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 = 98 debugfs_create_dir(tty->name, debugfsdir); 99 if (!IS_ERR(ser->debugfs_tty_dir)) { 100 debugfs_create_blob("last_tx_msg", 0400, 101 ser->debugfs_tty_dir, 102 &ser->tx_blob); 103 104 debugfs_create_blob("last_rx_msg", 0400, 105 ser->debugfs_tty_dir, 106 &ser->rx_blob); 107 108 debugfs_create_x32("ser_state", 0400, 109 ser->debugfs_tty_dir, 110 (u32 *)&ser->state); 111 112 debugfs_create_x8("tty_status", 0400, 113 ser->debugfs_tty_dir, 114 &ser->tty_status); 115 116 } 117 ser->tx_blob.data = ser->tx_data; 118 ser->tx_blob.size = 0; 119 ser->rx_blob.data = ser->rx_data; 120 ser->rx_blob.size = 0; 121 } 122 123 static inline void debugfs_deinit(struct ser_device *ser) 124 { 125 debugfs_remove_recursive(ser->debugfs_tty_dir); 126 } 127 128 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size) 129 { 130 if (size > sizeof(ser->rx_data)) 131 size = sizeof(ser->rx_data); 132 memcpy(ser->rx_data, data, size); 133 ser->rx_blob.data = ser->rx_data; 134 ser->rx_blob.size = size; 135 } 136 137 static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size) 138 { 139 if (size > sizeof(ser->tx_data)) 140 size = sizeof(ser->tx_data); 141 memcpy(ser->tx_data, data, size); 142 ser->tx_blob.data = ser->tx_data; 143 ser->tx_blob.size = size; 144 } 145 #else 146 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty) 147 { 148 } 149 150 static inline void debugfs_deinit(struct ser_device *ser) 151 { 152 } 153 154 static inline void update_tty_status(struct ser_device *ser) 155 { 156 } 157 158 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size) 159 { 160 } 161 162 static inline void debugfs_tx(struct ser_device *ser, const u8 *data, int size) 163 { 164 } 165 166 #endif 167 168 static void ldisc_receive(struct tty_struct *tty, const u8 *data, 169 char *flags, int count) 170 { 171 struct sk_buff *skb = NULL; 172 struct ser_device *ser; 173 int ret; 174 175 ser = tty->disc_data; 176 177 /* 178 * NOTE: flags may contain information about break or overrun. 179 * This is not yet handled. 180 */ 181 182 183 /* 184 * Workaround for garbage at start of transmission, 185 * only enable if STX handling is not enabled. 186 */ 187 if (!ser->common.use_stx && !ser->tx_started) { 188 dev_info(&ser->dev->dev, 189 "Bytes received before initial transmission -" 190 "bytes discarded.\n"); 191 return; 192 } 193 194 BUG_ON(ser->dev == NULL); 195 196 /* Get a suitable caif packet and copy in data. */ 197 skb = netdev_alloc_skb(ser->dev, count+1); 198 if (skb == NULL) 199 return; 200 skb_put_data(skb, data, count); 201 202 skb->protocol = htons(ETH_P_CAIF); 203 skb_reset_mac_header(skb); 204 debugfs_rx(ser, data, count); 205 /* Push received packet up the stack. */ 206 ret = netif_rx_ni(skb); 207 if (!ret) { 208 ser->dev->stats.rx_packets++; 209 ser->dev->stats.rx_bytes += count; 210 } else 211 ++ser->dev->stats.rx_dropped; 212 update_tty_status(ser); 213 } 214 215 static int handle_tx(struct ser_device *ser) 216 { 217 struct tty_struct *tty; 218 struct sk_buff *skb; 219 int tty_wr, len, room; 220 221 tty = ser->tty; 222 ser->tx_started = true; 223 224 /* Enter critical section */ 225 if (test_and_set_bit(CAIF_SENDING, &ser->state)) 226 return 0; 227 228 /* skb_peek is safe because handle_tx is called after skb_queue_tail */ 229 while ((skb = skb_peek(&ser->head)) != NULL) { 230 231 /* Make sure you don't write too much */ 232 len = skb->len; 233 room = tty_write_room(tty); 234 if (!room) 235 break; 236 if (room > ser_write_chunk) 237 room = ser_write_chunk; 238 if (len > room) 239 len = room; 240 241 /* Write to tty or loopback */ 242 if (!ser_loop) { 243 tty_wr = tty->ops->write(tty, skb->data, len); 244 update_tty_status(ser); 245 } else { 246 tty_wr = len; 247 ldisc_receive(tty, skb->data, NULL, len); 248 } 249 ser->dev->stats.tx_packets++; 250 ser->dev->stats.tx_bytes += tty_wr; 251 252 /* Error on TTY ?! */ 253 if (tty_wr < 0) 254 goto error; 255 /* Reduce buffer written, and discard if empty */ 256 skb_pull(skb, tty_wr); 257 if (skb->len == 0) { 258 struct sk_buff *tmp = skb_dequeue(&ser->head); 259 WARN_ON(tmp != skb); 260 dev_consume_skb_any(skb); 261 } 262 } 263 /* Send flow off if queue is empty */ 264 if (ser->head.qlen <= SEND_QUEUE_LOW && 265 test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) && 266 ser->common.flowctrl != NULL) 267 ser->common.flowctrl(ser->dev, ON); 268 clear_bit(CAIF_SENDING, &ser->state); 269 return 0; 270 error: 271 clear_bit(CAIF_SENDING, &ser->state); 272 return tty_wr; 273 } 274 275 static int caif_xmit(struct sk_buff *skb, struct net_device *dev) 276 { 277 struct ser_device *ser; 278 279 BUG_ON(dev == NULL); 280 ser = netdev_priv(dev); 281 282 /* Send flow off once, on high water mark */ 283 if (ser->head.qlen > SEND_QUEUE_HIGH && 284 !test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) && 285 ser->common.flowctrl != NULL) 286 287 ser->common.flowctrl(ser->dev, OFF); 288 289 skb_queue_tail(&ser->head, skb); 290 return handle_tx(ser); 291 } 292 293 294 static void ldisc_tx_wakeup(struct tty_struct *tty) 295 { 296 struct ser_device *ser; 297 298 ser = tty->disc_data; 299 BUG_ON(ser == NULL); 300 WARN_ON(ser->tty != tty); 301 handle_tx(ser); 302 } 303 304 305 static void ser_release(struct work_struct *work) 306 { 307 struct list_head list; 308 struct ser_device *ser, *tmp; 309 310 spin_lock(&ser_lock); 311 list_replace_init(&ser_release_list, &list); 312 spin_unlock(&ser_lock); 313 314 if (!list_empty(&list)) { 315 rtnl_lock(); 316 list_for_each_entry_safe(ser, tmp, &list, node) { 317 dev_close(ser->dev); 318 unregister_netdevice(ser->dev); 319 debugfs_deinit(ser); 320 } 321 rtnl_unlock(); 322 } 323 } 324 325 static DECLARE_WORK(ser_release_work, ser_release); 326 327 static int ldisc_open(struct tty_struct *tty) 328 { 329 struct ser_device *ser; 330 struct net_device *dev; 331 char name[64]; 332 int result; 333 334 /* No write no play */ 335 if (tty->ops->write == NULL) 336 return -EOPNOTSUPP; 337 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG)) 338 return -EPERM; 339 340 /* release devices to avoid name collision */ 341 ser_release(NULL); 342 343 result = snprintf(name, sizeof(name), "cf%s", tty->name); 344 if (result >= IFNAMSIZ) 345 return -EINVAL; 346 dev = alloc_netdev(sizeof(*ser), name, NET_NAME_UNKNOWN, 347 caifdev_setup); 348 if (!dev) 349 return -ENOMEM; 350 351 ser = netdev_priv(dev); 352 ser->tty = tty_kref_get(tty); 353 ser->dev = dev; 354 debugfs_init(ser, tty); 355 tty->receive_room = N_TTY_BUF_SIZE; 356 tty->disc_data = ser; 357 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); 358 rtnl_lock(); 359 result = register_netdevice(dev); 360 if (result) { 361 rtnl_unlock(); 362 free_netdev(dev); 363 return -ENODEV; 364 } 365 366 spin_lock(&ser_lock); 367 list_add(&ser->node, &ser_list); 368 spin_unlock(&ser_lock); 369 rtnl_unlock(); 370 netif_stop_queue(dev); 371 update_tty_status(ser); 372 return 0; 373 } 374 375 static void ldisc_close(struct tty_struct *tty) 376 { 377 struct ser_device *ser = tty->disc_data; 378 379 tty_kref_put(ser->tty); 380 381 spin_lock(&ser_lock); 382 list_move(&ser->node, &ser_release_list); 383 spin_unlock(&ser_lock); 384 schedule_work(&ser_release_work); 385 } 386 387 /* The line discipline structure. */ 388 static struct tty_ldisc_ops caif_ldisc = { 389 .owner = THIS_MODULE, 390 .magic = TTY_LDISC_MAGIC, 391 .name = "n_caif", 392 .open = ldisc_open, 393 .close = ldisc_close, 394 .receive_buf = ldisc_receive, 395 .write_wakeup = ldisc_tx_wakeup 396 }; 397 398 static int register_ldisc(void) 399 { 400 int result; 401 402 result = tty_register_ldisc(N_CAIF, &caif_ldisc); 403 if (result < 0) { 404 pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF, 405 result); 406 return result; 407 } 408 return result; 409 } 410 static const struct net_device_ops netdev_ops = { 411 .ndo_open = caif_net_open, 412 .ndo_stop = caif_net_close, 413 .ndo_start_xmit = caif_xmit 414 }; 415 416 static void caifdev_setup(struct net_device *dev) 417 { 418 struct ser_device *serdev = netdev_priv(dev); 419 420 dev->features = 0; 421 dev->netdev_ops = &netdev_ops; 422 dev->type = ARPHRD_CAIF; 423 dev->flags = IFF_POINTOPOINT | IFF_NOARP; 424 dev->mtu = CAIF_MAX_MTU; 425 dev->priv_flags |= IFF_NO_QUEUE; 426 dev->needs_free_netdev = true; 427 skb_queue_head_init(&serdev->head); 428 serdev->common.link_select = CAIF_LINK_LOW_LATENCY; 429 serdev->common.use_frag = true; 430 serdev->common.use_stx = ser_use_stx; 431 serdev->common.use_fcs = ser_use_fcs; 432 serdev->dev = dev; 433 } 434 435 436 static int caif_net_open(struct net_device *dev) 437 { 438 netif_wake_queue(dev); 439 return 0; 440 } 441 442 static int caif_net_close(struct net_device *dev) 443 { 444 netif_stop_queue(dev); 445 return 0; 446 } 447 448 static int __init caif_ser_init(void) 449 { 450 int ret; 451 452 ret = register_ldisc(); 453 debugfsdir = debugfs_create_dir("caif_serial", NULL); 454 return ret; 455 } 456 457 static void __exit caif_ser_exit(void) 458 { 459 spin_lock(&ser_lock); 460 list_splice(&ser_list, &ser_release_list); 461 spin_unlock(&ser_lock); 462 ser_release(NULL); 463 cancel_work_sync(&ser_release_work); 464 tty_unregister_ldisc(N_CAIF); 465 debugfs_remove_recursive(debugfsdir); 466 } 467 468 module_init(caif_ser_init); 469 module_exit(caif_ser_exit); 470