net/nfc/nci/uart.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright (C) 2015, Marvell International Ltd.
   4  *
   5  * Inspired (hugely) by HCI LDISC implementation in Bluetooth.
   6  *
   7  *  Copyright (C) 2000-2001  Qualcomm Incorporated
   8  *  Copyright (C) 2002-2003  Maxim Krasnyansky <maxk@qualcomm.com>
   9  *  Copyright (C) 2004-2005  Marcel Holtmann <marcel@holtmann.org>
  10  */
  11
  12 #include <linux/module.h>
  13
  14 #include <linux/kernel.h>
  15 #include <linux/init.h>
  16 #include <linux/types.h>
  17 #include <linux/fcntl.h>
  18 #include <linux/interrupt.h>
  19 #include <linux/ptrace.h>
  20 #include <linux/poll.h>
  21
  22 #include <linux/slab.h>
  23 #include <linux/tty.h>
  24 #include <linux/errno.h>
  25 #include <linux/string.h>
  26 #include <linux/signal.h>
  27 #include <linux/ioctl.h>
  28 #include <linux/skbuff.h>
  29
  30 #include <net/nfc/nci.h>
  31 #include <net/nfc/nci_core.h>
  32
  33 /* TX states  */
  34 #define NCI_UART_SENDING        1
  35 #define NCI_UART_TX_WAKEUP      2
  36
  37 static struct nci_uart *nci_uart_drivers[NCI_UART_DRIVER_MAX];
  38
  39 static inline struct sk_buff *nci_uart_dequeue(struct nci_uart *nu)
  40 {
  41         struct sk_buff *skb = nu->tx_skb;
  42
  43         if (!skb)
  44                 skb = skb_dequeue(&nu->tx_q);
  45         else
  46                 nu->tx_skb = NULL;
  47
  48         return skb;
  49 }
  50
  51 static inline int nci_uart_queue_empty(struct nci_uart *nu)
  52 {
  53         if (nu->tx_skb)
  54                 return 0;
  55
  56         return skb_queue_empty(&nu->tx_q);
  57 }
  58
  59 static int nci_uart_tx_wakeup(struct nci_uart *nu)
  60 {
  61         if (test_and_set_bit(NCI_UART_SENDING, &nu->tx_state)) {
  62                 set_bit(NCI_UART_TX_WAKEUP, &nu->tx_state);
  63                 return 0;
  64         }
  65
  66         schedule_work(&nu->write_work);
  67
  68         return 0;
  69 }
  70
  71 static void nci_uart_write_work(struct work_struct *work)
  72 {
  73         struct nci_uart *nu = container_of(work, struct nci_uart, write_work);
  74         struct tty_struct *tty = nu->tty;
  75         struct sk_buff *skb;
  76
  77 restart:
  78         clear_bit(NCI_UART_TX_WAKEUP, &nu->tx_state);
  79
  80         if (nu->ops.tx_start)
  81                 nu->ops.tx_start(nu);
  82
  83         while ((skb = nci_uart_dequeue(nu))) {
  84                 int len;
  85
  86                 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
  87                 len = tty->ops->write(tty, skb->data, skb->len);
  88                 skb_pull(skb, len);
  89                 if (skb->len) {
  90                         nu->tx_skb = skb;
  91                         break;
  92                 }
  93                 kfree_skb(skb);
  94         }
  95
  96         if (test_bit(NCI_UART_TX_WAKEUP, &nu->tx_state))
  97                 goto restart;
  98
  99         if (nu->ops.tx_done && nci_uart_queue_empty(nu))
 100                 nu->ops.tx_done(nu);
 101
 102         clear_bit(NCI_UART_SENDING, &nu->tx_state);
 103 }
 104
 105 static int nci_uart_set_driver(struct tty_struct *tty, unsigned int driver)
 106 {
 107         struct nci_uart *nu = NULL;
 108         int ret;
 109
 110         if (driver >= NCI_UART_DRIVER_MAX)
 111                 return -EINVAL;
 112
 113         if (!nci_uart_drivers[driver])
 114                 return -ENOENT;
 115
 116         nu = kzalloc(sizeof(*nu), GFP_KERNEL);
 117         if (!nu)
 118                 return -ENOMEM;
 119
 120         memcpy(nu, nci_uart_drivers[driver], sizeof(struct nci_uart));
 121         nu->tty = tty;
 122         tty->disc_data = nu;
 123         skb_queue_head_init(&nu->tx_q);
 124         INIT_WORK(&nu->write_work, nci_uart_write_work);
 125         spin_lock_init(&nu->rx_lock);
 126
 127         ret = nu->ops.open(nu);
 128         if (ret) {
 129                 tty->disc_data = NULL;
 130                 kfree(nu);
 131         } else if (!try_module_get(nu->owner)) {
 132                 nu->ops.close(nu);
 133                 tty->disc_data = NULL;
 134                 kfree(nu);
 135                 return -ENOENT;
 136         }
 137         return ret;
 138 }
 139
 140 /* ------ LDISC part ------ */
 141
 142 /* nci_uart_tty_open
 143  *
 144  *     Called when line discipline changed to NCI_UART.
 145  *
 146  * Arguments:
 147  *     tty    pointer to tty info structure
 148  * Return Value:
 149  *     0 if success, otherwise error code
 150  */
 151 static int nci_uart_tty_open(struct tty_struct *tty)
 152 {
 153         /* Error if the tty has no write op instead of leaving an exploitable
 154          * hole
 155          */
 156         if (!tty->ops->write)
 157                 return -EOPNOTSUPP;
 158
 159         tty->disc_data = NULL;
 160         tty->receive_room = 65536;
 161
 162         /* Flush any pending characters in the driver */
 163         tty_driver_flush_buffer(tty);
 164
 165         return 0;
 166 }
 167
 168 /* nci_uart_tty_close()
 169  *
 170  *    Called when the line discipline is changed to something
 171  *    else, the tty is closed, or the tty detects a hangup.
 172  */
 173 static void nci_uart_tty_close(struct tty_struct *tty)
 174 {
 175         struct nci_uart *nu = tty->disc_data;
 176
 177         /* Detach from the tty */
 178         tty->disc_data = NULL;
 179
 180         if (!nu)
 181                 return;
 182
 183         kfree_skb(nu->tx_skb);
 184         kfree_skb(nu->rx_skb);
 185
 186         skb_queue_purge(&nu->tx_q);
 187
 188         nu->ops.close(nu);
 189         nu->tty = NULL;
 190         module_put(nu->owner);
 191
 192         cancel_work_sync(&nu->write_work);
 193
 194         kfree(nu);
 195 }
 196
 197 /* nci_uart_tty_wakeup()
 198  *
 199  *    Callback for transmit wakeup. Called when low level
 200  *    device driver can accept more send data.
 201  *
 202  * Arguments:        tty    pointer to associated tty instance data
 203  * Return Value:    None
 204  */
 205 static void nci_uart_tty_wakeup(struct tty_struct *tty)
 206 {
 207         struct nci_uart *nu = tty->disc_data;
 208
 209         if (!nu)
 210                 return;
 211
 212         clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 213
 214         if (tty != nu->tty)
 215                 return;
 216
 217         nci_uart_tx_wakeup(nu);
 218 }
 219
 220 /* -- Default recv_buf handler --
 221  *
 222  * This handler supposes that NCI frames are sent over UART link without any
 223  * framing. It reads NCI header, retrieve the packet size and once all packet
 224  * bytes are received it passes it to nci_uart driver for processing.
 225  */
 226 static int nci_uart_default_recv_buf(struct nci_uart *nu, const u8 *data,
 227                                      int count)
 228 {
 229         int chunk_len;
 230
 231         if (!nu->ndev) {
 232                 nfc_err(nu->tty->dev,
 233                         "receive data from tty but no NCI dev is attached yet, drop buffer\n");
 234                 return 0;
 235         }
 236
 237         /* Decode all incoming data in packets
 238          * and enqueue then for processing.
 239          */
 240         while (count > 0) {
 241                 /* If this is the first data of a packet, allocate a buffer */
 242                 if (!nu->rx_skb) {
 243                         nu->rx_packet_len = -1;
 244                         nu->rx_skb = nci_skb_alloc(nu->ndev,
 245                                                    NCI_MAX_PACKET_SIZE,
 246                                                    GFP_ATOMIC);
 247                         if (!nu->rx_skb)
 248                                 return -ENOMEM;
 249                 }
 250
 251                 /* Eat byte after byte till full packet header is received */
 252                 if (nu->rx_skb->len < NCI_CTRL_HDR_SIZE) {
 253                         skb_put_u8(nu->rx_skb, *data++);
 254                         --count;
 255                         continue;
 256                 }
 257
 258                 /* Header was received but packet len was not read */
 259                 if (nu->rx_packet_len < 0)
 260                         nu->rx_packet_len = NCI_CTRL_HDR_SIZE +
 261                                 nci_plen(nu->rx_skb->data);
 262
 263                 /* Compute how many bytes are missing and how many bytes can
 264                  * be consumed.
 265                  */
 266                 chunk_len = nu->rx_packet_len - nu->rx_skb->len;
 267                 if (count < chunk_len)
 268                         chunk_len = count;
 269                 skb_put_data(nu->rx_skb, data, chunk_len);
 270                 data += chunk_len;
 271                 count -= chunk_len;
 272
 273                 /* Check if packet is fully received */
 274                 if (nu->rx_packet_len == nu->rx_skb->len) {
 275                         /* Pass RX packet to driver */
 276                         if (nu->ops.recv(nu, nu->rx_skb) != 0)
 277                                 nfc_err(nu->tty->dev, "corrupted RX packet\n");
 278                         /* Next packet will be a new one */
 279                         nu->rx_skb = NULL;
 280                 }
 281         }
 282
 283         return 0;
 284 }
 285
 286 /* nci_uart_tty_receive()
 287  *
 288  *     Called by tty low level driver when receive data is
 289  *     available.
 290  *
 291  * Arguments:  tty          pointer to tty instance data
 292  *             data         pointer to received data
 293  *             flags        pointer to flags for data
 294  *             count        count of received data in bytes
 295  *
 296  * Return Value:    None
 297  */
 298 static void nci_uart_tty_receive(struct tty_struct *tty, const u8 *data,
 299                                  const u8 *flags, size_t count)
 300 {
 301         struct nci_uart *nu = tty->disc_data;
 302
 303         if (!nu || tty != nu->tty)
 304                 return;
 305
 306         spin_lock(&nu->rx_lock);
 307         nci_uart_default_recv_buf(nu, data, count);
 308         spin_unlock(&nu->rx_lock);
 309
 310         tty_unthrottle(tty);
 311 }
 312
 313 /* nci_uart_tty_ioctl()
 314  *
 315  *    Process IOCTL system call for the tty device.
 316  *
 317  * Arguments:
 318  *
 319  *    tty        pointer to tty instance data
 320  *    cmd        IOCTL command code
 321  *    arg        argument for IOCTL call (cmd dependent)
 322  *
 323  * Return Value:    Command dependent
 324  */
 325 static int nci_uart_tty_ioctl(struct tty_struct *tty, unsigned int cmd,
 326                               unsigned long arg)
 327 {
 328         struct nci_uart *nu = tty->disc_data;
 329         int err = 0;
 330
 331         switch (cmd) {
 332         case NCIUARTSETDRIVER:
 333                 if (!nu)
 334                         return nci_uart_set_driver(tty, (unsigned int)arg);
 335                 else
 336                         return -EBUSY;
 337                 break;
 338         default:
 339                 err = n_tty_ioctl_helper(tty, cmd, arg);
 340                 break;
 341         }
 342
 343         return err;
 344 }
 345
 346 /* We don't provide read/write/poll interface for user space. */
 347 static ssize_t nci_uart_tty_read(struct tty_struct *tty, struct file *file,
 348                                  u8 *buf, size_t nr, void **cookie,
 349                                  unsigned long offset)
 350 {
 351         return 0;
 352 }
 353
 354 static ssize_t nci_uart_tty_write(struct tty_struct *tty, struct file *file,
 355                                   const u8 *data, size_t count)
 356 {
 357         return 0;
 358 }
 359
 360 static int nci_uart_send(struct nci_uart *nu, struct sk_buff *skb)
 361 {
 362         /* Queue TX packet */
 363         skb_queue_tail(&nu->tx_q, skb);
 364
 365         /* Try to start TX (if possible) */
 366         nci_uart_tx_wakeup(nu);
 367
 368         return 0;
 369 }
 370
 371 int nci_uart_register(struct nci_uart *nu)
 372 {
 373         if (!nu || !nu->ops.open ||
 374             !nu->ops.recv || !nu->ops.close)
 375                 return -EINVAL;
 376
 377         /* Set the send callback */
 378         nu->ops.send = nci_uart_send;
 379
 380         /* Add this driver in the driver list */
 381         if (nci_uart_drivers[nu->driver]) {
 382                 pr_err("driver %d is already registered\n", nu->driver);
 383                 return -EBUSY;
 384         }
 385         nci_uart_drivers[nu->driver] = nu;
 386
 387         pr_info("NCI uart driver '%s [%d]' registered\n", nu->name, nu->driver);
 388
 389         return 0;
 390 }
 391 EXPORT_SYMBOL_GPL(nci_uart_register);
 392
 393 void nci_uart_unregister(struct nci_uart *nu)
 394 {
 395         pr_info("NCI uart driver '%s [%d]' unregistered\n", nu->name,
 396                 nu->driver);
 397
 398         /* Remove this driver from the driver list */
 399         nci_uart_drivers[nu->driver] = NULL;
 400 }
 401 EXPORT_SYMBOL_GPL(nci_uart_unregister);
 402
 403 void nci_uart_set_config(struct nci_uart *nu, int baudrate, int flow_ctrl)
 404 {
 405         struct ktermios new_termios;
 406
 407         if (!nu->tty)
 408                 return;
 409
 410         down_read(&nu->tty->termios_rwsem);
 411         new_termios = nu->tty->termios;
 412         up_read(&nu->tty->termios_rwsem);
 413         tty_termios_encode_baud_rate(&new_termios, baudrate, baudrate);
 414
 415         if (flow_ctrl)
 416                 new_termios.c_cflag |= CRTSCTS;
 417         else
 418                 new_termios.c_cflag &= ~CRTSCTS;
 419
 420         tty_set_termios(nu->tty, &new_termios);
 421 }
 422 EXPORT_SYMBOL_GPL(nci_uart_set_config);
 423
 424 static struct tty_ldisc_ops nci_uart_ldisc = {
 425         .owner          = THIS_MODULE,
 426         .num            = N_NCI,
 427         .name           = "n_nci",
 428         .open           = nci_uart_tty_open,
 429         .close          = nci_uart_tty_close,
 430         .read           = nci_uart_tty_read,
 431         .write          = nci_uart_tty_write,
 432         .receive_buf    = nci_uart_tty_receive,
 433         .write_wakeup   = nci_uart_tty_wakeup,
 434         .ioctl          = nci_uart_tty_ioctl,
 435         .compat_ioctl   = nci_uart_tty_ioctl,
 436 };
 437
 438 static int __init nci_uart_init(void)
 439 {
 440         return tty_register_ldisc(&nci_uart_ldisc);
 441 }
 442
 443 static void __exit nci_uart_exit(void)
 444 {
 445         tty_unregister_ldisc(&nci_uart_ldisc);
 446 }
 447
 448 module_init(nci_uart_init);
 449 module_exit(nci_uart_exit);
 450
 451 MODULE_AUTHOR("Marvell International Ltd.");
 452 MODULE_DESCRIPTION("NFC NCI UART driver");
 453 MODULE_LICENSE("GPL");
 454 MODULE_ALIAS_LDISC(N_NCI);