summaryrefslogtreecommitdiffstats
path: root/net/nfc/nci/uart.c
blob: 21d8875673a42229f233ca20af640c53e325a4bb (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
/*
 * Copyright (C) 2015, Marvell International Ltd.
 *
 * This software file (the "File") is distributed by Marvell International
 * Ltd. under the terms of the GNU General Public License Version 2, June 1991
 * (the "License").  You may use, redistribute and/or modify this File in
 * accordance with the terms and conditions of the License, a copy of which
 * is available on the worldwide web at
 * http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt.
 *
 * THE FILE IS DISTRIBUTED AS-IS, WITHOUT WARRANTY OF ANY KIND, AND THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE
 * ARE EXPRESSLY DISCLAIMED.  The License provides additional details about
 * this warranty disclaimer.
 */

/* Inspired (hugely) by HCI LDISC implementation in Bluetooth.
 *
 *  Copyright (C) 2000-2001  Qualcomm Incorporated
 *  Copyright (C) 2002-2003  Maxim Krasnyansky <maxk@qualcomm.com>
 *  Copyright (C) 2004-2005  Marcel Holtmann <marcel@holtmann.org>
 */

#include <linux/module.h>

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/fcntl.h>
#include <linux/interrupt.h>
#include <linux/ptrace.h>
#include <linux/poll.h>

#include <linux/slab.h>
#include <linux/tty.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/signal.h>
#include <linux/ioctl.h>
#include <linux/skbuff.h>

#include <net/nfc/nci.h>
#include <net/nfc/nci_core.h>

/* TX states  */
#define NCI_UART_SENDING	1
#define NCI_UART_TX_WAKEUP	2

static struct nci_uart *nci_uart_drivers[NCI_UART_DRIVER_MAX];

static inline struct sk_buff *nci_uart_dequeue(struct nci_uart *nu)
{
	struct sk_buff *skb = nu->tx_skb;

	if (!skb)
		skb = skb_dequeue(&nu->tx_q);
	else
		nu->tx_skb = NULL;

	return skb;
}

static inline int nci_uart_queue_empty(struct nci_uart *nu)
{
	if (nu->tx_skb)
		return 0;

	return skb_queue_empty(&nu->tx_q);
}

static int nci_uart_tx_wakeup(struct nci_uart *nu)
{
	if (test_and_set_bit(NCI_UART_SENDING, &nu->tx_state)) {
		set_bit(NCI_UART_TX_WAKEUP, &nu->tx_state);
		return 0;
	}

	schedule_work(&nu->write_work);

	return 0;
}

static void nci_uart_write_work(struct work_struct *work)
{
	struct nci_uart *nu = container_of(work, struct nci_uart, write_work);
	struct tty_struct *tty = nu->tty;
	struct sk_buff *skb;

restart:
	clear_bit(NCI_UART_TX_WAKEUP, &nu->tx_state);

	if (nu->ops.tx_start)
		nu->ops.tx_start(nu);

	while ((skb = nci_uart_dequeue(nu))) {
		int len;

		set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
		len = tty->ops->write(tty, skb->data, skb->len);
		skb_pull(skb, len);
		if (skb->len) {
			nu->tx_skb = skb;
			break;
		}
		kfree_skb(skb);
	}

	if (test_bit(NCI_UART_TX_WAKEUP, &nu->tx_state))
		goto restart;

	if (nu->ops.tx_done && nci_uart_queue_empty(nu))
		nu->ops.tx_done(nu);

	clear_bit(NCI_UART_SENDING, &nu->tx_state);
}

static int nci_uart_set_driver(struct tty_struct *tty, unsigned int driver)
{
	struct nci_uart *nu = NULL;
	int ret;

	if (driver >= NCI_UART_DRIVER_MAX)
		return -EINVAL;

	if (!nci_uart_drivers[driver])
		return -ENOENT;

	nu = kzalloc(sizeof(*nu), GFP_KERNEL);
	if (!nu)
		return -ENOMEM;

	memcpy(nu, nci_uart_drivers[driver], sizeof(struct nci_uart));
	nu->tty = tty;
	tty->disc_data = nu;
	skb_queue_head_init(&nu->tx_q);
	INIT_WORK(&nu->write_work, nci_uart_write_work);
	spin_lock_init(&nu->rx_lock);

	ret = nu->ops.open(nu);
	if (ret) {
		tty->disc_data = NULL;
		kfree(nu);
	} else if (!try_module_get(nu->owner)) {
		nu->ops.close(nu);
		tty->disc_data = NULL;
		kfree(nu);
		return -ENOENT;
	}
	return ret;
}

/* ------ LDISC part ------ */

/* nci_uart_tty_open
 *
 *     Called when line discipline changed to NCI_UART.
 *
 * Arguments:
 *     tty    pointer to tty info structure
 * Return Value:
 *     0 if success, otherwise error code
 */
static int nci_uart_tty_open(struct tty_struct *tty)
{
	/* Error if the tty has no write op instead of leaving an exploitable
	 * hole
	 */
	if (!tty->ops->write)
		return -EOPNOTSUPP;

	tty->disc_data = NULL;
	tty->receive_room = 65536;

	/* Flush any pending characters in the driver and line discipline. */

	/* FIXME: why is this needed. Note don't use ldisc_ref here as the
	 * open path is before the ldisc is referencable.
	 */

	if (tty->ldisc->ops->flush_buffer)
		tty->ldisc->ops->flush_buffer(tty);
	tty_driver_flush_buffer(tty);

	return 0;
}

/* nci_uart_tty_close()
 *
 *    Called when the line discipline is changed to something
 *    else, the tty is closed, or the tty detects a hangup.
 */
static void nci_uart_tty_close(struct tty_struct *tty)
{
	struct nci_uart *nu = (void *)tty->disc_data;

	/* Detach from the tty */
	tty->disc_data = NULL;

	if (!nu)
		return;

	if (nu->tx_skb)
		kfree_skb(nu->tx_skb);
	if (nu->rx_skb)
		kfree_skb(nu->rx_skb);

	skb_queue_purge(&nu->tx_q);

	nu->ops.close(nu);
	nu->tty = NULL;
	module_put(nu->owner);

	cancel_work_sync(&nu->write_work);

	kfree(nu);
}

/* nci_uart_tty_wakeup()
 *
 *    Callback for transmit wakeup. Called when low level
 *    device driver can accept more send data.
 *
 * Arguments:        tty    pointer to associated tty instance data
 * Return Value:    None
 */
static void nci_uart_tty_wakeup(struct tty_struct *tty)
{
	struct nci_uart *nu = (void *)tty->disc_data;

	if (!nu)
		return;

	clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);

	if (tty != nu->tty)
		return;

	nci_uart_tx_wakeup(nu);
}

/* nci_uart_tty_receive()
 *
 *     Called by tty low level driver when receive data is
 *     available.
 *
 * Arguments:  tty          pointer to tty isntance data
 *             data         pointer to received data
 *             flags        pointer to flags for data
 *             count        count of received data in bytes
 *
 * Return Value:    None
 */
static void nci_uart_tty_receive(struct tty_struct *tty, const u8 *data,
				 char *flags, int count)
{
	struct nci_uart *nu = (void *)tty->disc_data;

	if (!nu || tty != nu->tty)
		return;

	spin_lock(&nu->rx_lock);
	nu->ops.recv_buf(nu, (void *)data, flags, count);
	spin_unlock(&nu->rx_lock);

	tty_unthrottle(tty);
}

/* nci_uart_tty_ioctl()
 *
 *    Process IOCTL system call for the tty device.
 *
 * Arguments:
 *
 *    tty        pointer to tty instance data
 *    file       pointer to open file object for device
 *    cmd        IOCTL command code
 *    arg        argument for IOCTL call (cmd dependent)
 *
 * Return Value:    Command dependent
 */
static int nci_uart_tty_ioctl(struct tty_struct *tty, struct file *file,
			      unsigned int cmd, unsigned long arg)
{
	struct nci_uart *nu = (void *)tty->disc_data;
	int err = 0;

	switch (cmd) {
	case NCIUARTSETDRIVER:
		if (!nu)
			return nci_uart_set_driver(tty, (unsigned int)arg);
		else
			return -EBUSY;
		break;
	default:
		err = n_tty_ioctl_helper(tty, file, cmd, arg);
		break;
	}

	return err;
}

/* We don't provide read/write/poll interface for user space. */
static ssize_t nci_uart_tty_read(struct tty_struct *tty, struct file *file,
				 unsigned char __user *buf, size_t nr)
{
	return 0;
}

static ssize_t nci_uart_tty_write(struct tty_struct *tty, struct file *file,
				  const unsigned char *data, size_t count)
{
	return 0;
}

static unsigned int nci_uart_tty_poll(struct tty_struct *tty,
				      struct file *filp, poll_table *wait)
{
	return 0;
}

static int nci_uart_send(struct nci_uart *nu, struct sk_buff *skb)
{
	/* Queue TX packet */
	skb_queue_tail(&nu->tx_q, skb);

	/* Try to start TX (if possible) */
	nci_uart_tx_wakeup(nu);

	return 0;
}

/* -- Default recv_buf handler --
 *
 * This handler supposes that NCI frames are sent over UART link without any
 * framing. It reads NCI header, retrieve the packet size and once all packet
 * bytes are received it passes it to nci_uart driver for processing.
 */
static int nci_uart_default_recv_buf(struct nci_uart *nu, const u8 *data,
				     char *flags, int count)
{
	int chunk_len;

	if (!nu->ndev) {
		nfc_err(nu->tty->dev,
			"receive data from tty but no NCI dev is attached yet, drop buffer\n");
		return 0;
	}

	/* Decode all incoming data in packets
	 * and enqueue then for processing.
	 */
	while (count > 0) {
		/* If this is the first data of a packet, allocate a buffer */
		if (!nu->rx_skb) {
			nu->rx_packet_len = -1;
			nu->rx_skb = nci_skb_alloc(nu->ndev,
						   NCI_MAX_PACKET_SIZE,
						   GFP_KERNEL);
			if (!nu->rx_skb)
				return -ENOMEM;
		}

		/* Eat byte after byte till full packet header is received */
		if (nu->rx_skb->len < NCI_CTRL_HDR_SIZE) {
			*skb_put(nu->rx_skb, 1) = *data++;
			--count;
			continue;
		}

		/* Header was received but packet len was not read */
		if (nu->rx_packet_len < 0)
			nu->rx_packet_len = NCI_CTRL_HDR_SIZE +
				nci_plen(nu->rx_skb->data);

		/* Compute how many bytes are missing and how many bytes can
		 * be consumed.
		 */
		chunk_len = nu->rx_packet_len - nu->rx_skb->len;
		if (count < chunk_len)
			chunk_len = count;
		memcpy(skb_put(nu->rx_skb, chunk_len), data, chunk_len);
		data += chunk_len;
		count -= chunk_len;

		/* Chcek if packet is fully received */
		if (nu->rx_packet_len == nu->rx_skb->len) {
			/* Pass RX packet to driver */
			if (nu->ops.recv(nu, nu->rx_skb) != 0)
				nfc_err(nu->tty->dev, "corrupted RX packet\n");
			/* Next packet will be a new one */
			nu->rx_skb = NULL;
		}
	}

	return 0;
}

/* -- Default recv handler -- */
static int nci_uart_default_recv(struct nci_uart *nu, struct sk_buff *skb)
{
	return nci_recv_frame(nu->ndev, skb);
}

int nci_uart_register(struct nci_uart *nu)
{
	if (!nu || !nu->ops.open ||
	    !nu->ops.recv || !nu->ops.close)
		return -EINVAL;

	/* Set the send callback */
	nu->ops.send = nci_uart_send;

	/* Install default handlers if not overridden */
	if (!nu->ops.recv_buf)
		nu->ops.recv_buf = nci_uart_default_recv_buf;
	if (!nu->ops.recv)
		nu->ops.recv = nci_uart_default_recv;

	/* Add this driver in the driver list */
	if (nci_uart_drivers[nu->driver]) {
		pr_err("driver %d is already registered\n", nu->driver);
		return -EBUSY;
	}
	nci_uart_drivers[nu->driver] = nu;

	pr_info("NCI uart driver '%s [%d]' registered\n", nu->name, nu->driver);

	return 0;
}
EXPORT_SYMBOL_GPL(nci_uart_register);

void nci_uart_unregister(struct nci_uart *nu)
{
	pr_info("NCI uart driver '%s [%d]' unregistered\n", nu->name,
		nu->driver);

	/* Remove this driver from the driver list */
	nci_uart_drivers[nu->driver] = NULL;
}
EXPORT_SYMBOL_GPL(nci_uart_unregister);

void nci_uart_set_config(struct nci_uart *nu, int baudrate, int flow_ctrl)
{
	struct ktermios new_termios;

	if (!nu->tty)
		return;

	down_read(&nu->tty->termios_rwsem);
	new_termios = nu->tty->termios;
	up_read(&nu->tty->termios_rwsem);
	tty_termios_encode_baud_rate(&new_termios, baudrate, baudrate);

	if (flow_ctrl)
		new_termios.c_cflag |= CRTSCTS;
	else
		new_termios.c_cflag &= ~CRTSCTS;

	tty_set_termios(nu->tty, &new_termios);
}
EXPORT_SYMBOL_GPL(nci_uart_set_config);

static struct tty_ldisc_ops nci_uart_ldisc = {
	.magic		= TTY_LDISC_MAGIC,
	.owner		= THIS_MODULE,
	.name		= "n_nci",
	.open		= nci_uart_tty_open,
	.close		= nci_uart_tty_close,
	.read		= nci_uart_tty_read,
	.write		= nci_uart_tty_write,
	.poll		= nci_uart_tty_poll,
	.receive_buf	= nci_uart_tty_receive,
	.write_wakeup	= nci_uart_tty_wakeup,
	.ioctl		= nci_uart_tty_ioctl,
};

static int __init nci_uart_init(void)
{
	memset(nci_uart_drivers, 0, sizeof(nci_uart_drivers));
	return tty_register_ldisc(N_NCI, &nci_uart_ldisc);
}

static void __exit nci_uart_exit(void)
{
	tty_unregister_ldisc(N_NCI);
}

module_init(nci_uart_init);
module_exit(nci_uart_exit);

MODULE_AUTHOR("Marvell International Ltd.");
MODULE_DESCRIPTION("NFC NCI UART driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_LDISC(N_NCI);