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1/*
2 * Copyright (C) 2015, Marvell International Ltd.
3 *
4 * This software file (the "File") is distributed by Marvell International
5 * Ltd. under the terms of the GNU General Public License Version 2, June 1991
6 * (the "License"). You may use, redistribute and/or modify this File in
7 * accordance with the terms and conditions of the License, a copy of which
8 * is available on the worldwide web at
9 * http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt.
10 *
11 * THE FILE IS DISTRIBUTED AS-IS, WITHOUT WARRANTY OF ANY KIND, AND THE
12 * IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE
13 * ARE EXPRESSLY DISCLAIMED. The License provides additional details about
14 * this warranty disclaimer.
15 */
16
17/* Inspired (hugely) by HCI LDISC implementation in Bluetooth.
18 *
19 * Copyright (C) 2000-2001 Qualcomm Incorporated
20 * Copyright (C) 2002-2003 Maxim Krasnyansky <maxk@qualcomm.com>
21 * Copyright (C) 2004-2005 Marcel Holtmann <marcel@holtmann.org>
22 */
23
24#include <linux/module.h>
25
26#include <linux/kernel.h>
27#include <linux/init.h>
28#include <linux/types.h>
29#include <linux/fcntl.h>
30#include <linux/interrupt.h>
31#include <linux/ptrace.h>
32#include <linux/poll.h>
33
34#include <linux/slab.h>
35#include <linux/tty.h>
36#include <linux/errno.h>
37#include <linux/string.h>
38#include <linux/signal.h>
39#include <linux/ioctl.h>
40#include <linux/skbuff.h>
41
42#include <net/nfc/nci.h>
43#include <net/nfc/nci_core.h>
44
45/* TX states */
46#define NCI_UART_SENDING 1
47#define NCI_UART_TX_WAKEUP 2
48
49static struct nci_uart *nci_uart_drivers[NCI_UART_DRIVER_MAX];
50
51static inline struct sk_buff *nci_uart_dequeue(struct nci_uart *nu)
52{
53 struct sk_buff *skb = nu->tx_skb;
54
55 if (!skb)
56 skb = skb_dequeue(&nu->tx_q);
57 else
58 nu->tx_skb = NULL;
59
60 return skb;
61}
62
63static inline int nci_uart_queue_empty(struct nci_uart *nu)
64{
65 if (nu->tx_skb)
66 return 0;
67
68 return skb_queue_empty(&nu->tx_q);
69}
70
71static int nci_uart_tx_wakeup(struct nci_uart *nu)
72{
73 if (test_and_set_bit(NCI_UART_SENDING, &nu->tx_state)) {
74 set_bit(NCI_UART_TX_WAKEUP, &nu->tx_state);
75 return 0;
76 }
77
78 schedule_work(&nu->write_work);
79
80 return 0;
81}
82
83static void nci_uart_write_work(struct work_struct *work)
84{
85 struct nci_uart *nu = container_of(work, struct nci_uart, write_work);
86 struct tty_struct *tty = nu->tty;
87 struct sk_buff *skb;
88
89restart:
90 clear_bit(NCI_UART_TX_WAKEUP, &nu->tx_state);
91
92 if (nu->ops.tx_start)
93 nu->ops.tx_start(nu);
94
95 while ((skb = nci_uart_dequeue(nu))) {
96 int len;
97
98 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
99 len = tty->ops->write(tty, skb->data, skb->len);
100 skb_pull(skb, len);
101 if (skb->len) {
102 nu->tx_skb = skb;
103 break;
104 }
105 kfree_skb(skb);
106 }
107
108 if (test_bit(NCI_UART_TX_WAKEUP, &nu->tx_state))
109 goto restart;
110
111 if (nu->ops.tx_done && nci_uart_queue_empty(nu))
112 nu->ops.tx_done(nu);
113
114 clear_bit(NCI_UART_SENDING, &nu->tx_state);
115}
116
117static int nci_uart_set_driver(struct tty_struct *tty, unsigned int driver)
118{
119 struct nci_uart *nu = NULL;
120 int ret;
121
122 if (driver >= NCI_UART_DRIVER_MAX)
123 return -EINVAL;
124
125 if (!nci_uart_drivers[driver])
126 return -ENOENT;
127
128 nu = kzalloc(sizeof(*nu), GFP_KERNEL);
129 if (!nu)
130 return -ENOMEM;
131
132 memcpy(nu, nci_uart_drivers[driver], sizeof(struct nci_uart));
133 nu->tty = tty;
134 tty->disc_data = nu;
135 skb_queue_head_init(&nu->tx_q);
136 INIT_WORK(&nu->write_work, nci_uart_write_work);
137 spin_lock_init(&nu->rx_lock);
138
139 ret = nu->ops.open(nu);
140 if (ret) {
141 tty->disc_data = NULL;
142 kfree(nu);
143 } else if (!try_module_get(nu->owner)) {
144 nu->ops.close(nu);
145 tty->disc_data = NULL;
146 kfree(nu);
147 return -ENOENT;
148 }
149 return ret;
150}
151
152/* ------ LDISC part ------ */
153
154/* nci_uart_tty_open
155 *
156 * Called when line discipline changed to NCI_UART.
157 *
158 * Arguments:
159 * tty pointer to tty info structure
160 * Return Value:
161 * 0 if success, otherwise error code
162 */
163static int nci_uart_tty_open(struct tty_struct *tty)
164{
165 /* Error if the tty has no write op instead of leaving an exploitable
166 * hole
167 */
168 if (!tty->ops->write)
169 return -EOPNOTSUPP;
170
171 tty->disc_data = NULL;
172 tty->receive_room = 65536;
173
174 /* Flush any pending characters in the driver */
175 tty_driver_flush_buffer(tty);
176
177 return 0;
178}
179
180/* nci_uart_tty_close()
181 *
182 * Called when the line discipline is changed to something
183 * else, the tty is closed, or the tty detects a hangup.
184 */
185static void nci_uart_tty_close(struct tty_struct *tty)
186{
187 struct nci_uart *nu = (void *)tty->disc_data;
188
189 /* Detach from the tty */
190 tty->disc_data = NULL;
191
192 if (!nu)
193 return;
194
195 kfree_skb(nu->tx_skb);
196 kfree_skb(nu->rx_skb);
197
198 skb_queue_purge(&nu->tx_q);
199
200 nu->ops.close(nu);
201 nu->tty = NULL;
202 module_put(nu->owner);
203
204 cancel_work_sync(&nu->write_work);
205
206 kfree(nu);
207}
208
209/* nci_uart_tty_wakeup()
210 *
211 * Callback for transmit wakeup. Called when low level
212 * device driver can accept more send data.
213 *
214 * Arguments: tty pointer to associated tty instance data
215 * Return Value: None
216 */
217static void nci_uart_tty_wakeup(struct tty_struct *tty)
218{
219 struct nci_uart *nu = (void *)tty->disc_data;
220
221 if (!nu)
222 return;
223
224 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
225
226 if (tty != nu->tty)
227 return;
228
229 nci_uart_tx_wakeup(nu);
230}
231
232/* -- Default recv_buf handler --
233 *
234 * This handler supposes that NCI frames are sent over UART link without any
235 * framing. It reads NCI header, retrieve the packet size and once all packet
236 * bytes are received it passes it to nci_uart driver for processing.
237 */
238static int nci_uart_default_recv_buf(struct nci_uart *nu, const u8 *data,
239 int count)
240{
241 int chunk_len;
242
243 if (!nu->ndev) {
244 nfc_err(nu->tty->dev,
245 "receive data from tty but no NCI dev is attached yet, drop buffer\n");
246 return 0;
247 }
248
249 /* Decode all incoming data in packets
250 * and enqueue then for processing.
251 */
252 while (count > 0) {
253 /* If this is the first data of a packet, allocate a buffer */
254 if (!nu->rx_skb) {
255 nu->rx_packet_len = -1;
256 nu->rx_skb = nci_skb_alloc(nu->ndev,
257 NCI_MAX_PACKET_SIZE,
258 GFP_ATOMIC);
259 if (!nu->rx_skb)
260 return -ENOMEM;
261 }
262
263 /* Eat byte after byte till full packet header is received */
264 if (nu->rx_skb->len < NCI_CTRL_HDR_SIZE) {
265 skb_put_u8(nu->rx_skb, *data++);
266 --count;
267 continue;
268 }
269
270 /* Header was received but packet len was not read */
271 if (nu->rx_packet_len < 0)
272 nu->rx_packet_len = NCI_CTRL_HDR_SIZE +
273 nci_plen(nu->rx_skb->data);
274
275 /* Compute how many bytes are missing and how many bytes can
276 * be consumed.
277 */
278 chunk_len = nu->rx_packet_len - nu->rx_skb->len;
279 if (count < chunk_len)
280 chunk_len = count;
281 skb_put_data(nu->rx_skb, data, chunk_len);
282 data += chunk_len;
283 count -= chunk_len;
284
285 /* Check if packet is fully received */
286 if (nu->rx_packet_len == nu->rx_skb->len) {
287 /* Pass RX packet to driver */
288 if (nu->ops.recv(nu, nu->rx_skb) != 0)
289 nfc_err(nu->tty->dev, "corrupted RX packet\n");
290 /* Next packet will be a new one */
291 nu->rx_skb = NULL;
292 }
293 }
294
295 return 0;
296}
297
298/* nci_uart_tty_receive()
299 *
300 * Called by tty low level driver when receive data is
301 * available.
302 *
303 * Arguments: tty pointer to tty instance data
304 * data pointer to received data
305 * flags pointer to flags for data
306 * count count of received data in bytes
307 *
308 * Return Value: None
309 */
310static void nci_uart_tty_receive(struct tty_struct *tty, const u8 *data,
311 const char *flags, int count)
312{
313 struct nci_uart *nu = (void *)tty->disc_data;
314
315 if (!nu || tty != nu->tty)
316 return;
317
318 spin_lock(&nu->rx_lock);
319 nci_uart_default_recv_buf(nu, data, count);
320 spin_unlock(&nu->rx_lock);
321
322 tty_unthrottle(tty);
323}
324
325/* nci_uart_tty_ioctl()
326 *
327 * Process IOCTL system call for the tty device.
328 *
329 * Arguments:
330 *
331 * tty pointer to tty instance data
332 * file pointer to open file object for device
333 * cmd IOCTL command code
334 * arg argument for IOCTL call (cmd dependent)
335 *
336 * Return Value: Command dependent
337 */
338static int nci_uart_tty_ioctl(struct tty_struct *tty, struct file *file,
339 unsigned int cmd, unsigned long arg)
340{
341 struct nci_uart *nu = (void *)tty->disc_data;
342 int err = 0;
343
344 switch (cmd) {
345 case NCIUARTSETDRIVER:
346 if (!nu)
347 return nci_uart_set_driver(tty, (unsigned int)arg);
348 else
349 return -EBUSY;
350 break;
351 default:
352 err = n_tty_ioctl_helper(tty, file, cmd, arg);
353 break;
354 }
355
356 return err;
357}
358
359/* We don't provide read/write/poll interface for user space. */
360static ssize_t nci_uart_tty_read(struct tty_struct *tty, struct file *file,
361 unsigned char *buf, size_t nr,
362 void **cookie, unsigned long offset)
363{
364 return 0;
365}
366
367static ssize_t nci_uart_tty_write(struct tty_struct *tty, struct file *file,
368 const unsigned char *data, size_t count)
369{
370 return 0;
371}
372
373static __poll_t nci_uart_tty_poll(struct tty_struct *tty,
374 struct file *filp, poll_table *wait)
375{
376 return 0;
377}
378
379static int nci_uart_send(struct nci_uart *nu, struct sk_buff *skb)
380{
381 /* Queue TX packet */
382 skb_queue_tail(&nu->tx_q, skb);
383
384 /* Try to start TX (if possible) */
385 nci_uart_tx_wakeup(nu);
386
387 return 0;
388}
389
390int nci_uart_register(struct nci_uart *nu)
391{
392 if (!nu || !nu->ops.open ||
393 !nu->ops.recv || !nu->ops.close)
394 return -EINVAL;
395
396 /* Set the send callback */
397 nu->ops.send = nci_uart_send;
398
399 /* Add this driver in the driver list */
400 if (nci_uart_drivers[nu->driver]) {
401 pr_err("driver %d is already registered\n", nu->driver);
402 return -EBUSY;
403 }
404 nci_uart_drivers[nu->driver] = nu;
405
406 pr_info("NCI uart driver '%s [%d]' registered\n", nu->name, nu->driver);
407
408 return 0;
409}
410EXPORT_SYMBOL_GPL(nci_uart_register);
411
412void nci_uart_unregister(struct nci_uart *nu)
413{
414 pr_info("NCI uart driver '%s [%d]' unregistered\n", nu->name,
415 nu->driver);
416
417 /* Remove this driver from the driver list */
418 nci_uart_drivers[nu->driver] = NULL;
419}
420EXPORT_SYMBOL_GPL(nci_uart_unregister);
421
422void nci_uart_set_config(struct nci_uart *nu, int baudrate, int flow_ctrl)
423{
424 struct ktermios new_termios;
425
426 if (!nu->tty)
427 return;
428
429 down_read(&nu->tty->termios_rwsem);
430 new_termios = nu->tty->termios;
431 up_read(&nu->tty->termios_rwsem);
432 tty_termios_encode_baud_rate(&new_termios, baudrate, baudrate);
433
434 if (flow_ctrl)
435 new_termios.c_cflag |= CRTSCTS;
436 else
437 new_termios.c_cflag &= ~CRTSCTS;
438
439 tty_set_termios(nu->tty, &new_termios);
440}
441EXPORT_SYMBOL_GPL(nci_uart_set_config);
442
443static struct tty_ldisc_ops nci_uart_ldisc = {
444 .owner = THIS_MODULE,
445 .num = N_NCI,
446 .name = "n_nci",
447 .open = nci_uart_tty_open,
448 .close = nci_uart_tty_close,
449 .read = nci_uart_tty_read,
450 .write = nci_uart_tty_write,
451 .poll = nci_uart_tty_poll,
452 .receive_buf = nci_uart_tty_receive,
453 .write_wakeup = nci_uart_tty_wakeup,
454 .ioctl = nci_uart_tty_ioctl,
455 .compat_ioctl = nci_uart_tty_ioctl,
456};
457
458static int __init nci_uart_init(void)
459{
460 return tty_register_ldisc(&nci_uart_ldisc);
461}
462
463static void __exit nci_uart_exit(void)
464{
465 tty_unregister_ldisc(&nci_uart_ldisc);
466}
467
468module_init(nci_uart_init);
469module_exit(nci_uart_exit);
470
471MODULE_AUTHOR("Marvell International Ltd.");
472MODULE_DESCRIPTION("NFC NCI UART driver");
473MODULE_LICENSE("GPL");
474MODULE_ALIAS_LDISC(N_NCI);