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 = (void *)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 = (void *)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 char *flags, int count) 300 { 301 struct nci_uart *nu = (void *)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 * file pointer to open file object for device 321 * cmd IOCTL command code 322 * arg argument for IOCTL call (cmd dependent) 323 * 324 * Return Value: Command dependent 325 */ 326 static int nci_uart_tty_ioctl(struct tty_struct *tty, struct file *file, 327 unsigned int cmd, unsigned long arg) 328 { 329 struct nci_uart *nu = (void *)tty->disc_data; 330 int err = 0; 331 332 switch (cmd) { 333 case NCIUARTSETDRIVER: 334 if (!nu) 335 return nci_uart_set_driver(tty, (unsigned int)arg); 336 else 337 return -EBUSY; 338 break; 339 default: 340 err = n_tty_ioctl_helper(tty, cmd, arg); 341 break; 342 } 343 344 return err; 345 } 346 347 /* We don't provide read/write/poll interface for user space. */ 348 static ssize_t nci_uart_tty_read(struct tty_struct *tty, struct file *file, 349 unsigned char *buf, size_t nr, 350 void **cookie, unsigned long offset) 351 { 352 return 0; 353 } 354 355 static ssize_t nci_uart_tty_write(struct tty_struct *tty, struct file *file, 356 const unsigned char *data, size_t count) 357 { 358 return 0; 359 } 360 361 static __poll_t nci_uart_tty_poll(struct tty_struct *tty, 362 struct file *filp, poll_table *wait) 363 { 364 return 0; 365 } 366 367 static int nci_uart_send(struct nci_uart *nu, struct sk_buff *skb) 368 { 369 /* Queue TX packet */ 370 skb_queue_tail(&nu->tx_q, skb); 371 372 /* Try to start TX (if possible) */ 373 nci_uart_tx_wakeup(nu); 374 375 return 0; 376 } 377 378 int nci_uart_register(struct nci_uart *nu) 379 { 380 if (!nu || !nu->ops.open || 381 !nu->ops.recv || !nu->ops.close) 382 return -EINVAL; 383 384 /* Set the send callback */ 385 nu->ops.send = nci_uart_send; 386 387 /* Add this driver in the driver list */ 388 if (nci_uart_drivers[nu->driver]) { 389 pr_err("driver %d is already registered\n", nu->driver); 390 return -EBUSY; 391 } 392 nci_uart_drivers[nu->driver] = nu; 393 394 pr_info("NCI uart driver '%s [%d]' registered\n", nu->name, nu->driver); 395 396 return 0; 397 } 398 EXPORT_SYMBOL_GPL(nci_uart_register); 399 400 void nci_uart_unregister(struct nci_uart *nu) 401 { 402 pr_info("NCI uart driver '%s [%d]' unregistered\n", nu->name, 403 nu->driver); 404 405 /* Remove this driver from the driver list */ 406 nci_uart_drivers[nu->driver] = NULL; 407 } 408 EXPORT_SYMBOL_GPL(nci_uart_unregister); 409 410 void nci_uart_set_config(struct nci_uart *nu, int baudrate, int flow_ctrl) 411 { 412 struct ktermios new_termios; 413 414 if (!nu->tty) 415 return; 416 417 down_read(&nu->tty->termios_rwsem); 418 new_termios = nu->tty->termios; 419 up_read(&nu->tty->termios_rwsem); 420 tty_termios_encode_baud_rate(&new_termios, baudrate, baudrate); 421 422 if (flow_ctrl) 423 new_termios.c_cflag |= CRTSCTS; 424 else 425 new_termios.c_cflag &= ~CRTSCTS; 426 427 tty_set_termios(nu->tty, &new_termios); 428 } 429 EXPORT_SYMBOL_GPL(nci_uart_set_config); 430 431 static struct tty_ldisc_ops nci_uart_ldisc = { 432 .owner = THIS_MODULE, 433 .num = N_NCI, 434 .name = "n_nci", 435 .open = nci_uart_tty_open, 436 .close = nci_uart_tty_close, 437 .read = nci_uart_tty_read, 438 .write = nci_uart_tty_write, 439 .poll = nci_uart_tty_poll, 440 .receive_buf = nci_uart_tty_receive, 441 .write_wakeup = nci_uart_tty_wakeup, 442 .ioctl = nci_uart_tty_ioctl, 443 .compat_ioctl = nci_uart_tty_ioctl, 444 }; 445 446 static int __init nci_uart_init(void) 447 { 448 return tty_register_ldisc(&nci_uart_ldisc); 449 } 450 451 static void __exit nci_uart_exit(void) 452 { 453 tty_unregister_ldisc(&nci_uart_ldisc); 454 } 455 456 module_init(nci_uart_init); 457 module_exit(nci_uart_exit); 458 459 MODULE_AUTHOR("Marvell International Ltd."); 460 MODULE_DESCRIPTION("NFC NCI UART driver"); 461 MODULE_LICENSE("GPL"); 462 MODULE_ALIAS_LDISC(N_NCI); 463