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 128
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 };
67
to_ipmb_dev(struct file * file)68 static inline struct ipmb_dev *to_ipmb_dev(struct file *file)
69 {
70 return container_of(file->private_data, struct ipmb_dev, miscdev);
71 }
72
ipmb_read(struct file * file,char __user * buf,size_t count,loff_t * ppos)73 static ssize_t ipmb_read(struct file *file, char __user *buf, size_t count,
74 loff_t *ppos)
75 {
76 struct ipmb_dev *ipmb_dev = to_ipmb_dev(file);
77 struct ipmb_request_elem *queue_elem;
78 struct ipmb_msg msg;
79 ssize_t ret = 0;
80
81 memset(&msg, 0, sizeof(msg));
82
83 spin_lock_irq(&ipmb_dev->lock);
84
85 while (list_empty(&ipmb_dev->request_queue)) {
86 spin_unlock_irq(&ipmb_dev->lock);
87
88 if (file->f_flags & O_NONBLOCK)
89 return -EAGAIN;
90
91 ret = wait_event_interruptible(ipmb_dev->wait_queue,
92 !list_empty(&ipmb_dev->request_queue));
93 if (ret)
94 return ret;
95
96 spin_lock_irq(&ipmb_dev->lock);
97 }
98
99 queue_elem = list_first_entry(&ipmb_dev->request_queue,
100 struct ipmb_request_elem, list);
101 memcpy(&msg, &queue_elem->request, sizeof(msg));
102 list_del(&queue_elem->list);
103 kfree(queue_elem);
104 atomic_dec(&ipmb_dev->request_queue_len);
105
106 spin_unlock_irq(&ipmb_dev->lock);
107
108 count = min_t(size_t, count, msg.len + 1);
109 if (copy_to_user(buf, &msg, count))
110 ret = -EFAULT;
111
112 return ret < 0 ? ret : count;
113 }
114
ipmb_write(struct file * file,const char __user * buf,size_t count,loff_t * ppos)115 static ssize_t ipmb_write(struct file *file, const char __user *buf,
116 size_t count, loff_t *ppos)
117 {
118 struct ipmb_dev *ipmb_dev = to_ipmb_dev(file);
119 u8 rq_sa, netf_rq_lun, msg_len;
120 union i2c_smbus_data data;
121 u8 msg[MAX_MSG_LEN];
122 ssize_t ret;
123
124 if (count > sizeof(msg))
125 return -EINVAL;
126
127 if (copy_from_user(&msg, buf, count))
128 return -EFAULT;
129
130 if (count < msg[0])
131 return -EINVAL;
132
133 rq_sa = GET_7BIT_ADDR(msg[RQ_SA_8BIT_IDX]);
134 netf_rq_lun = msg[NETFN_LUN_IDX];
135
136 if (!(netf_rq_lun & NETFN_RSP_BIT_MASK))
137 return -EINVAL;
138
139 /*
140 * subtract rq_sa and netf_rq_lun from the length of the msg passed to
141 * i2c_smbus_xfer
142 */
143 msg_len = msg[IPMB_MSG_LEN_IDX] - SMBUS_MSG_HEADER_LENGTH;
144 if (msg_len > I2C_SMBUS_BLOCK_MAX)
145 msg_len = I2C_SMBUS_BLOCK_MAX;
146
147 data.block[0] = msg_len;
148 memcpy(&data.block[1], msg + SMBUS_MSG_IDX_OFFSET, msg_len);
149 ret = i2c_smbus_xfer(ipmb_dev->client->adapter, rq_sa,
150 ipmb_dev->client->flags,
151 I2C_SMBUS_WRITE, netf_rq_lun,
152 I2C_SMBUS_BLOCK_DATA, &data);
153
154 return ret ? : count;
155 }
156
ipmb_poll(struct file * file,poll_table * wait)157 static unsigned int ipmb_poll(struct file *file, poll_table *wait)
158 {
159 struct ipmb_dev *ipmb_dev = to_ipmb_dev(file);
160 unsigned int mask = POLLOUT;
161
162 mutex_lock(&ipmb_dev->file_mutex);
163 poll_wait(file, &ipmb_dev->wait_queue, wait);
164
165 if (atomic_read(&ipmb_dev->request_queue_len))
166 mask |= POLLIN;
167 mutex_unlock(&ipmb_dev->file_mutex);
168
169 return mask;
170 }
171
172 static const struct file_operations ipmb_fops = {
173 .owner = THIS_MODULE,
174 .read = ipmb_read,
175 .write = ipmb_write,
176 .poll = ipmb_poll,
177 };
178
179 /* Called with ipmb_dev->lock held. */
ipmb_handle_request(struct ipmb_dev * ipmb_dev)180 static void ipmb_handle_request(struct ipmb_dev *ipmb_dev)
181 {
182 struct ipmb_request_elem *queue_elem;
183
184 if (atomic_read(&ipmb_dev->request_queue_len) >=
185 REQUEST_QUEUE_MAX_LEN)
186 return;
187
188 queue_elem = kmalloc(sizeof(*queue_elem), GFP_ATOMIC);
189 if (!queue_elem)
190 return;
191
192 memcpy(&queue_elem->request, &ipmb_dev->request,
193 sizeof(struct ipmb_msg));
194 list_add(&queue_elem->list, &ipmb_dev->request_queue);
195 atomic_inc(&ipmb_dev->request_queue_len);
196 wake_up_all(&ipmb_dev->wait_queue);
197 }
198
ipmb_verify_checksum1(struct ipmb_dev * ipmb_dev,u8 rs_sa)199 static u8 ipmb_verify_checksum1(struct ipmb_dev *ipmb_dev, u8 rs_sa)
200 {
201 /* The 8 lsb of the sum is 0 when the checksum is valid */
202 return (rs_sa + ipmb_dev->request.netfn_rs_lun +
203 ipmb_dev->request.checksum1);
204 }
205
is_ipmb_request(struct ipmb_dev * ipmb_dev,u8 rs_sa)206 static bool is_ipmb_request(struct ipmb_dev *ipmb_dev, u8 rs_sa)
207 {
208 if (ipmb_dev->msg_idx >= IPMB_REQUEST_LEN_MIN) {
209 if (ipmb_verify_checksum1(ipmb_dev, rs_sa))
210 return false;
211
212 /*
213 * Check whether this is an IPMB request or
214 * response.
215 * The 6 MSB of netfn_rs_lun are dedicated to the netfn
216 * while the remaining bits are dedicated to the lun.
217 * If the LSB of the netfn is cleared, it is associated
218 * with an IPMB request.
219 * If the LSB of the netfn is set, it is associated with
220 * an IPMB response.
221 */
222 if (!(ipmb_dev->request.netfn_rs_lun & NETFN_RSP_BIT_MASK))
223 return true;
224 }
225 return false;
226 }
227
228 /*
229 * The IPMB protocol only supports I2C Writes so there is no need
230 * to support I2C_SLAVE_READ* events.
231 * This i2c callback function only monitors IPMB request messages
232 * and adds them in a queue, so that they can be handled by
233 * receive_ipmb_request.
234 */
ipmb_slave_cb(struct i2c_client * client,enum i2c_slave_event event,u8 * val)235 static int ipmb_slave_cb(struct i2c_client *client,
236 enum i2c_slave_event event, u8 *val)
237 {
238 struct ipmb_dev *ipmb_dev = i2c_get_clientdata(client);
239 u8 *buf = (u8 *)&ipmb_dev->request;
240 unsigned long flags;
241
242 spin_lock_irqsave(&ipmb_dev->lock, flags);
243 switch (event) {
244 case I2C_SLAVE_WRITE_REQUESTED:
245 memset(&ipmb_dev->request, 0, sizeof(ipmb_dev->request));
246 ipmb_dev->msg_idx = 0;
247
248 /*
249 * At index 0, ipmb_msg stores the length of msg,
250 * skip it for now.
251 * The len will be populated once the whole
252 * buf is populated.
253 *
254 * The I2C bus driver's responsibility is to pass the
255 * data bytes to the backend driver; it does not
256 * forward the i2c slave address.
257 * Since the first byte in the IPMB message is the
258 * address of the responder, it is the responsibility
259 * of the IPMB driver to format the message properly.
260 * So this driver prepends the address of the responder
261 * to the received i2c data before the request message
262 * is handled in userland.
263 */
264 buf[++ipmb_dev->msg_idx] = GET_8BIT_ADDR(client->addr);
265 break;
266
267 case I2C_SLAVE_WRITE_RECEIVED:
268 if (ipmb_dev->msg_idx >= sizeof(struct ipmb_msg))
269 break;
270
271 buf[++ipmb_dev->msg_idx] = *val;
272 break;
273
274 case I2C_SLAVE_STOP:
275 ipmb_dev->request.len = ipmb_dev->msg_idx;
276
277 if (is_ipmb_request(ipmb_dev, GET_8BIT_ADDR(client->addr)))
278 ipmb_handle_request(ipmb_dev);
279 break;
280
281 default:
282 break;
283 }
284 spin_unlock_irqrestore(&ipmb_dev->lock, flags);
285
286 return 0;
287 }
288
ipmb_probe(struct i2c_client * client,const struct i2c_device_id * id)289 static int ipmb_probe(struct i2c_client *client,
290 const struct i2c_device_id *id)
291 {
292 struct ipmb_dev *ipmb_dev;
293 int ret;
294
295 ipmb_dev = devm_kzalloc(&client->dev, sizeof(*ipmb_dev),
296 GFP_KERNEL);
297 if (!ipmb_dev)
298 return -ENOMEM;
299
300 spin_lock_init(&ipmb_dev->lock);
301 init_waitqueue_head(&ipmb_dev->wait_queue);
302 atomic_set(&ipmb_dev->request_queue_len, 0);
303 INIT_LIST_HEAD(&ipmb_dev->request_queue);
304
305 mutex_init(&ipmb_dev->file_mutex);
306
307 ipmb_dev->miscdev.minor = MISC_DYNAMIC_MINOR;
308
309 ipmb_dev->miscdev.name = devm_kasprintf(&client->dev, GFP_KERNEL,
310 "%s%d", "ipmb-",
311 client->adapter->nr);
312 ipmb_dev->miscdev.fops = &ipmb_fops;
313 ipmb_dev->miscdev.parent = &client->dev;
314 ret = misc_register(&ipmb_dev->miscdev);
315 if (ret)
316 return ret;
317
318 ipmb_dev->client = client;
319 i2c_set_clientdata(client, ipmb_dev);
320 ret = i2c_slave_register(client, ipmb_slave_cb);
321 if (ret) {
322 misc_deregister(&ipmb_dev->miscdev);
323 return ret;
324 }
325
326 return 0;
327 }
328
ipmb_remove(struct i2c_client * client)329 static int ipmb_remove(struct i2c_client *client)
330 {
331 struct ipmb_dev *ipmb_dev = i2c_get_clientdata(client);
332
333 i2c_slave_unregister(client);
334 misc_deregister(&ipmb_dev->miscdev);
335
336 return 0;
337 }
338
339 static const struct i2c_device_id ipmb_id[] = {
340 { "ipmb-dev", 0 },
341 {},
342 };
343 MODULE_DEVICE_TABLE(i2c, ipmb_id);
344
345 static const struct acpi_device_id acpi_ipmb_id[] = {
346 { "IPMB0001", 0 },
347 {},
348 };
349 MODULE_DEVICE_TABLE(acpi, acpi_ipmb_id);
350
351 static struct i2c_driver ipmb_driver = {
352 .driver = {
353 .name = "ipmb-dev",
354 .acpi_match_table = ACPI_PTR(acpi_ipmb_id),
355 },
356 .probe = ipmb_probe,
357 .remove = ipmb_remove,
358 .id_table = ipmb_id,
359 };
360 module_i2c_driver(ipmb_driver);
361
362 MODULE_AUTHOR("Mellanox Technologies");
363 MODULE_DESCRIPTION("IPMB driver");
364 MODULE_LICENSE("GPL v2");
365