1// SPDX-License-Identifier: GPL-2.0
2
3/*
4 * IPMB driver to receive a request and send a response
5 *
6 * Copyright (C) 2019 Mellanox Techologies, Ltd.
7 *
8 * This was inspired by Brendan Higgins' ipmi-bmc-bt-i2c driver.
9 */
10
11#include <linux/acpi.h>
12#include <linux/errno.h>
13#include <linux/i2c.h>
14#include <linux/miscdevice.h>
15#include <linux/module.h>
16#include <linux/mutex.h>
17#include <linux/poll.h>
18#include <linux/slab.h>
19#include <linux/spinlock.h>
20#include <linux/wait.h>
21
22#define MAX_MSG_LEN		240
23#define IPMB_REQUEST_LEN_MIN	7
24#define NETFN_RSP_BIT_MASK	0x4
25#define REQUEST_QUEUE_MAX_LEN	256
26
27#define IPMB_MSG_LEN_IDX	0
28#define RQ_SA_8BIT_IDX		1
29#define NETFN_LUN_IDX		2
30
31#define GET_7BIT_ADDR(addr_8bit)	(addr_8bit >> 1)
32#define GET_8BIT_ADDR(addr_7bit)	((addr_7bit << 1) & 0xff)
33
34#define IPMB_MSG_PAYLOAD_LEN_MAX (MAX_MSG_LEN - IPMB_REQUEST_LEN_MIN - 1)
35
36#define SMBUS_MSG_HEADER_LENGTH	2
37#define SMBUS_MSG_IDX_OFFSET	(SMBUS_MSG_HEADER_LENGTH + 1)
38
39struct ipmb_msg {
40	u8 len;
41	u8 rs_sa;
42	u8 netfn_rs_lun;
43	u8 checksum1;
44	u8 rq_sa;
45	u8 rq_seq_rq_lun;
46	u8 cmd;
47	u8 payload[IPMB_MSG_PAYLOAD_LEN_MAX];
48	/* checksum2 is included in payload */
49} __packed;
50
51struct ipmb_request_elem {
52	struct list_head list;
53	struct ipmb_msg request;
54};
55
56struct ipmb_dev {
57	struct i2c_client *client;
58	struct miscdevice miscdev;
59	struct ipmb_msg request;
60	struct list_head request_queue;
61	atomic_t request_queue_len;
62	size_t msg_idx;
63	spinlock_t lock;
64	wait_queue_head_t wait_queue;
65	struct mutex file_mutex;
66	bool is_i2c_protocol;
67};
68
69static inline struct ipmb_dev *to_ipmb_dev(struct file *file)
70{
71	return container_of(file->private_data, struct ipmb_dev, miscdev);
72}
73
74static ssize_t ipmb_read(struct file *file, char __user *buf, size_t count,
75			loff_t *ppos)
76{
77	struct ipmb_dev *ipmb_dev = to_ipmb_dev(file);
78	struct ipmb_request_elem *queue_elem;
79	struct ipmb_msg msg;
80	ssize_t ret = 0;
81
82	memset(&msg, 0, sizeof(msg));
83
84	spin_lock_irq(&ipmb_dev->lock);
85
86	while (list_empty(&ipmb_dev->request_queue)) {
87		spin_unlock_irq(&ipmb_dev->lock);
88
89		if (file->f_flags & O_NONBLOCK)
90			return -EAGAIN;
91
92		ret = wait_event_interruptible(ipmb_dev->wait_queue,
93				!list_empty(&ipmb_dev->request_queue));
94		if (ret)
95			return ret;
96
97		spin_lock_irq(&ipmb_dev->lock);
98	}
99
100	queue_elem = list_first_entry(&ipmb_dev->request_queue,
101					struct ipmb_request_elem, list);
102	memcpy(&msg, &queue_elem->request, sizeof(msg));
103	list_del(&queue_elem->list);
104	kfree(queue_elem);
105	atomic_dec(&ipmb_dev->request_queue_len);
106
107	spin_unlock_irq(&ipmb_dev->lock);
108
109	count = min_t(size_t, count, msg.len + 1);
110	if (copy_to_user(buf, &msg, count))
111		ret = -EFAULT;
112
113	return ret < 0 ? ret : count;
114}
115
116static int ipmb_i2c_write(struct i2c_client *client, u8 *msg, u8 addr)
117{
118	struct i2c_msg i2c_msg;
119
120	/*
121	 * subtract 1 byte (rq_sa) from the length of the msg passed to
122	 * raw i2c_transfer
123	 */
124	i2c_msg.len = msg[IPMB_MSG_LEN_IDX] - 1;
125
126	/* Assign message to buffer except first 2 bytes (length and address) */
127	i2c_msg.buf = msg + 2;
128
129	i2c_msg.addr = addr;
130	i2c_msg.flags = client->flags & I2C_CLIENT_PEC;
131
132	return i2c_transfer(client->adapter, &i2c_msg, 1);
133}
134
135static ssize_t ipmb_write(struct file *file, const char __user *buf,
136			size_t count, loff_t *ppos)
137{
138	struct ipmb_dev *ipmb_dev = to_ipmb_dev(file);
139	u8 rq_sa, netf_rq_lun, msg_len;
140	struct i2c_client *temp_client;
141	u8 msg[MAX_MSG_LEN];
142	ssize_t ret;
143
144	if (count > sizeof(msg))
145		return -EINVAL;
146
147	if (copy_from_user(&msg, buf, count))
148		return -EFAULT;
149
150	if (count < msg[0])
151		return -EINVAL;
152
153	rq_sa = GET_7BIT_ADDR(msg[RQ_SA_8BIT_IDX]);
154	netf_rq_lun = msg[NETFN_LUN_IDX];
155
156	/* Check i2c block transfer vs smbus */
157	if (ipmb_dev->is_i2c_protocol) {
158		ret = ipmb_i2c_write(ipmb_dev->client, msg, rq_sa);
159		return (ret == 1) ? count : ret;
160	}
161
162	/*
163	 * subtract rq_sa and netf_rq_lun from the length of the msg. Fill the
164	 * temporary client. Note that its use is an exception for IPMI.
165	 */
166	msg_len = msg[IPMB_MSG_LEN_IDX] - SMBUS_MSG_HEADER_LENGTH;
167	temp_client = kmemdup(ipmb_dev->client, sizeof(*temp_client), GFP_KERNEL);
168	if (!temp_client)
169		return -ENOMEM;
170
171	temp_client->addr = rq_sa;
172
173	ret = i2c_smbus_write_block_data(temp_client, netf_rq_lun, msg_len,
174					 msg + SMBUS_MSG_IDX_OFFSET);
175	kfree(temp_client);
176
177	return ret < 0 ? ret : count;
178}
179
180static __poll_t ipmb_poll(struct file *file, poll_table *wait)
181{
182	struct ipmb_dev *ipmb_dev = to_ipmb_dev(file);
183	__poll_t mask = EPOLLOUT;
184
185	mutex_lock(&ipmb_dev->file_mutex);
186	poll_wait(file, &ipmb_dev->wait_queue, wait);
187
188	if (atomic_read(&ipmb_dev->request_queue_len))
189		mask |= EPOLLIN;
190	mutex_unlock(&ipmb_dev->file_mutex);
191
192	return mask;
193}
194
195static const struct file_operations ipmb_fops = {
196	.owner	= THIS_MODULE,
197	.read	= ipmb_read,
198	.write	= ipmb_write,
199	.poll	= ipmb_poll,
200};
201
202/* Called with ipmb_dev->lock held. */
203static void ipmb_handle_request(struct ipmb_dev *ipmb_dev)
204{
205	struct ipmb_request_elem *queue_elem;
206
207	if (atomic_read(&ipmb_dev->request_queue_len) >=
208			REQUEST_QUEUE_MAX_LEN)
209		return;
210
211	queue_elem = kmalloc(sizeof(*queue_elem), GFP_ATOMIC);
212	if (!queue_elem)
213		return;
214
215	memcpy(&queue_elem->request, &ipmb_dev->request,
216		sizeof(struct ipmb_msg));
217	list_add(&queue_elem->list, &ipmb_dev->request_queue);
218	atomic_inc(&ipmb_dev->request_queue_len);
219	wake_up_all(&ipmb_dev->wait_queue);
220}
221
222static u8 ipmb_verify_checksum1(struct ipmb_dev *ipmb_dev, u8 rs_sa)
223{
224	/* The 8 lsb of the sum is 0 when the checksum is valid */
225	return (rs_sa + ipmb_dev->request.netfn_rs_lun +
226		ipmb_dev->request.checksum1);
227}
228
229/*
230 * Verify if message has proper ipmb header with minimum length
231 * and correct checksum byte.
232 */
233static bool is_ipmb_msg(struct ipmb_dev *ipmb_dev, u8 rs_sa)
234{
235	if ((ipmb_dev->msg_idx >= IPMB_REQUEST_LEN_MIN) &&
236	   (!ipmb_verify_checksum1(ipmb_dev, rs_sa)))
237		return true;
238
239	return false;
240}
241
242/*
243 * The IPMB protocol only supports I2C Writes so there is no need
244 * to support I2C_SLAVE_READ* events.
245 * This i2c callback function only monitors IPMB request messages
246 * and adds them in a queue, so that they can be handled by
247 * receive_ipmb_request.
248 */
249static int ipmb_slave_cb(struct i2c_client *client,
250			enum i2c_slave_event event, u8 *val)
251{
252	struct ipmb_dev *ipmb_dev = i2c_get_clientdata(client);
253	u8 *buf = (u8 *)&ipmb_dev->request;
254	unsigned long flags;
255
256	spin_lock_irqsave(&ipmb_dev->lock, flags);
257	switch (event) {
258	case I2C_SLAVE_WRITE_REQUESTED:
259		memset(&ipmb_dev->request, 0, sizeof(ipmb_dev->request));
260		ipmb_dev->msg_idx = 0;
261
262		/*
263		 * At index 0, ipmb_msg stores the length of msg,
264		 * skip it for now.
265		 * The len will be populated once the whole
266		 * buf is populated.
267		 *
268		 * The I2C bus driver's responsibility is to pass the
269		 * data bytes to the backend driver; it does not
270		 * forward the i2c slave address.
271		 * Since the first byte in the IPMB message is the
272		 * address of the responder, it is the responsibility
273		 * of the IPMB driver to format the message properly.
274		 * So this driver prepends the address of the responder
275		 * to the received i2c data before the request message
276		 * is handled in userland.
277		 */
278		buf[++ipmb_dev->msg_idx] = GET_8BIT_ADDR(client->addr);
279		break;
280
281	case I2C_SLAVE_WRITE_RECEIVED:
282		if (ipmb_dev->msg_idx >= sizeof(struct ipmb_msg) - 1)
283			break;
284
285		buf[++ipmb_dev->msg_idx] = *val;
286		break;
287
288	case I2C_SLAVE_STOP:
289		ipmb_dev->request.len = ipmb_dev->msg_idx;
290		if (is_ipmb_msg(ipmb_dev, GET_8BIT_ADDR(client->addr)))
291			ipmb_handle_request(ipmb_dev);
292		break;
293
294	default:
295		break;
296	}
297	spin_unlock_irqrestore(&ipmb_dev->lock, flags);
298
299	return 0;
300}
301
302static int ipmb_probe(struct i2c_client *client)
303{
304	struct ipmb_dev *ipmb_dev;
305	int ret;
306
307	ipmb_dev = devm_kzalloc(&client->dev, sizeof(*ipmb_dev),
308					GFP_KERNEL);
309	if (!ipmb_dev)
310		return -ENOMEM;
311
312	spin_lock_init(&ipmb_dev->lock);
313	init_waitqueue_head(&ipmb_dev->wait_queue);
314	atomic_set(&ipmb_dev->request_queue_len, 0);
315	INIT_LIST_HEAD(&ipmb_dev->request_queue);
316
317	mutex_init(&ipmb_dev->file_mutex);
318
319	ipmb_dev->miscdev.minor = MISC_DYNAMIC_MINOR;
320
321	ipmb_dev->miscdev.name = devm_kasprintf(&client->dev, GFP_KERNEL,
322						"%s%d", "ipmb-",
323						client->adapter->nr);
324	ipmb_dev->miscdev.fops = &ipmb_fops;
325	ipmb_dev->miscdev.parent = &client->dev;
326	ret = misc_register(&ipmb_dev->miscdev);
327	if (ret)
328		return ret;
329
330	ipmb_dev->is_i2c_protocol
331		= device_property_read_bool(&client->dev, "i2c-protocol");
332
333	ipmb_dev->client = client;
334	i2c_set_clientdata(client, ipmb_dev);
335	ret = i2c_slave_register(client, ipmb_slave_cb);
336	if (ret) {
337		misc_deregister(&ipmb_dev->miscdev);
338		return ret;
339	}
340
341	return 0;
342}
343
344static void ipmb_remove(struct i2c_client *client)
345{
346	struct ipmb_dev *ipmb_dev = i2c_get_clientdata(client);
347
348	i2c_slave_unregister(client);
349	misc_deregister(&ipmb_dev->miscdev);
350}
351
352static const struct i2c_device_id ipmb_id[] = {
353	{ "ipmb-dev", 0 },
354	{},
355};
356MODULE_DEVICE_TABLE(i2c, ipmb_id);
357
358static const struct acpi_device_id acpi_ipmb_id[] = {
359	{ "IPMB0001", 0 },
360	{},
361};
362MODULE_DEVICE_TABLE(acpi, acpi_ipmb_id);
363
364static struct i2c_driver ipmb_driver = {
365	.driver = {
366		.name = "ipmb-dev",
367		.acpi_match_table = ACPI_PTR(acpi_ipmb_id),
368	},
369	.probe = ipmb_probe,
370	.remove = ipmb_remove,
371	.id_table = ipmb_id,
372};
373module_i2c_driver(ipmb_driver);
374
375MODULE_AUTHOR("Mellanox Technologies");
376MODULE_DESCRIPTION("IPMB driver");
377MODULE_LICENSE("GPL v2");
378