net/nfc/nci/uart.c

   1 /*
   2  * Copyright (C) 2015, Marvell International Ltd.
   3  *
   4  * This software file (the "File") is distributed by Marvell International
   5  * Ltd. under the terms of the GNU General Public License Version 2, June 1991
   6  * (the "License").  You may use, redistribute and/or modify this File in
   7  * accordance with the terms and conditions of the License, a copy of which
   8  * is available on the worldwide web at
   9  * http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt.
  10  *
  11  * THE FILE IS DISTRIBUTED AS-IS, WITHOUT WARRANTY OF ANY KIND, AND THE
  12  * IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE
  13  * ARE EXPRESSLY DISCLAIMED.  The License provides additional details about
  14  * this warranty disclaimer.
  15  */
  16
  17 /* Inspired (hugely) by HCI LDISC implementation in Bluetooth.
  18  *
  19  *  Copyright (C) 2000-2001  Qualcomm Incorporated
  20  *  Copyright (C) 2002-2003  Maxim Krasnyansky <maxk@qualcomm.com>
  21  *  Copyright (C) 2004-2005  Marcel Holtmann <marcel@holtmann.org>
  22  */
  23
  24 #include <linux/module.h>
  25
  26 #include <linux/kernel.h>
  27 #include <linux/init.h>
  28 #include <linux/types.h>
  29 #include <linux/fcntl.h>
  30 #include <linux/interrupt.h>
  31 #include <linux/ptrace.h>
  32 #include <linux/poll.h>
  33
  34 #include <linux/slab.h>
  35 #include <linux/tty.h>
  36 #include <linux/errno.h>
  37 #include <linux/string.h>
  38 #include <linux/signal.h>
  39 #include <linux/ioctl.h>
  40 #include <linux/skbuff.h>
  41
  42 #include <net/nfc/nci.h>
  43 #include <net/nfc/nci_core.h>
  44
  45 /* TX states  */
  46 #define NCI_UART_SENDING        1
  47 #define NCI_UART_TX_WAKEUP      2
  48
  49 static struct nci_uart *nci_uart_drivers[NCI_UART_DRIVER_MAX];
  50
  51 static inline struct sk_buff *nci_uart_dequeue(struct nci_uart *nu)
  52 {
  53         struct sk_buff *skb = nu->tx_skb;
  54
  55         if (!skb)
  56                 skb = skb_dequeue(&nu->tx_q);
  57         else
  58                 nu->tx_skb = NULL;
  59
  60         return skb;
  61 }
  62
  63 static inline int nci_uart_queue_empty(struct nci_uart *nu)
  64 {
  65         if (nu->tx_skb)
  66                 return 0;
  67
  68         return skb_queue_empty(&nu->tx_q);
  69 }
  70
  71 static int nci_uart_tx_wakeup(struct nci_uart *nu)
  72 {
  73         if (test_and_set_bit(NCI_UART_SENDING, &nu->tx_state)) {
  74                 set_bit(NCI_UART_TX_WAKEUP, &nu->tx_state);
  75                 return 0;
  76         }
  77
  78         schedule_work(&nu->write_work);
  79
  80         return 0;
  81 }
  82
  83 static void nci_uart_write_work(struct work_struct *work)
  84 {
  85         struct nci_uart *nu = container_of(work, struct nci_uart, write_work);
  86         struct tty_struct *tty = nu->tty;
  87         struct sk_buff *skb;
  88
  89 restart:
  90         clear_bit(NCI_UART_TX_WAKEUP, &nu->tx_state);
  91
  92         if (nu->ops.tx_start)
  93                 nu->ops.tx_start(nu);
  94
  95         while ((skb = nci_uart_dequeue(nu))) {
  96                 int len;
  97
  98                 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
  99                 len = tty->ops->write(tty, skb->data, skb->len);
 100                 skb_pull(skb, len);
 101                 if (skb->len) {
 102                         nu->tx_skb = skb;
 103                         break;
 104                 }
 105                 kfree_skb(skb);
 106         }
 107
 108         if (test_bit(NCI_UART_TX_WAKEUP, &nu->tx_state))
 109                 goto restart;
 110
 111         if (nu->ops.tx_done && nci_uart_queue_empty(nu))
 112                 nu->ops.tx_done(nu);
 113
 114         clear_bit(NCI_UART_SENDING, &nu->tx_state);
 115 }
 116
 117 static int nci_uart_set_driver(struct tty_struct *tty, unsigned int driver)
 118 {
 119         struct nci_uart *nu = NULL;
 120         int ret;
 121
 122         if (driver >= NCI_UART_DRIVER_MAX)
 123                 return -EINVAL;
 124
 125         if (!nci_uart_drivers[driver])
 126                 return -ENOENT;
 127
 128         nu = kzalloc(sizeof(*nu), GFP_KERNEL);
 129         if (!nu)
 130                 return -ENOMEM;
 131
 132         memcpy(nu, nci_uart_drivers[driver], sizeof(struct nci_uart));
 133         nu->tty = tty;
 134         tty->disc_data = nu;
 135         skb_queue_head_init(&nu->tx_q);
 136         INIT_WORK(&nu->write_work, nci_uart_write_work);
 137         spin_lock_init(&nu->rx_lock);
 138
 139         ret = nu->ops.open(nu);
 140         if (ret) {
 141                 tty->disc_data = NULL;
 142                 kfree(nu);
 143         } else if (!try_module_get(nu->owner)) {
 144                 nu->ops.close(nu);
 145                 tty->disc_data = NULL;
 146                 kfree(nu);
 147                 return -ENOENT;
 148         }
 149         return ret;
 150 }
 151
 152 /* ------ LDISC part ------ */
 153
 154 /* nci_uart_tty_open
 155  *
 156  *     Called when line discipline changed to NCI_UART.
 157  *
 158  * Arguments:
 159  *     tty    pointer to tty info structure
 160  * Return Value:
 161  *     0 if success, otherwise error code
 162  */
 163 static int nci_uart_tty_open(struct tty_struct *tty)
 164 {
 165         /* Error if the tty has no write op instead of leaving an exploitable
 166          * hole
 167          */
 168         if (!tty->ops->write)
 169                 return -EOPNOTSUPP;
 170
 171         tty->disc_data = NULL;
 172         tty->receive_room = 65536;
 173
 174         /* Flush any pending characters in the driver */
 175         tty_driver_flush_buffer(tty);
 176
 177         return 0;
 178 }
 179
 180 /* nci_uart_tty_close()
 181  *
 182  *    Called when the line discipline is changed to something
 183  *    else, the tty is closed, or the tty detects a hangup.
 184  */
 185 static void nci_uart_tty_close(struct tty_struct *tty)
 186 {
 187         struct nci_uart *nu = (void *)tty->disc_data;
 188
 189         /* Detach from the tty */
 190         tty->disc_data = NULL;
 191
 192         if (!nu)
 193                 return;
 194
 195         if (nu->tx_skb)
 196                 kfree_skb(nu->tx_skb);
 197         if (nu->rx_skb)
 198                 kfree_skb(nu->rx_skb);
 199
 200         skb_queue_purge(&nu->tx_q);
 201
 202         nu->ops.close(nu);
 203         nu->tty = NULL;
 204         module_put(nu->owner);
 205
 206         cancel_work_sync(&nu->write_work);
 207
 208         kfree(nu);
 209 }
 210
 211 /* nci_uart_tty_wakeup()
 212  *
 213  *    Callback for transmit wakeup. Called when low level
 214  *    device driver can accept more send data.
 215  *
 216  * Arguments:        tty    pointer to associated tty instance data
 217  * Return Value:    None
 218  */
 219 static void nci_uart_tty_wakeup(struct tty_struct *tty)
 220 {
 221         struct nci_uart *nu = (void *)tty->disc_data;
 222
 223         if (!nu)
 224                 return;
 225
 226         clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 227
 228         if (tty != nu->tty)
 229                 return;
 230
 231         nci_uart_tx_wakeup(nu);
 232 }
 233
 234 /* nci_uart_tty_receive()
 235  *
 236  *     Called by tty low level driver when receive data is
 237  *     available.
 238  *
 239  * Arguments:  tty          pointer to tty isntance data
 240  *             data         pointer to received data
 241  *             flags        pointer to flags for data
 242  *             count        count of received data in bytes
 243  *
 244  * Return Value:    None
 245  */
 246 static void nci_uart_tty_receive(struct tty_struct *tty, const u8 *data,
 247                                  char *flags, int count)
 248 {
 249         struct nci_uart *nu = (void *)tty->disc_data;
 250
 251         if (!nu || tty != nu->tty)
 252                 return;
 253
 254         spin_lock(&nu->rx_lock);
 255         nu->ops.recv_buf(nu, (void *)data, flags, count);
 256         spin_unlock(&nu->rx_lock);
 257
 258         tty_unthrottle(tty);
 259 }
 260
 261 /* nci_uart_tty_ioctl()
 262  *
 263  *    Process IOCTL system call for the tty device.
 264  *
 265  * Arguments:
 266  *
 267  *    tty        pointer to tty instance data
 268  *    file       pointer to open file object for device
 269  *    cmd        IOCTL command code
 270  *    arg        argument for IOCTL call (cmd dependent)
 271  *
 272  * Return Value:    Command dependent
 273  */
 274 static int nci_uart_tty_ioctl(struct tty_struct *tty, struct file *file,
 275                               unsigned int cmd, unsigned long arg)
 276 {
 277         struct nci_uart *nu = (void *)tty->disc_data;
 278         int err = 0;
 279
 280         switch (cmd) {
 281         case NCIUARTSETDRIVER:
 282                 if (!nu)
 283                         return nci_uart_set_driver(tty, (unsigned int)arg);
 284                 else
 285                         return -EBUSY;
 286                 break;
 287         default:
 288                 err = n_tty_ioctl_helper(tty, file, cmd, arg);
 289                 break;
 290         }
 291
 292         return err;
 293 }
 294
 295 /* We don't provide read/write/poll interface for user space. */
 296 static ssize_t nci_uart_tty_read(struct tty_struct *tty, struct file *file,
 297                                  unsigned char __user *buf, size_t nr)
 298 {
 299         return 0;
 300 }
 301
 302 static ssize_t nci_uart_tty_write(struct tty_struct *tty, struct file *file,
 303                                   const unsigned char *data, size_t count)
 304 {
 305         return 0;
 306 }
 307
 308 static unsigned int nci_uart_tty_poll(struct tty_struct *tty,
 309                                       struct file *filp, poll_table *wait)
 310 {
 311         return 0;
 312 }
 313
 314 static int nci_uart_send(struct nci_uart *nu, struct sk_buff *skb)
 315 {
 316         /* Queue TX packet */
 317         skb_queue_tail(&nu->tx_q, skb);
 318
 319         /* Try to start TX (if possible) */
 320         nci_uart_tx_wakeup(nu);
 321
 322         return 0;
 323 }
 324
 325 /* -- Default recv_buf handler --
 326  *
 327  * This handler supposes that NCI frames are sent over UART link without any
 328  * framing. It reads NCI header, retrieve the packet size and once all packet
 329  * bytes are received it passes it to nci_uart driver for processing.
 330  */
 331 static int nci_uart_default_recv_buf(struct nci_uart *nu, const u8 *data,
 332                                      char *flags, int count)
 333 {
 334         int chunk_len;
 335
 336         if (!nu->ndev) {
 337                 nfc_err(nu->tty->dev,
 338                         "receive data from tty but no NCI dev is attached yet, drop buffer\n");
 339                 return 0;
 340         }
 341
 342         /* Decode all incoming data in packets
 343          * and enqueue then for processing.
 344          */
 345         while (count > 0) {
 346                 /* If this is the first data of a packet, allocate a buffer */
 347                 if (!nu->rx_skb) {
 348                         nu->rx_packet_len = -1;
 349                         nu->rx_skb = nci_skb_alloc(nu->ndev,
 350                                                    NCI_MAX_PACKET_SIZE,
 351                                                    GFP_KERNEL);
 352                         if (!nu->rx_skb)
 353                                 return -ENOMEM;
 354                 }
 355
 356                 /* Eat byte after byte till full packet header is received */
 357                 if (nu->rx_skb->len < NCI_CTRL_HDR_SIZE) {
 358                         *skb_put(nu->rx_skb, 1) = *data++;
 359                         --count;
 360                         continue;
 361                 }
 362
 363                 /* Header was received but packet len was not read */
 364                 if (nu->rx_packet_len < 0)
 365                         nu->rx_packet_len = NCI_CTRL_HDR_SIZE +
 366                                 nci_plen(nu->rx_skb->data);
 367
 368                 /* Compute how many bytes are missing and how many bytes can
 369                  * be consumed.
 370                  */
 371                 chunk_len = nu->rx_packet_len - nu->rx_skb->len;
 372                 if (count < chunk_len)
 373                         chunk_len = count;
 374                 memcpy(skb_put(nu->rx_skb, chunk_len), data, chunk_len);
 375                 data += chunk_len;
 376                 count -= chunk_len;
 377
 378                 /* Chcek if packet is fully received */
 379                 if (nu->rx_packet_len == nu->rx_skb->len) {
 380                         /* Pass RX packet to driver */
 381                         if (nu->ops.recv(nu, nu->rx_skb) != 0)
 382                                 nfc_err(nu->tty->dev, "corrupted RX packet\n");
 383                         /* Next packet will be a new one */
 384                         nu->rx_skb = NULL;
 385                 }
 386         }
 387
 388         return 0;
 389 }
 390
 391 /* -- Default recv handler -- */
 392 static int nci_uart_default_recv(struct nci_uart *nu, struct sk_buff *skb)
 393 {
 394         return nci_recv_frame(nu->ndev, skb);
 395 }
 396
 397 int nci_uart_register(struct nci_uart *nu)
 398 {
 399         if (!nu || !nu->ops.open ||
 400             !nu->ops.recv || !nu->ops.close)
 401                 return -EINVAL;
 402
 403         /* Set the send callback */
 404         nu->ops.send = nci_uart_send;
 405
 406         /* Install default handlers if not overridden */
 407         if (!nu->ops.recv_buf)
 408                 nu->ops.recv_buf = nci_uart_default_recv_buf;
 409         if (!nu->ops.recv)
 410                 nu->ops.recv = nci_uart_default_recv;
 411
 412         /* Add this driver in the driver list */
 413         if (nci_uart_drivers[nu->driver]) {
 414                 pr_err("driver %d is already registered\n", nu->driver);
 415                 return -EBUSY;
 416         }
 417         nci_uart_drivers[nu->driver] = nu;
 418
 419         pr_info("NCI uart driver '%s [%d]' registered\n", nu->name, nu->driver);
 420
 421         return 0;
 422 }
 423 EXPORT_SYMBOL_GPL(nci_uart_register);
 424
 425 void nci_uart_unregister(struct nci_uart *nu)
 426 {
 427         pr_info("NCI uart driver '%s [%d]' unregistered\n", nu->name,
 428                 nu->driver);
 429
 430         /* Remove this driver from the driver list */
 431         nci_uart_drivers[nu->driver] = NULL;
 432 }
 433 EXPORT_SYMBOL_GPL(nci_uart_unregister);
 434
 435 void nci_uart_set_config(struct nci_uart *nu, int baudrate, int flow_ctrl)
 436 {
 437         struct ktermios new_termios;
 438
 439         if (!nu->tty)
 440                 return;
 441
 442         down_read(&nu->tty->termios_rwsem);
 443         new_termios = nu->tty->termios;
 444         up_read(&nu->tty->termios_rwsem);
 445         tty_termios_encode_baud_rate(&new_termios, baudrate, baudrate);
 446
 447         if (flow_ctrl)
 448                 new_termios.c_cflag |= CRTSCTS;
 449         else
 450                 new_termios.c_cflag &= ~CRTSCTS;
 451
 452         tty_set_termios(nu->tty, &new_termios);
 453 }
 454 EXPORT_SYMBOL_GPL(nci_uart_set_config);
 455
 456 static struct tty_ldisc_ops nci_uart_ldisc = {
 457         .magic          = TTY_LDISC_MAGIC,
 458         .owner          = THIS_MODULE,
 459         .name           = "n_nci",
 460         .open           = nci_uart_tty_open,
 461         .close          = nci_uart_tty_close,
 462         .read           = nci_uart_tty_read,
 463         .write          = nci_uart_tty_write,
 464         .poll           = nci_uart_tty_poll,
 465         .receive_buf    = nci_uart_tty_receive,
 466         .write_wakeup   = nci_uart_tty_wakeup,
 467         .ioctl          = nci_uart_tty_ioctl,
 468 };
 469
 470 static int __init nci_uart_init(void)
 471 {
 472         memset(nci_uart_drivers, 0, sizeof(nci_uart_drivers));
 473         return tty_register_ldisc(N_NCI, &nci_uart_ldisc);
 474 }
 475
 476 static void __exit nci_uart_exit(void)
 477 {
 478         tty_unregister_ldisc(N_NCI);
 479 }
 480
 481 module_init(nci_uart_init);
 482 module_exit(nci_uart_exit);
 483
 484 MODULE_AUTHOR("Marvell International Ltd.");
 485 MODULE_DESCRIPTION("NFC NCI UART driver");
 486 MODULE_LICENSE("GPL");
 487 MODULE_ALIAS_LDISC(N_NCI);