);
184 	}
185 
186 	return ret;
187 }
188 
189 static __poll_t cros_ec_chardev_poll(struct file *filp, poll_table *wait)
190 {
191 	struct chardev_priv *priv = filp->private_data;
192 
193 	poll_wait(filp, &priv->wait_event, wait);
194 
195 	if (list_empty(&priv->events))
196 		return 0;
197 
198 	return EPOLLIN | EPOLLRDNORM;
199 }
200 
201 static ssize_t cros_ec_chardev_read(struct file *filp, char __user *buffer,
202 				     size_t length, loff_t *offset)
203 {
204 	char msg[sizeof(struct ec_response_get_version) +
205 		 sizeof(CROS_EC_DEV_VERSION)];
206 	struct chardev_priv *priv = filp->private_data;
207 	struct cros_ec_dev *ec_dev = priv->ec_dev;
208 	size_t count;
209 	int ret;
210 
211 	if (priv->event_mask) { /* queued MKBP event */
212 		struct ec_event *event;
213 
214 		event = cros_ec_chardev_fetch_event(priv, length != 0,
215 						!(filp->f_flags & O_NONBLOCK));
216 		if (IS_ERR(event))
217 			return PTR_ERR(event);
218 		/*
219 		 * length == 0 is special - no IO is done but we check
220 		 * for error conditions.
221 		 */
222 		if (length == 0)
223 			return 0;
224 
225 		/* The event is 1 byte of type plus the payload */
226 		count = min(length, event->size + 1);
227 		ret = copy_to_user(buffer, &event->event_type, count);
228 		kfree(event);
229 		if (ret) /* the copy failed */
230 			return -EFAULT;
231 		*offset = count;
232 		return count;
233 	}
234 
235 	/*
236 	 * Legacy behavior if no event mask is defined
237 	 */
238 	if (*offset != 0)
239 		return 0;
240 
241 	ret = ec_get_version(ec_dev, msg, sizeof(msg));
242 	if (ret)
243 		return ret;
244 
245 	count = min(length, strlen(msg));
246 
247 	if (copy_to_user(buffer, msg, count))
248 		return -EFAULT;
249 
250 	*offset = count;
251 	return count;
252 }
253 
254 static int cros_ec_chardev_release(struct inode *inode, struct file *filp)
255 {
256 	struct chardev_priv *priv = filp->private_data;
257 	struct cros_ec_dev *ec_dev = priv->ec_dev;
258 	struct ec_event *event, *e;
259 
260 	blocking_notifier_chain_unregister(&ec_dev->ec_dev->event_notifier,
261 					   &priv->notifier);
262 
263 	list_for_each_entry_safe(event, e, &priv->events, node) {
264 		list_del(&event->node);
265 		kfree(event);
266 	}
267 	kfree(priv);
268 
269 	return 0;
270 }
271 
272 /*
273  * Ioctls
274  */
275 static long cros_ec_chardev_ioctl_xcmd(struct cros_ec_dev *ec, void __user *arg)
276 {
277 	struct cros_ec_command *s_cmd;
278 	struct cros_ec_command u_cmd;
279 	long ret;
280 
281 	if (copy_from_user(&u_cmd, arg, sizeof(u_cmd)))
282 		return -EFAULT;
283 
284 	if (u_cmd.outsize > EC_MAX_MSG_BYTES ||
285 	    u_cmd.insize > EC_MAX_MSG_BYTES)
286 		return -EINVAL;
287 
288 	s_cmd = kzalloc(sizeof(*s_cmd) + max(u_cmd.outsize, u_cmd.insize),
289 			GFP_KERNEL);
290 	if (!s_cmd)
291 		return -ENOMEM;
292 
293 	if (copy_from_user(s_cmd, arg, sizeof(*s_cmd) + u_cmd.outsize)) {
294 		ret = -EFAULT;
295 		goto exit;
296 	}
297 
298 	if (u_cmd.outsize != s_cmd->outsize ||
299 	    u_cmd.insize != s_cmd->insize) {
300 		ret = -EINVAL;
301 		goto exit;
302 	}
303 
304 	s_cmd->command += ec->cmd_offset;
305 	ret = cros_ec_cmd_xfer(ec->ec_dev, s_cmd);
306 	/* Only copy data to userland if data was received. */
307 	if (ret < 0)
308 		goto exit;
309 
310 	if (copy_to_user(arg, s_cmd, sizeof(*s_cmd) + s_cmd->insize))
311 		ret = -EFAULT;
312 exit:
313 	kfree(s_cmd);
314 	return ret;
315 }
316 
317 static long cros_ec_chardev_ioctl_readmem(struct cros_ec_dev *ec,
318 					   void __user *arg)
319 {
320 	struct cros_ec_device *ec_dev = ec->ec_dev;
321 	struct cros_ec_readmem s_mem = { };
322 	long num;
323 
324 	/* Not every platform supports direct reads */
325 	if (!ec_dev->cmd_readmem)
326 		return -ENOTTY;
327 
328 	if (copy_from_user(&s_mem, arg, sizeof(s_mem)))
329 		return -EFAULT;
330 
331 	if (s_mem.bytes > sizeof(s_mem.buffer))
332 		return -EINVAL;
333 
334 	num = ec_dev->cmd_readmem(ec_dev, s_mem.offset, s_mem.bytes,
335 				  s_mem.buffer);
336 	if (num <= 0)
337 		return num;
338 
339 	if (copy_to_user((void __user *)arg, &s_mem, sizeof(s_mem)))
340 		return -EFAULT;
341 
342 	return num;
343 }
344 
345 static long cros_ec_chardev_ioctl(struct file *filp, unsigned int cmd,
346 				   unsigned long arg)
347 {
348 	struct chardev_priv *priv = filp->private_data;
349 	struct cros_ec_dev *ec = priv->ec_dev;
350 
351 	if (_IOC_TYPE(cmd) != CROS_EC_DEV_IOC)
352 		return -ENOTTY;
353 
354 	switch (cmd) {
355 	case CROS_EC_DEV_IOCXCMD:
356 		return cros_ec_chardev_ioctl_xcmd(ec, (void __user *)arg);
357 	case CROS_EC_DEV_IOCRDMEM:
358 		return cros_ec_chardev_ioctl_readmem(ec, (void __user *)arg);
359 	case CROS_EC_DEV_IOCEVENTMASK:
360 		priv->event_mask = arg;
361 		return 0;
362 	}
363 
364 	return -ENOTTY;
365 }
366 
367 static const struct file_operations chardev_fops = {
368 	.open		= cros_ec_chardev_open,
369 	.poll		= cros_ec_chardev_poll,
370 	.read		= cros_ec_chardev_read,
371 	.release	= cros_ec_chardev_release,
372 	.unlocked_ioctl	= cros_ec_chardev_ioctl,
373 #ifdef CONFIG_COMPAT
374 	.compat_ioctl	= cros_ec_chardev_ioctl,
375 #endif
376 };
377 
378 static int cros_ec_chardev_probe(struct platform_device *pdev)
379 {
380 	struct cros_ec_dev *ec_dev = dev_get_drvdata(pdev->dev.parent);
381 	struct cros_ec_platform *ec_platform = dev_get_platdata(ec_dev->dev);
382 	struct chardev_data *data;
383 
384 	/* Create a char device: we want to create it anew */
385 	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
386 	if (!data)
387 		return -ENOMEM;
388 
389 	data->ec_dev = ec_dev;
390 	data->misc.minor = MISC_DYNAMIC_MINOR;
391 	data->misc.fops = &chardev_fops;
392 	data->misc.name = ec_platform->ec_name;
393 	data->misc.parent = pdev->dev.parent;
394 
395 	dev_set_drvdata(&pdev->dev, data);
396 
397 	return misc_register(&data->misc);
398 }
399 
400 static void cros_ec_chardev_remove(struct platform_device *pdev)
401 {
402 	struct chardev_data *data = dev_get_drvdata(&pdev->dev);
403 
404 	misc_deregister(&data->misc);
405 }
406 
407 static const struct platform_device_id cros_ec_chardev_id[] = {
408 	{ DRV_NAME, 0 },
409 	{}
410 };
411 MODULE_DEVICE_TABLE(platform, cros_ec_chardev_id);
412 
413 static struct platform_driver cros_ec_chardev_driver = {
414 	.driver = {
415 		.name = DRV_NAME,
416 	},
417 	.probe = cros_ec_chardev_probe,
418 	.remove = cros_ec_chardev_remove,
419 	.id_table = cros_ec_chardev_id,
420 };
421 
422 module_platform_driver(cros_ec_chardev_driver);
423 
424 MODULE_AUTHOR("Enric Balletbo i Serra <enric.balletbo@collabora.com>");
425 MODULE_DESCRIPTION("ChromeOS EC Miscellaneous Character Driver");
426 MODULE_LICENSE("GPL");
427