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