xref: /linux/drivers/platform/chrome/cros_ec_chardev.c (revision 07fdad3a93756b872da7b53647715c48d0f4a2d0) 
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_priv {
35 	struct cros_ec_device *ec_dev;
36 	struct notifier_block notifier;
37 	wait_queue_head_t wait_event;
38 	unsigned long event_mask;
39 	struct list_head events;
40 	size_t event_len;
41 	u16 cmd_offset;
42 };
43 
44 struct ec_event {
45 	struct list_head node;
46 	size_t size;
47 	u8 event_type;
48 	u8 data[];
49 };
50 
51 static int ec_get_version(struct chardev_priv *priv, char *str, int maxlen)
52 {
53 	static const char * const current_image_name[] = {
54 		"unknown", "read-only", "read-write", "invalid",
55 	};
56 	struct ec_response_get_version *resp;
57 	struct cros_ec_command *msg;
58 	int ret;
59 
60 	msg = kzalloc(sizeof(*msg) + sizeof(*resp), GFP_KERNEL);
61 	if (!msg)
62 		return -ENOMEM;
63 
64 	msg->command = EC_CMD_GET_VERSION + priv->cmd_offset;
65 	msg->insize = sizeof(*resp);
66 
67 	ret = cros_ec_cmd_xfer_status(priv->ec_dev, msg);
68 	if (ret < 0) {
69 		snprintf(str, maxlen,
70 			 "Unknown EC version, returned error: %d\n",
71 			 msg->result);
72 		goto exit;
73 	}
74 
75 	resp = (struct ec_response_get_version *)msg->data;
76 	if (resp->current_image >= ARRAY_SIZE(current_image_name))
77 		resp->current_image = 3; /* invalid */
78 
79 	snprintf(str, maxlen, "%s\n%s\n%s\n%s\n", CROS_EC_DEV_VERSION,
80 		 resp->version_string_ro, resp->version_string_rw,
81 		 current_image_name[resp->current_image]);
82 
83 	ret = 0;
84 exit:
85 	kfree(msg);
86 	return ret;
87 }
88 
89 static int cros_ec_chardev_mkbp_event(struct notifier_block *nb,
90 				      unsigned long queued_during_suspend,
91 				      void *_notify)
92 {
93 	struct chardev_priv *priv = container_of(nb, struct chardev_priv,
94 						 notifier);
95 	struct cros_ec_device *ec_dev = priv->ec_dev;
96 	struct ec_event *event;
97 	unsigned long event_bit = 1 << ec_dev->event_data.event_type;
98 	int total_size = sizeof(*event) + ec_dev->event_size;
99 
100 	if (!(event_bit & priv->event_mask) ||
101 	    (priv->event_len + total_size) > CROS_MAX_EVENT_LEN)
102 		return NOTIFY_DONE;
103 
104 	event = kzalloc(total_size, GFP_KERNEL);
105 	if (!event)
106 		return NOTIFY_DONE;
107 
108 	event->size = ec_dev->event_size;
109 	event->event_type = ec_dev->event_data.event_type;
110 	memcpy(event->data, &ec_dev->event_data.data, ec_dev->event_size);
111 
112 	spin_lock(&priv->wait_event.lock);
113 	list_add_tail(&event->node, &priv->events);
114 	priv->event_len += total_size;
115 	wake_up_locked(&priv->wait_event);
116 	spin_unlock(&priv->wait_event.lock);
117 
118 	return NOTIFY_OK;
119 }
120 
121 static struct ec_event *cros_ec_chardev_fetch_event(struct chardev_priv *priv,
122 						    bool fetch, bool block)
123 {
124 	struct ec_event *event;
125 	int err;
126 
127 	spin_lock(&priv->wait_event.lock);
128 	if (!block && list_empty(&priv->events)) {
129 		event = ERR_PTR(-EWOULDBLOCK);
130 		goto out;
131 	}
132 
133 	if (!fetch) {
134 		event = NULL;
135 		goto out;
136 	}
137 
138 	err = wait_event_interruptible_locked(priv->wait_event,
139 					      !list_empty(&priv->events));
140 	if (err) {
141 		event = ERR_PTR(err);
142 		goto out;
143 	}
144 
145 	event = list_first_entry(&priv->events, struct ec_event, node);
146 	list_del(&event->node);
147 	priv->event_len -= sizeof(*event) + event->size;
148 
149 out:
150 	spin_unlock(&priv->wait_event.lock);
151 	return event;
152 }
153 
154 /*
155  * Device file ops
156  */
157 static int cros_ec_chardev_open(struct inode *inode, struct file *filp)
158 {
159 	struct miscdevice *mdev = filp->private_data;
160 	struct cros_ec_dev *ec = dev_get_drvdata(mdev->parent);
161 	struct cros_ec_device *ec_dev = ec->ec_dev;
162 	struct chardev_priv *priv;
163 	int ret;
164 
165 	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
166 	if (!priv)
167 		return -ENOMEM;
168 
169 	priv->ec_dev = ec_dev;
170 	priv->cmd_offset = ec->cmd_offset;
171 	filp->private_data = priv;
172 	INIT_LIST_HEAD(&priv->events);
173 	init_waitqueue_head(&priv->wait_event);
174 	nonseekable_open(inode, filp);
175 
176 	priv->notifier.notifier_call = cros_ec_chardev_mkbp_event;
177 	ret = blocking_notifier_chain_register(&ec_dev->event_notifier,
178 					       &priv->notifier);
179 	if (ret) {
180 		dev_err(ec_dev->dev, "failed to register event notifier\n");
181 		kfree(priv);
182 	}
183 
184 	return ret;
185 }
186 
187 static __poll_t cros_ec_chardev_poll(struct file *filp, poll_table *wait)
188 {
189 	struct chardev_priv *priv = filp->private_data;
190 
191 	poll_wait(filp, &priv->wait_event, wait);
192 
193 	if (list_empty(&priv->events))
194 		return 0;
195 
196 	return EPOLLIN | EPOLLRDNORM;
197 }
198 
199 static ssize_t cros_ec_chardev_read(struct file *filp, char __user *buffer,
200 				     size_t length, loff_t *offset)
201 {
202 	char msg[sizeof(struct ec_response_get_version) +
203 		 sizeof(CROS_EC_DEV_VERSION)];
204 	struct chardev_priv *priv = filp->private_data;
205 	size_t count;
206 	int ret;
207 
208 	if (priv->event_mask) { /* queued MKBP event */
209 		struct ec_event *event;
210 
211 		event = cros_ec_chardev_fetch_event(priv, length != 0,
212 						!(filp->f_flags & O_NONBLOCK));
213 		if (IS_ERR(event))
214 			return PTR_ERR(event);
215 		/*
216 		 * length == 0 is special - no IO is done but we check
217 		 * for error conditions.
218 		 */
219 		if (length == 0)
220 			return 0;
221 
222 		/* The event is 1 byte of type plus the payload */
223 		count = min(length, event->size + 1);
224 		ret = copy_to_user(buffer, &event->event_type, count);
225 		kfree(event);
226 		if (ret) /* the copy failed */
227 			return -EFAULT;
228 		*offset = count;
229 		return count;
230 	}
231 
232 	/*
233 	 * Legacy behavior if no event mask is defined
234 	 */
235 	if (*offset != 0)
236 		return 0;
237 
238 	ret = ec_get_version(priv, msg, sizeof(msg));
239 	if (ret)
240 		return ret;
241 
242 	count = min(length, strlen(msg));
243 
244 	if (copy_to_user(buffer, msg, count))
245 		return -EFAULT;
246 
247 	*offset = count;
248 	return count;
249 }
250 
251 static int cros_ec_chardev_release(struct inode *inode, struct file *filp)
252 {
253 	struct chardev_priv *priv = filp->private_data;
254 	struct cros_ec_device *ec_dev = priv->ec_dev;
255 	struct ec_event *event, *e;
256 
257 	blocking_notifier_chain_unregister(&ec_dev->event_notifier,
258 					   &priv->notifier);
259 
260 	list_for_each_entry_safe(event, e, &priv->events, node) {
261 		list_del(&event->node);
262 		kfree(event);
263 	}
264 	kfree(priv);
265 
266 	return 0;
267 }
268 
269 /*
270  * Ioctls
271  */
272 static long cros_ec_chardev_ioctl_xcmd(struct chardev_priv *priv, void __user *arg)
273 {
274 	struct cros_ec_command *s_cmd;
275 	struct cros_ec_command u_cmd;
276 	long ret;
277 
278 	if (copy_from_user(&u_cmd, arg, sizeof(u_cmd)))
279 		return -EFAULT;
280 
281 	if (u_cmd.outsize > EC_MAX_MSG_BYTES ||
282 	    u_cmd.insize > EC_MAX_MSG_BYTES)
283 		return -EINVAL;
284 
285 	s_cmd = kzalloc(sizeof(*s_cmd) + max(u_cmd.outsize, u_cmd.insize),
286 			GFP_KERNEL);
287 	if (!s_cmd)
288 		return -ENOMEM;
289 
290 	if (copy_from_user(s_cmd, arg, sizeof(*s_cmd) + u_cmd.outsize)) {
291 		ret = -EFAULT;
292 		goto exit;
293 	}
294 
295 	if (u_cmd.outsize != s_cmd->outsize ||
296 	    u_cmd.insize != s_cmd->insize) {
297 		ret = -EINVAL;
298 		goto exit;
299 	}
300 
301 	s_cmd->command += priv->cmd_offset;
302 	ret = cros_ec_cmd_xfer(priv->ec_dev, s_cmd);
303 	/* Only copy data to userland if data was received. */
304 	if (ret < 0)
305 		goto exit;
306 
307 	if (copy_to_user(arg, s_cmd, sizeof(*s_cmd) + s_cmd->insize))
308 		ret = -EFAULT;
309 exit:
310 	kfree(s_cmd);
311 	return ret;
312 }
313 
314 static long cros_ec_chardev_ioctl_readmem(struct chardev_priv *priv, void __user *arg)
315 {
316 	struct cros_ec_device *ec_dev = priv->ec_dev;
317 	struct cros_ec_readmem s_mem = { };
318 	long num;
319 
320 	/* Not every platform supports direct reads */
321 	if (!ec_dev->cmd_readmem)
322 		return -ENOTTY;
323 
324 	if (copy_from_user(&s_mem, arg, sizeof(s_mem)))
325 		return -EFAULT;
326 
327 	if (s_mem.bytes > sizeof(s_mem.buffer))
328 		return -EINVAL;
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 
346 	if (_IOC_TYPE(cmd) != CROS_EC_DEV_IOC)
347 		return -ENOTTY;
348 
349 	switch (cmd) {
350 	case CROS_EC_DEV_IOCXCMD:
351 		return cros_ec_chardev_ioctl_xcmd(priv, (void __user *)arg);
352 	case CROS_EC_DEV_IOCRDMEM:
353 		return cros_ec_chardev_ioctl_readmem(priv, (void __user *)arg);
354 	case CROS_EC_DEV_IOCEVENTMASK:
355 		priv->event_mask = arg;
356 		return 0;
357 	}
358 
359 	return -ENOTTY;
360 }
361 
362 static const struct file_operations chardev_fops = {
363 	.open		= cros_ec_chardev_open,
364 	.poll		= cros_ec_chardev_poll,
365 	.read		= cros_ec_chardev_read,
366 	.release	= cros_ec_chardev_release,
367 	.unlocked_ioctl	= cros_ec_chardev_ioctl,
368 #ifdef CONFIG_COMPAT
369 	.compat_ioctl	= cros_ec_chardev_ioctl,
370 #endif
371 };
372 
373 static int cros_ec_chardev_probe(struct platform_device *pdev)
374 {
375 	struct cros_ec_dev *ec = dev_get_drvdata(pdev->dev.parent);
376 	struct cros_ec_platform *ec_platform = dev_get_platdata(ec->dev);
377 	struct miscdevice *misc;
378 
379 	/* Create a char device: we want to create it anew */
380 	misc = devm_kzalloc(&pdev->dev, sizeof(*misc), GFP_KERNEL);
381 	if (!misc)
382 		return -ENOMEM;
383 
384 	misc->minor = MISC_DYNAMIC_MINOR;
385 	misc->fops = &chardev_fops;
386 	misc->name = ec_platform->ec_name;
387 	misc->parent = pdev->dev.parent;
388 
389 	dev_set_drvdata(&pdev->dev, misc);
390 
391 	return misc_register(misc);
392 }
393 
394 static void cros_ec_chardev_remove(struct platform_device *pdev)
395 {
396 	struct miscdevice *misc = dev_get_drvdata(&pdev->dev);
397 
398 	misc_deregister(misc);
399 }
400 
401 static const struct platform_device_id cros_ec_chardev_id[] = {
402 	{ DRV_NAME, 0 },
403 	{}
404 };
405 MODULE_DEVICE_TABLE(platform, cros_ec_chardev_id);
406 
407 static struct platform_driver cros_ec_chardev_driver = {
408 	.driver = {
409 		.name = DRV_NAME,
410 	},
411 	.probe = cros_ec_chardev_probe,
412 	.remove = cros_ec_chardev_remove,
413 	.id_table = cros_ec_chardev_id,
414 };
415 
416 module_platform_driver(cros_ec_chardev_driver);
417 
418 MODULE_AUTHOR("Enric Balletbo i Serra <enric.balletbo@collabora.com>");
419 MODULE_DESCRIPTION("ChromeOS EC Miscellaneous Character Driver");
420 MODULE_LICENSE("GPL");
421