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 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 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 } 114 115 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 /* 137 * subtract rq_sa and netf_rq_lun from the length of the msg passed to 138 * i2c_smbus_xfer 139 */ 140 msg_len = msg[IPMB_MSG_LEN_IDX] - SMBUS_MSG_HEADER_LENGTH; 141 if (msg_len > I2C_SMBUS_BLOCK_MAX) 142 msg_len = I2C_SMBUS_BLOCK_MAX; 143 144 data.block[0] = msg_len; 145 memcpy(&data.block[1], msg + SMBUS_MSG_IDX_OFFSET, msg_len); 146 ret = i2c_smbus_xfer(ipmb_dev->client->adapter, rq_sa, 147 ipmb_dev->client->flags, 148 I2C_SMBUS_WRITE, netf_rq_lun, 149 I2C_SMBUS_BLOCK_DATA, &data); 150 151 return ret ? : count; 152 } 153 154 static __poll_t ipmb_poll(struct file *file, poll_table *wait) 155 { 156 struct ipmb_dev *ipmb_dev = to_ipmb_dev(file); 157 __poll_t mask = EPOLLOUT; 158 159 mutex_lock(&ipmb_dev->file_mutex); 160 poll_wait(file, &ipmb_dev->wait_queue, wait); 161 162 if (atomic_read(&ipmb_dev->request_queue_len)) 163 mask |= EPOLLIN; 164 mutex_unlock(&ipmb_dev->file_mutex); 165 166 return mask; 167 } 168 169 static const struct file_operations ipmb_fops = { 170 .owner = THIS_MODULE, 171 .read = ipmb_read, 172 .write = ipmb_write, 173 .poll = ipmb_poll, 174 }; 175 176 /* Called with ipmb_dev->lock held. */ 177 static void ipmb_handle_request(struct ipmb_dev *ipmb_dev) 178 { 179 struct ipmb_request_elem *queue_elem; 180 181 if (atomic_read(&ipmb_dev->request_queue_len) >= 182 REQUEST_QUEUE_MAX_LEN) 183 return; 184 185 queue_elem = kmalloc(sizeof(*queue_elem), GFP_ATOMIC); 186 if (!queue_elem) 187 return; 188 189 memcpy(&queue_elem->request, &ipmb_dev->request, 190 sizeof(struct ipmb_msg)); 191 list_add(&queue_elem->list, &ipmb_dev->request_queue); 192 atomic_inc(&ipmb_dev->request_queue_len); 193 wake_up_all(&ipmb_dev->wait_queue); 194 } 195 196 static u8 ipmb_verify_checksum1(struct ipmb_dev *ipmb_dev, u8 rs_sa) 197 { 198 /* The 8 lsb of the sum is 0 when the checksum is valid */ 199 return (rs_sa + ipmb_dev->request.netfn_rs_lun + 200 ipmb_dev->request.checksum1); 201 } 202 203 /* 204 * Verify if message has proper ipmb header with minimum length 205 * and correct checksum byte. 206 */ 207 static bool is_ipmb_msg(struct ipmb_dev *ipmb_dev, u8 rs_sa) 208 { 209 if ((ipmb_dev->msg_idx >= IPMB_REQUEST_LEN_MIN) && 210 (!ipmb_verify_checksum1(ipmb_dev, rs_sa))) 211 return true; 212 213 return false; 214 } 215 216 /* 217 * The IPMB protocol only supports I2C Writes so there is no need 218 * to support I2C_SLAVE_READ* events. 219 * This i2c callback function only monitors IPMB request messages 220 * and adds them in a queue, so that they can be handled by 221 * receive_ipmb_request. 222 */ 223 static int ipmb_slave_cb(struct i2c_client *client, 224 enum i2c_slave_event event, u8 *val) 225 { 226 struct ipmb_dev *ipmb_dev = i2c_get_clientdata(client); 227 u8 *buf = (u8 *)&ipmb_dev->request; 228 unsigned long flags; 229 230 spin_lock_irqsave(&ipmb_dev->lock, flags); 231 switch (event) { 232 case I2C_SLAVE_WRITE_REQUESTED: 233 memset(&ipmb_dev->request, 0, sizeof(ipmb_dev->request)); 234 ipmb_dev->msg_idx = 0; 235 236 /* 237 * At index 0, ipmb_msg stores the length of msg, 238 * skip it for now. 239 * The len will be populated once the whole 240 * buf is populated. 241 * 242 * The I2C bus driver's responsibility is to pass the 243 * data bytes to the backend driver; it does not 244 * forward the i2c slave address. 245 * Since the first byte in the IPMB message is the 246 * address of the responder, it is the responsibility 247 * of the IPMB driver to format the message properly. 248 * So this driver prepends the address of the responder 249 * to the received i2c data before the request message 250 * is handled in userland. 251 */ 252 buf[++ipmb_dev->msg_idx] = GET_8BIT_ADDR(client->addr); 253 break; 254 255 case I2C_SLAVE_WRITE_RECEIVED: 256 if (ipmb_dev->msg_idx >= sizeof(struct ipmb_msg)) 257 break; 258 259 buf[++ipmb_dev->msg_idx] = *val; 260 break; 261 262 case I2C_SLAVE_STOP: 263 ipmb_dev->request.len = ipmb_dev->msg_idx; 264 if (is_ipmb_msg(ipmb_dev, GET_8BIT_ADDR(client->addr))) 265 ipmb_handle_request(ipmb_dev); 266 break; 267 268 default: 269 break; 270 } 271 spin_unlock_irqrestore(&ipmb_dev->lock, flags); 272 273 return 0; 274 } 275 276 static int ipmb_probe(struct i2c_client *client, 277 const struct i2c_device_id *id) 278 { 279 struct ipmb_dev *ipmb_dev; 280 int ret; 281 282 ipmb_dev = devm_kzalloc(&client->dev, sizeof(*ipmb_dev), 283 GFP_KERNEL); 284 if (!ipmb_dev) 285 return -ENOMEM; 286 287 spin_lock_init(&ipmb_dev->lock); 288 init_waitqueue_head(&ipmb_dev->wait_queue); 289 atomic_set(&ipmb_dev->request_queue_len, 0); 290 INIT_LIST_HEAD(&ipmb_dev->request_queue); 291 292 mutex_init(&ipmb_dev->file_mutex); 293 294 ipmb_dev->miscdev.minor = MISC_DYNAMIC_MINOR; 295 296 ipmb_dev->miscdev.name = devm_kasprintf(&client->dev, GFP_KERNEL, 297 "%s%d", "ipmb-", 298 client->adapter->nr); 299 ipmb_dev->miscdev.fops = &ipmb_fops; 300 ipmb_dev->miscdev.parent = &client->dev; 301 ret = misc_register(&ipmb_dev->miscdev); 302 if (ret) 303 return ret; 304 305 ipmb_dev->client = client; 306 i2c_set_clientdata(client, ipmb_dev); 307 ret = i2c_slave_register(client, ipmb_slave_cb); 308 if (ret) { 309 misc_deregister(&ipmb_dev->miscdev); 310 return ret; 311 } 312 313 return 0; 314 } 315 316 static int ipmb_remove(struct i2c_client *client) 317 { 318 struct ipmb_dev *ipmb_dev = i2c_get_clientdata(client); 319 320 i2c_slave_unregister(client); 321 misc_deregister(&ipmb_dev->miscdev); 322 323 return 0; 324 } 325 326 static const struct i2c_device_id ipmb_id[] = { 327 { "ipmb-dev", 0 }, 328 {}, 329 }; 330 MODULE_DEVICE_TABLE(i2c, ipmb_id); 331 332 static const struct acpi_device_id acpi_ipmb_id[] = { 333 { "IPMB0001", 0 }, 334 {}, 335 }; 336 MODULE_DEVICE_TABLE(acpi, acpi_ipmb_id); 337 338 static struct i2c_driver ipmb_driver = { 339 .driver = { 340 .name = "ipmb-dev", 341 .acpi_match_table = ACPI_PTR(acpi_ipmb_id), 342 }, 343 .probe = ipmb_probe, 344 .remove = ipmb_remove, 345 .id_table = ipmb_id, 346 }; 347 module_i2c_driver(ipmb_driver); 348 349 MODULE_AUTHOR("Mellanox Technologies"); 350 MODULE_DESCRIPTION("IPMB driver"); 351 MODULE_LICENSE("GPL v2"); 352