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
39 struct 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
51 struct ipmb_request_elem {
52 struct list_head list;
53 struct ipmb_msg request;
54 };
55
56 struct 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
to_ipmb_dev(struct file * file)69 static inline struct ipmb_dev *to_ipmb_dev(struct file *file)
70 {
71 return container_of(file->private_data, struct ipmb_dev, miscdev);
72 }
73
ipmb_read(struct file * file,char __user * buf,size_t count,loff_t * ppos)74 static 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
ipmb_i2c_write(struct i2c_client * client,u8 * msg,u8 addr)116 static 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
ipmb_write(struct file * file,const char __user * buf,size_t count,loff_t * ppos)135 static 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 union i2c_smbus_data data;
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 passed to
164 * i2c_smbus_xfer
165 */
166 msg_len = msg[IPMB_MSG_LEN_IDX] - SMBUS_MSG_HEADER_LENGTH;
167 if (msg_len > I2C_SMBUS_BLOCK_MAX)
168 msg_len = I2C_SMBUS_BLOCK_MAX;
169
170 data.block[0] = msg_len;
171 memcpy(&data.block[1], msg + SMBUS_MSG_IDX_OFFSET, msg_len);
172 ret = i2c_smbus_xfer(ipmb_dev->client->adapter, rq_sa,
173 ipmb_dev->client->flags,
174 I2C_SMBUS_WRITE, netf_rq_lun,
175 I2C_SMBUS_BLOCK_DATA, &data);
176
177 return ret ? : count;
178 }
179
ipmb_poll(struct file * file,poll_table * wait)180 static __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
195 static 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. */
ipmb_handle_request(struct ipmb_dev * ipmb_dev)203 static 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
ipmb_verify_checksum1(struct ipmb_dev * ipmb_dev,u8 rs_sa)222 static 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 */
is_ipmb_msg(struct ipmb_dev * ipmb_dev,u8 rs_sa)233 static 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 */
ipmb_slave_cb(struct i2c_client * client,enum i2c_slave_event event,u8 * val)249 static 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
ipmb_probe(struct i2c_client * client,const struct i2c_device_id * id)302 static int ipmb_probe(struct i2c_client *client,
303 const struct i2c_device_id *id)
304 {
305 struct ipmb_dev *ipmb_dev;
306 int ret;
307
308 ipmb_dev = devm_kzalloc(&client->dev, sizeof(*ipmb_dev),
309 GFP_KERNEL);
310 if (!ipmb_dev)
311 return -ENOMEM;
312
313 spin_lock_init(&ipmb_dev->lock);
314 init_waitqueue_head(&ipmb_dev->wait_queue);
315 atomic_set(&ipmb_dev->request_queue_len, 0);
316 INIT_LIST_HEAD(&ipmb_dev->request_queue);
317
318 mutex_init(&ipmb_dev->file_mutex);
319
320 ipmb_dev->miscdev.minor = MISC_DYNAMIC_MINOR;
321
322 ipmb_dev->miscdev.name = devm_kasprintf(&client->dev, GFP_KERNEL,
323 "%s%d", "ipmb-",
324 client->adapter->nr);
325 ipmb_dev->miscdev.fops = &ipmb_fops;
326 ipmb_dev->miscdev.parent = &client->dev;
327 ret = misc_register(&ipmb_dev->miscdev);
328 if (ret)
329 return ret;
330
331 ipmb_dev->is_i2c_protocol
332 = device_property_read_bool(&client->dev, "i2c-protocol");
333
334 ipmb_dev->client = client;
335 i2c_set_clientdata(client, ipmb_dev);
336 ret = i2c_slave_register(client, ipmb_slave_cb);
337 if (ret) {
338 misc_deregister(&ipmb_dev->miscdev);
339 return ret;
340 }
341
342 return 0;
343 }
344
ipmb_remove(struct i2c_client * client)345 static int ipmb_remove(struct i2c_client *client)
346 {
347 struct ipmb_dev *ipmb_dev = i2c_get_clientdata(client);
348
349 i2c_slave_unregister(client);
350 misc_deregister(&ipmb_dev->miscdev);
351
352 return 0;
353 }
354
355 static const struct i2c_device_id ipmb_id[] = {
356 { "ipmb-dev", 0 },
357 {},
358 };
359 MODULE_DEVICE_TABLE(i2c, ipmb_id);
360
361 static const struct acpi_device_id acpi_ipmb_id[] = {
362 { "IPMB0001", 0 },
363 {},
364 };
365 MODULE_DEVICE_TABLE(acpi, acpi_ipmb_id);
366
367 static struct i2c_driver ipmb_driver = {
368 .driver = {
369 .name = "ipmb-dev",
370 .acpi_match_table = ACPI_PTR(acpi_ipmb_id),
371 },
372 .probe = ipmb_probe,
373 .remove = ipmb_remove,
374 .id_table = ipmb_id,
375 };
376 module_i2c_driver(ipmb_driver);
377
378 MODULE_AUTHOR("Mellanox Technologies");
379 MODULE_DESCRIPTION("IPMB driver");
380 MODULE_LICENSE("GPL v2");
381
