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 #else 130 static inline void debugfs_init(struct ser_device *ser, struct tty_struct *tty) 131 { 132 } 133 134 static inline void debugfs_deinit(struct ser_device *ser) 135 { 136 } 137 138 static inline void update_tty_status(struct ser_device *ser) 139 { 140 } 141 142 static inline void debugfs_rx(struct ser_device *ser, const u8 *data, int size) 143 { 144 } 145 #endif 146 147 static void ldisc_receive(struct tty_struct *tty, const u8 *data, 148 const u8 *flags, size_t count) 149 { 150 struct sk_buff *skb = NULL; 151 struct ser_device *ser; 152 int ret; 153 154 ser = tty->disc_data; 155 156 /* 157 * NOTE: flags may contain information about break or overrun. 158 * This is not yet handled. 159 */ 160 161 162 /* 163 * Workaround for garbage at start of transmission, 164 * only enable if STX handling is not enabled. 165 */ 166 if (!ser->common.use_stx && !ser->tx_started) { 167 dev_info(&ser->dev->dev, 168 "Bytes received before initial transmission -" 169 "bytes discarded.\n"); 170 return; 171 } 172 173 BUG_ON(ser->dev == NULL); 174 175 /* Get a suitable caif packet and copy in data. */ 176 skb = netdev_alloc_skb(ser->dev, count+1); 177 if (skb == NULL) 178 return; 179 skb_put_data(skb, data, count); 180 181 skb->protocol = htons(ETH_P_CAIF); 182 skb_reset_mac_header(skb); 183 debugfs_rx(ser, data, count); 184 /* Push received packet up the stack. */ 185 ret = netif_rx(skb); 186 if (!ret) { 187 ser->dev->stats.rx_packets++; 188 ser->dev->stats.rx_bytes += count; 189 } else 190 ++ser->dev->stats.rx_dropped; 191 update_tty_status(ser); 192 } 193 194 static int handle_tx(struct ser_device *ser) 195 { 196 struct tty_struct *tty; 197 struct sk_buff *skb; 198 int tty_wr, len, room; 199 200 tty = ser->tty; 201 ser->tx_started = true; 202 203 /* Enter critical section */ 204 if (test_and_set_bit(CAIF_SENDING, &ser->state)) 205 return 0; 206 207 /* skb_peek is safe because handle_tx is called after skb_queue_tail */ 208 while ((skb = skb_peek(&ser->head)) != NULL) { 209 210 /* Make sure you don't write too much */ 211 len = skb->len; 212 room = tty_write_room(tty); 213 if (!room) 214 break; 215 if (room > ser_write_chunk) 216 room = ser_write_chunk; 217 if (len > room) 218 len = room; 219 220 /* Write to tty or loopback */ 221 if (!ser_loop) { 222 tty_wr = tty->ops->write(tty, skb->data, len); 223 update_tty_status(ser); 224 } else { 225 tty_wr = len; 226 ldisc_receive(tty, skb->data, NULL, len); 227 } 228 ser->dev->stats.tx_packets++; 229 ser->dev->stats.tx_bytes += tty_wr; 230 231 /* Error on TTY ?! */ 232 if (tty_wr < 0) 233 goto error; 234 /* Reduce buffer written, and discard if empty */ 235 skb_pull(skb, tty_wr); 236 if (skb->len == 0) { 237 struct sk_buff *tmp = skb_dequeue(&ser->head); 238 WARN_ON(tmp != skb); 239 dev_consume_skb_any(skb); 240 } 241 } 242 /* Send flow off if queue is empty */ 243 if (ser->head.qlen <= SEND_QUEUE_LOW && 244 test_and_clear_bit(CAIF_FLOW_OFF_SENT, &ser->state) && 245 ser->common.flowctrl != NULL) 246 ser->common.flowctrl(ser->dev, ON); 247 clear_bit(CAIF_SENDING, &ser->state); 248 return 0; 249 error: 250 clear_bit(CAIF_SENDING, &ser->state); 251 return tty_wr; 252 } 253 254 static netdev_tx_t caif_xmit(struct sk_buff *skb, struct net_device *dev) 255 { 256 struct ser_device *ser; 257 258 ser = netdev_priv(dev); 259 260 /* Send flow off once, on high water mark */ 261 if (ser->head.qlen > SEND_QUEUE_HIGH && 262 !test_and_set_bit(CAIF_FLOW_OFF_SENT, &ser->state) && 263 ser->common.flowctrl != NULL) 264 265 ser->common.flowctrl(ser->dev, OFF); 266 267 skb_queue_tail(&ser->head, skb); 268 return handle_tx(ser); 269 } 270 271 272 static void ldisc_tx_wakeup(struct tty_struct *tty) 273 { 274 struct ser_device *ser; 275 276 ser = tty->disc_data; 277 BUG_ON(ser == NULL); 278 WARN_ON(ser->tty != tty); 279 handle_tx(ser); 280 } 281 282 283 static void ser_release(struct work_struct *work) 284 { 285 struct list_head list; 286 struct ser_device *ser, *tmp; 287 struct tty_struct *tty; 288 289 spin_lock(&ser_lock); 290 list_replace_init(&ser_release_list, &list); 291 spin_unlock(&ser_lock); 292 293 if (!list_empty(&list)) { 294 rtnl_lock(); 295 list_for_each_entry_safe(ser, tmp, &list, node) { 296 tty = ser->tty; 297 dev_close(ser->dev); 298 unregister_netdevice(ser->dev); 299 debugfs_deinit(ser); 300 tty_kref_put(tty); 301 } 302 rtnl_unlock(); 303 } 304 } 305 306 static DECLARE_WORK(ser_release_work, ser_release); 307 308 static int ldisc_open(struct tty_struct *tty) 309 { 310 struct ser_device *ser; 311 struct net_device *dev; 312 char name[64]; 313 int result; 314 315 /* No write no play */ 316 if (tty->ops->write == NULL) 317 return -EOPNOTSUPP; 318 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_TTY_CONFIG)) 319 return -EPERM; 320 321 /* release devices to avoid name collision */ 322 ser_release(NULL); 323 324 result = snprintf(name, sizeof(name), "cf%s", tty->name); 325 if (result >= IFNAMSIZ) 326 return -EINVAL; 327 dev = alloc_netdev(sizeof(*ser), name, NET_NAME_UNKNOWN, 328 caifdev_setup); 329 if (!dev) 330 return -ENOMEM; 331 332 ser = netdev_priv(dev); 333 ser->tty = tty_kref_get(tty); 334 ser->dev = dev; 335 debugfs_init(ser, tty); 336 tty->receive_room = 4096; 337 tty->disc_data = ser; 338 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); 339 rtnl_lock(); 340 result = register_netdevice(dev); 341 if (result) { 342 tty_kref_put(tty); 343 rtnl_unlock(); 344 free_netdev(dev); 345 return -ENODEV; 346 } 347 348 spin_lock(&ser_lock); 349 list_add(&ser->node, &ser_list); 350 spin_unlock(&ser_lock); 351 rtnl_unlock(); 352 netif_stop_queue(dev); 353 update_tty_status(ser); 354 return 0; 355 } 356 357 static void ldisc_close(struct tty_struct *tty) 358 { 359 struct ser_device *ser = tty->disc_data; 360 361 spin_lock(&ser_lock); 362 list_move(&ser->node, &ser_release_list); 363 spin_unlock(&ser_lock); 364 schedule_work(&ser_release_work); 365 } 366 367 /* The line discipline structure. */ 368 static struct tty_ldisc_ops caif_ldisc = { 369 .owner = THIS_MODULE, 370 .num = N_CAIF, 371 .name = "n_caif", 372 .open = ldisc_open, 373 .close = ldisc_close, 374 .receive_buf = ldisc_receive, 375 .write_wakeup = ldisc_tx_wakeup 376 }; 377 378 static const struct net_device_ops netdev_ops = { 379 .ndo_open = caif_net_open, 380 .ndo_stop = caif_net_close, 381 .ndo_start_xmit = caif_xmit 382 }; 383 384 static void caifdev_setup(struct net_device *dev) 385 { 386 struct ser_device *serdev = netdev_priv(dev); 387 388 dev->features = 0; 389 dev->netdev_ops = &netdev_ops; 390 dev->type = ARPHRD_CAIF; 391 dev->flags = IFF_POINTOPOINT | IFF_NOARP; 392 dev->mtu = CAIF_MAX_MTU; 393 dev->priv_flags |= IFF_NO_QUEUE; 394 dev->needs_free_netdev = true; 395 skb_queue_head_init(&serdev->head); 396 serdev->common.link_select = CAIF_LINK_LOW_LATENCY; 397 serdev->common.use_frag = true; 398 serdev->common.use_stx = ser_use_stx; 399 serdev->common.use_fcs = ser_use_fcs; 400 serdev->dev = dev; 401 } 402 403 404 static int caif_net_open(struct net_device *dev) 405 { 406 netif_wake_queue(dev); 407 return 0; 408 } 409 410 static int caif_net_close(struct net_device *dev) 411 { 412 netif_stop_queue(dev); 413 return 0; 414 } 415 416 static int __init caif_ser_init(void) 417 { 418 int ret; 419 420 ret = tty_register_ldisc(&caif_ldisc); 421 if (ret < 0) 422 pr_err("cannot register CAIF ldisc=%d err=%d\n", N_CAIF, ret); 423 424 debugfsdir = debugfs_create_dir("caif_serial", NULL); 425 return ret; 426 } 427 428 static void __exit caif_ser_exit(void) 429 { 430 spin_lock(&ser_lock); 431 list_splice(&ser_list, &ser_release_list); 432 spin_unlock(&ser_lock); 433 ser_release(NULL); 434 cancel_work_sync(&ser_release_work); 435 tty_unregister_ldisc(&caif_ldisc); 436 debugfs_remove_recursive(debugfsdir); 437 } 438 439 module_init(caif_ser_init); 440 module_exit(caif_ser_exit); 441