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 = 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 = 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 u8 *flags, size_t count)
300 {
301 struct nci_uart *nu = 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 * cmd IOCTL command code
321 * arg argument for IOCTL call (cmd dependent)
322 *
323 * Return Value: Command dependent
324 */
325 static int nci_uart_tty_ioctl(struct tty_struct *tty, unsigned int cmd,
326 unsigned long arg)
327 {
328 struct nci_uart *nu = tty->disc_data;
329 int err = 0;
330
331 switch (cmd) {
332 case NCIUARTSETDRIVER:
333 if (!nu)
334 return nci_uart_set_driver(tty, (unsigned int)arg);
335 else
336 return -EBUSY;
337 break;
338 default:
339 err = n_tty_ioctl_helper(tty, cmd, arg);
340 break;
341 }
342
343 return err;
344 }
345
346 /* We don't provide read/write/poll interface for user space. */
347 static ssize_t nci_uart_tty_read(struct tty_struct *tty, struct file *file,
348 u8 *buf, size_t nr, void **cookie,
349 unsigned long offset)
350 {
351 return 0;
352 }
353
354 static ssize_t nci_uart_tty_write(struct tty_struct *tty, struct file *file,
355 const u8 *data, size_t count)
356 {
357 return 0;
358 }
359
360 static int nci_uart_send(struct nci_uart *nu, struct sk_buff *skb)
361 {
362 /* Queue TX packet */
363 skb_queue_tail(&nu->tx_q, skb);
364
365 /* Try to start TX (if possible) */
366 nci_uart_tx_wakeup(nu);
367
368 return 0;
369 }
370
371 int nci_uart_register(struct nci_uart *nu)
372 {
373 if (!nu || !nu->ops.open ||
374 !nu->ops.recv || !nu->ops.close)
375 return -EINVAL;
376
377 /* Set the send callback */
378 nu->ops.send = nci_uart_send;
379
380 /* Add this driver in the driver list */
381 if (nci_uart_drivers[nu->driver]) {
382 pr_err("driver %d is already registered\n", nu->driver);
383 return -EBUSY;
384 }
385 nci_uart_drivers[nu->driver] = nu;
386
387 pr_info("NCI uart driver '%s [%d]' registered\n", nu->name, nu->driver);
388
389 return 0;
390 }
391 EXPORT_SYMBOL_GPL(nci_uart_register);
392
393 void nci_uart_unregister(struct nci_uart *nu)
394 {
395 pr_info("NCI uart driver '%s [%d]' unregistered\n", nu->name,
396 nu->driver);
397
398 /* Remove this driver from the driver list */
399 nci_uart_drivers[nu->driver] = NULL;
400 }
401 EXPORT_SYMBOL_GPL(nci_uart_unregister);
402
403 void nci_uart_set_config(struct nci_uart *nu, int baudrate, int flow_ctrl)
404 {
405 struct ktermios new_termios;
406
407 if (!nu->tty)
408 return;
409
410 down_read(&nu->tty->termios_rwsem);
411 new_termios = nu->tty->termios;
412 up_read(&nu->tty->termios_rwsem);
413 tty_termios_encode_baud_rate(&new_termios, baudrate, baudrate);
414
415 if (flow_ctrl)
416 new_termios.c_cflag |= CRTSCTS;
417 else
418 new_termios.c_cflag &= ~CRTSCTS;
419
420 tty_set_termios(nu->tty, &new_termios);
421 }
422 EXPORT_SYMBOL_GPL(nci_uart_set_config);
423
424 static struct tty_ldisc_ops nci_uart_ldisc = {
425 .owner = THIS_MODULE,
426 .num = N_NCI,
427 .name = "n_nci",
428 .open = nci_uart_tty_open,
429 .close = nci_uart_tty_close,
430 .read = nci_uart_tty_read,
431 .write = nci_uart_tty_write,
432 .receive_buf = nci_uart_tty_receive,
433 .write_wakeup = nci_uart_tty_wakeup,
434 .ioctl = nci_uart_tty_ioctl,
435 .compat_ioctl = nci_uart_tty_ioctl,
436 };
437
438 static int __init nci_uart_init(void)
439 {
440 return tty_register_ldisc(&nci_uart_ldisc);
441 }
442
443 static void __exit nci_uart_exit(void)
444 {
445 tty_unregister_ldisc(&nci_uart_ldisc);
446 }
447
448 module_init(nci_uart_init);
449 module_exit(nci_uart_exit);
450
451 MODULE_AUTHOR("Marvell International Ltd.");
452 MODULE_DESCRIPTION("NFC NCI UART driver");
453 MODULE_LICENSE("GPL");
454 MODULE_ALIAS_LDISC(N_NCI);
455
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