1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) ST-Ericsson AB 2010 4 * Author: Sjur Brendeland 5 */ 6 7 #include <linux/hardirq.h> 8 #include <linux/init.h> 9 #include <linux/module.h> 10 #include <linux/device.h> 11 #include <linux/types.h> 12 #include <linux/skbuff.h> 13 #include <linux/netdevice.h> 14 #include <linux/rtnetlink.h> 15 #include <linux/tty.h> 16 #include <linux/file.h> 17 #include <linux/if_arp.h> 18 #include <net/caif/caif_device.h> 19 #include <net/caif/cfcnfg.h> 20 #include <linux/err.h> 21 #include <linux/debugfs.h> 22 23 MODULE_LICENSE("GPL"); 24 MODULE_AUTHOR("Sjur Brendeland"); 25 MODULE_DESCRIPTION("CAIF serial device TTY line discipline"); 26 MODULE_LICENSE("GPL"); 27 MODULE_ALIAS_LDISC(N_CAIF); 28 29 #define SEND_QUEUE_LOW 10 30 #define SEND_QUEUE_HIGH 100 31 #define CAIF_SENDING 1 /* Bit 1 = 0x02*/ 32 #define CAIF_FLOW_OFF_SENT 4 /* Bit 4 = 0x10 */ 33 #define MAX_WRITE_CHUNK 4096 34 #define ON 1 35 #define OFF 0 36 #define CAIF_MAX_MTU 4096 37 38 static DEFINE_SPINLOCK(ser_lock); 39 static LIST_HEAD(ser_list); 40 static LIST_HEAD(ser_release_list); 41 42 static bool ser_loop; 43 module_param(ser_loop, bool, 0444); 44 MODULE_PARM_DESC(ser_loop, "Run in simulated loopback mode."); 45 46 static bool ser_use_stx = true; 47 module_param(ser_use_stx, bool, 0444); 48 MODULE_PARM_DESC(ser_use_stx, "STX enabled or not."); 49 50 static bool ser_use_fcs = true; 51 52 module_param(ser_use_fcs, bool, 0444); 53 MODULE_PARM_DESC(ser_use_fcs, "FCS enabled or not."); 54 55 static int ser_write_chunk = MAX_WRITE_CHUNK; 56 module_param(ser_write_chunk, int, 0444); 57 58 MODULE_PARM_DESC(ser_write_chunk, "Maximum size of data written to UART."); 59 60 static struct dentry *debugfsdir; 61 62 static int caif_net_open(struct net_device *dev); 63 static int caif_net_close(struct net_device *dev); 64 65 struct ser_device { 66 struct caif_dev_common common; 67 struct list_head node; 68 struct net_device *dev; 69 struct sk_buff_head head; 70 struct tty_struct *tty; 71 bool tx_started; 72 unsigned long state; 73 #ifdef CONFIG_DEBUG_FS 74 struct dentry *debugfs_tty_dir; 75 struct debugfs_blob_wrapper tx_blob; 76 struct debugfs_blob_wrapper rx_blob; 77 u8 rx_data[128]; 78 u8 tx_data[128]; 79 u8 tty_status; 80 81 #endif 82 }; 83 84 static void caifdev_setup(struct net_device *dev); 85 static void ldisc_tx_wakeup(struct tty_struct *tty); 86 #ifdef CONFIG_DEBUG_FS 87 static inline void update_tty_status(struct ser_device *ser) 88 { 89 ser->tty_status = 90 ser->tty->stopped << 5 | 91 ser->tty->flow_stopped << 3 | 92 ser->tty->packet << 2 | 93 ser->tty->port->low_latency << 1; 94 } 95 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty) 96 { 97 ser->debugfs_tty_dir = debugfs_create_dir(tty->name, debugfsdir); 98 99 debugfs_create_blob("last_tx_msg", 0400, ser->debugfs_tty_dir, 100 &ser->tx_blob); 101 102 debugfs_create_blob("last_rx_msg", 0400, ser->debugfs_tty_dir, 103 &ser->rx_blob); 104 105 debugfs_create_xul("ser_state", 0400, ser->debugfs_tty_dir, 106 &ser->state); 107 108 debugfs_create_x8("tty_status", 0400, ser->debugfs_tty_dir, 109 &ser->tty_status); 110 111 ser->tx_blob.data = ser->tx_data; 112 ser->tx_blob.size = 0; 113 ser->rx_blob.data = ser->rx_data; 114 ser->rx_blob.size = 0; 115 } 116 117 static inline void debugfs_deinit(struct ser_device *ser) 118 { 119 debugfs_remove_recursive(ser->debugfs_tty_dir); 120 } 121 122 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size) 123 { 124 if (size > sizeof(ser->rx_data)) 125 size = sizeof(ser->rx_data); 126 memcpy(ser->rx_data, data, size); 127 ser->rx_blob.data = ser->rx_data; 128 ser->rx_blob.size = size; 129 } 130 131 static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size) 132 { 133 if (size > sizeof(ser->tx_data)) 134 size = sizeof(ser->tx_data); 135 memcpy(ser->tx_data, data, size); 136 ser->tx_blob.data = ser->tx_data; 137 ser->tx_blob.size = size; 138 } 139 #else 140 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty) 141 { 142 } 143 144 static inline void debugfs_deinit(struct ser_device *ser) 145 { 146 } 147 148 static inline void update_tty_status(struct ser_device *ser) 149 { 150 } 151 152 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size) 153 { 154 } 155 156 static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size) 157 { 158 } 159 160 #endif 161 162 static void ldisc_receive(struct tty_struct *tty, const u8 *data, 163 char *flags, int count) 164 { 165 struct sk_buff *skb = NULL; 166 struct ser_device *ser; 167 int ret; 168 169 ser = tty->disc_data; 170 171 /* 172 * NOTE: flags may contain information about break or overrun. 173 * This is not yet handled. 174 */ 175 176 177 /* 178 * Workaround for garbage at start of transmission, 179 * only enable if STX handling is not enabled. 180 */ 181 if (!ser->common.use_stx && !ser->tx_started) { 182 dev_info(&ser->dev->dev, 183 "Bytes received before initial transmission -" 184 "bytes discarded.\n"); 185 return; 186 } 187 188 BUG_ON(ser->dev == NULL); 189 190 /* Get a suitable caif packet and copy in data. */ 191 skb = netdev_alloc_skb(ser->dev, count+1); 192 if (skb == NULL) 193 return; 194 skb_put_data(skb, data, count); 195 196 skb->protocol = htons(ETH_P_CAIF); 197 skb_reset_mac_header(skb); 198 debugfs_rx(ser, data, count); 199 /* Push received packet up the stack. */ 200 ret = netif_rx_ni(skb); 201 if (!ret) { 202 ser->dev->stats.rx_packets++; 203 ser->dev->stats.rx_bytes += count; 204 } else 205 ++ser->dev->stats.rx_dropped; 206 update_tty_status(ser); 207 } 208 209 static int handle_tx(struct ser_device *ser) 210 { 211 struct tty_struct *tty; 212 struct sk_buff *skb; 213 int tty_wr, len, room; 214 215 tty = ser->tty; 216 ser->tx_started = true; 217 218 /* Enter critical section */ 219 if (test_and_set_bit(CAIF_SENDING, &ser->state)) 220 return 0; 221 222 /* skb_peek is safe because handle_tx is called after skb_queue_tail */ 223 while ((skb = skb_peek(&ser->head)) != NULL) { 224 225 /* Make sure you don't write too much */ 226 len = skb->len; 227 room = tty_write_room(tty); 228 if (!room) 229 break; 230 if (room > ser_write_chunk) 231 room = ser_write_chunk; 232 if (len > room) 233 len = room; 234 235 /* Write to tty or loopback */ 236 if (!ser_loop) { 237 tty_wr = tty->ops->write(tty, skb->data, len); 238 update_tty_status(ser); 239 } else { 240 tty_wr = len; 241 ldisc_receive(tty, skb->data, NULL, len); 242 } 243 ser->dev->stats.tx_packets++; 244 ser->dev->stats.tx_bytes += tty_wr; 245 246 /* Error on TTY ?! */ 247 if (tty_wr < 0) 248 goto error; 249 /* Reduce buffer written, and discard if empty */ 250 skb_pull(skb, tty_wr); 251 if (skb->len == 0) { 252 struct sk_buff *tmp = skb_dequeue(&ser->head); 253 WARN_ON(tmp != skb); 254 dev_consume_skb_any(skb); 255 } 256 } 257 /* Send flow off if queue is empty */ 258 if (ser->head.qlen <= SEND_QUEUE_LOW && 259 test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) && 260 ser->common.flowctrl != NULL) 261 ser->common.flowctrl(ser->dev, ON); 262 clear_bit(CAIF_SENDING, &ser->state); 263 return 0; 264 error: 265 clear_bit(CAIF_SENDING, &ser->state); 266 return tty_wr; 267 } 268 269 static netdev_tx_t caif_xmit(struct sk_buff *skb, struct net_device *dev) 270 { 271 struct ser_device *ser; 272 273 if (WARN_ON(!dev)) 274 return -EINVAL; 275 276 ser = netdev_priv(dev); 277 278 /* Send flow off once, on high water mark */ 279 if (ser->head.qlen > SEND_QUEUE_HIGH && 280 !test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) && 281 ser->common.flowctrl != NULL) 282 283 ser->common.flowctrl(ser->dev, OFF); 284 285 skb_queue_tail(&ser->head, skb); 286 return handle_tx(ser); 287 } 288 289 290 static void ldisc_tx_wakeup(struct tty_struct *tty) 291 { 292 struct ser_device *ser; 293 294 ser = tty->disc_data; 295 BUG_ON(ser == NULL); 296 WARN_ON(ser->tty != tty); 297 handle_tx(ser); 298 } 299 300 301 static void ser_release(struct work_struct *work) 302 { 303 struct list_head list; 304 struct ser_device *ser, *tmp; 305 306 spin_lock(&ser_lock); 307 list_replace_init(&ser_release_list, &list); 308 spin_unlock(&ser_lock); 309 310 if (!list_empty(&list)) { 311 rtnl_lock(); 312 list_for_each_entry_safe(ser, tmp, &list, node) { 313 dev_close(ser->dev); 314 unregister_netdevice(ser->dev); 315 debugfs_deinit(ser); 316 } 317 rtnl_unlock(); 318 } 319 } 320 321 static DECLARE_WORK(ser_release_work, ser_release); 322 323 static int ldisc_open(struct tty_struct *tty) 324 { 325 struct ser_device *ser; 326 struct net_device *dev; 327 char name[64]; 328 int result; 329 330 /* No write no play */ 331 if (tty->ops->write == NULL) 332 return -EOPNOTSUPP; 333 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG)) 334 return -EPERM; 335 336 /* release devices to avoid name collision */ 337 ser_release(NULL); 338 339 result = snprintf(name, sizeof(name), "cf%s", tty->name); 340 if (result >= IFNAMSIZ) 341 return -EINVAL; 342 dev = alloc_netdev(sizeof(*ser), name, NET_NAME_UNKNOWN, 343 caifdev_setup); 344 if (!dev) 345 return -ENOMEM; 346 347 ser = netdev_priv(dev); 348 ser->tty = tty_kref_get(tty); 349 ser->dev = dev; 350 debugfs_init(ser, tty); 351 tty->receive_room = N_TTY_BUF_SIZE; 352 tty->disc_data = ser; 353 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); 354 rtnl_lock(); 355 result = register_netdevice(dev); 356 if (result) { 357 rtnl_unlock(); 358 free_netdev(dev); 359 return -ENODEV; 360 } 361 362 spin_lock(&ser_lock); 363 list_add(&ser->node, &ser_list); 364 spin_unlock(&ser_lock); 365 rtnl_unlock(); 366 netif_stop_queue(dev); 367 update_tty_status(ser); 368 return 0; 369 } 370 371 static void ldisc_close(struct tty_struct *tty) 372 { 373 struct ser_device *ser = tty->disc_data; 374 375 tty_kref_put(ser->tty); 376 377 spin_lock(&ser_lock); 378 list_move(&ser->node, &ser_release_list); 379 spin_unlock(&ser_lock); 380 schedule_work(&ser_release_work); 381 } 382 383 /* The line discipline structure. */ 384 static struct tty_ldisc_ops caif_ldisc = { 385 .owner = THIS_MODULE, 386 .magic = TTY_LDISC_MAGIC, 387 .name = "n_caif", 388 .open = ldisc_open, 389 .close = ldisc_close, 390 .receive_buf = ldisc_receive, 391 .write_wakeup = ldisc_tx_wakeup 392 }; 393 394 static int register_ldisc(void) 395 { 396 int result; 397 398 result = tty_register_ldisc(N_CAIF, &caif_ldisc); 399 if (result < 0) { 400 pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF, 401 result); 402 return result; 403 } 404 return result; 405 } 406 static const struct net_device_ops netdev_ops = { 407 .ndo_open = caif_net_open, 408 .ndo_stop = caif_net_close, 409 .ndo_start_xmit = caif_xmit 410 }; 411 412 static void caifdev_setup(struct net_device *dev) 413 { 414 struct ser_device *serdev = netdev_priv(dev); 415 416 dev->features = 0; 417 dev->netdev_ops = &netdev_ops; 418 dev->type = ARPHRD_CAIF; 419 dev->flags = IFF_POINTOPOINT | IFF_NOARP; 420 dev->mtu = CAIF_MAX_MTU; 421 dev->priv_flags |= IFF_NO_QUEUE; 422 dev->needs_free_netdev = true; 423 skb_queue_head_init(&serdev->head); 424 serdev->common.link_select = CAIF_LINK_LOW_LATENCY; 425 serdev->common.use_frag = true; 426 serdev->common.use_stx = ser_use_stx; 427 serdev->common.use_fcs = ser_use_fcs; 428 serdev->dev = dev; 429 } 430 431 432 static int caif_net_open(struct net_device *dev) 433 { 434 netif_wake_queue(dev); 435 return 0; 436 } 437 438 static int caif_net_close(struct net_device *dev) 439 { 440 netif_stop_queue(dev); 441 return 0; 442 } 443 444 static int __init caif_ser_init(void) 445 { 446 int ret; 447 448 ret = register_ldisc(); 449 debugfsdir = debugfs_create_dir("caif_serial", NULL); 450 return ret; 451 } 452 453 static void __exit caif_ser_exit(void) 454 { 455 spin_lock(&ser_lock); 456 list_splice(&ser_list, &ser_release_list); 457 spin_unlock(&ser_lock); 458 ser_release(NULL); 459 cancel_work_sync(&ser_release_work); 460 tty_unregister_ldisc(N_CAIF); 461 debugfs_remove_recursive(debugfsdir); 462 } 463 464 module_init(caif_ser_init); 465 module_exit(caif_ser_exit); 466