drivers/char/ipmi/ipmb_dev_int.c

   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         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
 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. */
 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
 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
 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  */
 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
 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
 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");