Linux Audio

Check our new training course

Embedded Linux Audio

Check our new training course
with Creative Commons CC-BY-SA
lecture materials

Bootlin logo

Elixir Cross Referencer

Loading...
  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
/*********************************************************************
 *
 * Filename:      wrapper.c
 * Version:       1.2
 * Description:   IrDA SIR async wrapper layer
 * Status:        Stable
 * Author:        Dag Brattli <dagb@cs.uit.no>
 * Created at:    Mon Aug  4 20:40:53 1997
 * Modified at:   Fri Jan 28 13:21:09 2000
 * Modified by:   Dag Brattli <dagb@cs.uit.no>
 * Modified at:   Fri May 28  3:11 CST 1999
 * Modified by:   Horst von Brand <vonbrand@sleipnir.valparaiso.cl>
 *
 *     Copyright (c) 1998-2000 Dag Brattli <dagb@cs.uit.no>,
 *     All Rights Reserved.
 *     Copyright (c) 2000-2002 Jean Tourrilhes <jt@hpl.hp.com>
 *
 *     This program is free software; you can redistribute it and/or
 *     modify it under the terms of the GNU General Public License as
 *     published by the Free Software Foundation; either version 2 of
 *     the License, or (at your option) any later version.
 *
 *     Neither Dag Brattli nor University of Tromsø admit liability nor
 *     provide warranty for any of this software. This material is
 *     provided "AS-IS" and at no charge.
 *
 ********************************************************************/

#include <linux/skbuff.h>
#include <linux/string.h>
#include <linux/module.h>
#include <asm/byteorder.h>

#include <net/irda/irda.h>
#include <net/irda/wrapper.h>
#include <net/irda/crc.h>
#include <net/irda/irlap.h>
#include <net/irda/irlap_frame.h>
#include <net/irda/irda_device.h>

/************************** FRAME WRAPPING **************************/
/*
 * Unwrap and unstuff SIR frames
 *
 * Note : at FIR and MIR, HDLC framing is used and usually handled
 * by the controller, so we come here only for SIR... Jean II
 */

/*
 * Function stuff_byte (byte, buf)
 *
 *    Byte stuff one single byte and put the result in buffer pointed to by
 *    buf. The buffer must at all times be able to have two bytes inserted.
 *
 * This is in a tight loop, better inline it, so need to be prior to callers.
 * (2000 bytes on P6 200MHz, non-inlined ~370us, inline ~170us) - Jean II
 */
static inline int stuff_byte(__u8 byte, __u8 *buf)
{
	switch (byte) {
	case BOF: /* FALLTHROUGH */
	case EOF: /* FALLTHROUGH */
	case CE:
		/* Insert transparently coded */
		buf[0] = CE;               /* Send link escape */
		buf[1] = byte^IRDA_TRANS;    /* Complement bit 5 */
		return 2;
		/* break; */
	default:
		 /* Non-special value, no transparency required */
		buf[0] = byte;
		return 1;
		/* break; */
	}
}

/*
 * Function async_wrap (skb, *tx_buff, buffsize)
 *
 *    Makes a new buffer with wrapping and stuffing, should check that
 *    we don't get tx buffer overflow.
 */
int async_wrap_skb(struct sk_buff *skb, __u8 *tx_buff, int buffsize)
{
	struct irda_skb_cb *cb = (struct irda_skb_cb *) skb->cb;
	int xbofs;
	int i;
	int n;
	union {
		__u16 value;
		__u8 bytes[2];
	} fcs;

	/* Initialize variables */
	fcs.value = INIT_FCS;
	n = 0;

	/*
	 *  Send  XBOF's for required min. turn time and for the negotiated
	 *  additional XBOFS
	 */

	if (cb->magic != LAP_MAGIC) {
		/*
		 * This will happen for all frames sent from user-space.
		 * Nothing to worry about, but we set the default number of
		 * BOF's
		 */
		IRDA_DEBUG(1, "%s(), wrong magic in skb!\n", __func__);
		xbofs = 10;
	} else
		xbofs = cb->xbofs + cb->xbofs_delay;

	IRDA_DEBUG(4, "%s(), xbofs=%d\n", __func__, xbofs);

	/* Check that we never use more than 115 + 48 xbofs */
	if (xbofs > 163) {
		IRDA_DEBUG(0, "%s(), too many xbofs (%d)\n", __func__,
			   xbofs);
		xbofs = 163;
	}

	memset(tx_buff + n, XBOF, xbofs);
	n += xbofs;

	/* Start of packet character BOF */
	tx_buff[n++] = BOF;

	/* Insert frame and calc CRC */
	for (i=0; i < skb->len; i++) {
		/*
		 *  Check for the possibility of tx buffer overflow. We use
		 *  bufsize-5 since the maximum number of bytes that can be
		 *  transmitted after this point is 5.
		 */
		if(n >= (buffsize-5)) {
			IRDA_ERROR("%s(), tx buffer overflow (n=%d)\n",
				   __func__, n);
			return n;
		}

		n += stuff_byte(skb->data[i], tx_buff+n);
		fcs.value = irda_fcs(fcs.value, skb->data[i]);
	}

	/* Insert CRC in little endian format (LSB first) */
	fcs.value = ~fcs.value;
#ifdef __LITTLE_ENDIAN
	n += stuff_byte(fcs.bytes[0], tx_buff+n);
	n += stuff_byte(fcs.bytes[1], tx_buff+n);
#else /* ifdef __BIG_ENDIAN */
	n += stuff_byte(fcs.bytes[1], tx_buff+n);
	n += stuff_byte(fcs.bytes[0], tx_buff+n);
#endif
	tx_buff[n++] = EOF;

	return n;
}
EXPORT_SYMBOL(async_wrap_skb);

/************************* FRAME UNWRAPPING *************************/
/*
 * Unwrap and unstuff SIR frames
 *
 * Complete rewrite by Jean II :
 * More inline, faster, more compact, more logical. Jean II
 * (16 bytes on P6 200MHz, old 5 to 7 us, new 4 to 6 us)
 * (24 bytes on P6 200MHz, old 9 to 10 us, new 7 to 8 us)
 * (for reference, 115200 b/s is 1 byte every 69 us)
 * And reduce wrapper.o by ~900B in the process ;-)
 *
 * Then, we have the addition of ZeroCopy, which is optional
 * (i.e. the driver must initiate it) and improve final processing.
 * (2005 B frame + EOF on P6 200MHz, without 30 to 50 us, with 10 to 25 us)
 *
 * Note : at FIR and MIR, HDLC framing is used and usually handled
 * by the controller, so we come here only for SIR... Jean II
 */

/*
 * We can also choose where we want to do the CRC calculation. We can
 * do it "inline", as we receive the bytes, or "postponed", when
 * receiving the End-Of-Frame.
 * (16 bytes on P6 200MHz, inlined 4 to 6 us, postponed 4 to 5 us)
 * (24 bytes on P6 200MHz, inlined 7 to 8 us, postponed 5 to 7 us)
 * With ZeroCopy :
 * (2005 B frame on P6 200MHz, inlined 10 to 25 us, postponed 140 to 180 us)
 * Without ZeroCopy :
 * (2005 B frame on P6 200MHz, inlined 30 to 50 us, postponed 150 to 180 us)
 * (Note : numbers taken with irq disabled)
 *
 * From those numbers, it's not clear which is the best strategy, because
 * we end up running through a lot of data one way or another (i.e. cache
 * misses). I personally prefer to avoid the huge latency spike of the
 * "postponed" solution, because it come just at the time when we have
 * lot's of protocol processing to do and it will hurt our ability to
 * reach low link turnaround times... Jean II
 */
//#define POSTPONE_RX_CRC

/*
 * Function async_bump (buf, len, stats)
 *
 *    Got a frame, make a copy of it, and pass it up the stack! We can try
 *    to inline it since it's only called from state_inside_frame
 */
static inline void
async_bump(struct net_device *dev,
	   struct net_device_stats *stats,
	   iobuff_t *rx_buff)
{
	struct sk_buff *newskb;
	struct sk_buff *dataskb;
	int		docopy;

	/* Check if we need to copy the data to a new skb or not.
	 * If the driver doesn't use ZeroCopy Rx, we have to do it.
	 * With ZeroCopy Rx, the rx_buff already point to a valid
	 * skb. But, if the frame is small, it is more efficient to
	 * copy it to save memory (copy will be fast anyway - that's
	 * called Rx-copy-break). Jean II */
	docopy = ((rx_buff->skb == NULL) ||
		  (rx_buff->len < IRDA_RX_COPY_THRESHOLD));

	/* Allocate a new skb */
	newskb = dev_alloc_skb(docopy ? rx_buff->len + 1 : rx_buff->truesize);
	if (!newskb)  {
		stats->rx_dropped++;
		/* We could deliver the current skb if doing ZeroCopy Rx,
		 * but this would stall the Rx path. Better drop the
		 * packet... Jean II */
		return;
	}

	/* Align IP header to 20 bytes (i.e. increase skb->data)
	 * Note this is only useful with IrLAN, as PPP has a variable
	 * header size (2 or 1 bytes) - Jean II */
	skb_reserve(newskb, 1);

	if(docopy) {
		/* Copy data without CRC (length already checked) */
		skb_copy_to_linear_data(newskb, rx_buff->data,
					rx_buff->len - 2);
		/* Deliver this skb */
		dataskb = newskb;
	} else {
		/* We are using ZeroCopy. Deliver old skb */
		dataskb = rx_buff->skb;
		/* And hook the new skb to the rx_buff */
		rx_buff->skb = newskb;
		rx_buff->head = newskb->data;	/* NOT newskb->head */
		//printk(KERN_DEBUG "ZeroCopy : len = %d, dataskb = %p, newskb = %p\n", rx_buff->len, dataskb, newskb);
	}

	/* Set proper length on skb (without CRC) */
	skb_put(dataskb, rx_buff->len - 2);

	/* Feed it to IrLAP layer */
	dataskb->dev = dev;
	skb_reset_mac_header(dataskb);
	dataskb->protocol = htons(ETH_P_IRDA);

	netif_rx(dataskb);

	stats->rx_packets++;
	stats->rx_bytes += rx_buff->len;

	/* Clean up rx_buff (redundant with async_unwrap_bof() ???) */
	rx_buff->data = rx_buff->head;
	rx_buff->len = 0;
}

/*
 * Function async_unwrap_bof(dev, byte)
 *
 *    Handle Beginning Of Frame character received within a frame
 *
 */
static inline void
async_unwrap_bof(struct net_device *dev,
		 struct net_device_stats *stats,
		 iobuff_t *rx_buff, __u8 byte)
{
	switch(rx_buff->state) {
	case LINK_ESCAPE:
	case INSIDE_FRAME:
		/* Not supposed to happen, the previous frame is not
		 * finished - Jean II */
		IRDA_DEBUG(1, "%s(), Discarding incomplete frame\n",
			   __func__);
		stats->rx_errors++;
		stats->rx_missed_errors++;
		irda_device_set_media_busy(dev, TRUE);
		break;

	case OUTSIDE_FRAME:
	case BEGIN_FRAME:
	default:
		/* We may receive multiple BOF at the start of frame */
		break;
	}

	/* Now receiving frame */
	rx_buff->state = BEGIN_FRAME;
	rx_buff->in_frame = TRUE;

	/* Time to initialize receive buffer */
	rx_buff->data = rx_buff->head;
	rx_buff->len = 0;
	rx_buff->fcs = INIT_FCS;
}

/*
 * Function async_unwrap_eof(dev, byte)
 *
 *    Handle End Of Frame character received within a frame
 *
 */
static inline void
async_unwrap_eof(struct net_device *dev,
		 struct net_device_stats *stats,
		 iobuff_t *rx_buff, __u8 byte)
{
#ifdef POSTPONE_RX_CRC
	int	i;
#endif

	switch(rx_buff->state) {
	case OUTSIDE_FRAME:
		/* Probably missed the BOF */
		stats->rx_errors++;
		stats->rx_missed_errors++;
		irda_device_set_media_busy(dev, TRUE);
		break;

	case BEGIN_FRAME:
	case LINK_ESCAPE:
	case INSIDE_FRAME:
	default:
		/* Note : in the case of BEGIN_FRAME and LINK_ESCAPE,
		 * the fcs will most likely not match and generate an
		 * error, as expected - Jean II */
		rx_buff->state = OUTSIDE_FRAME;
		rx_buff->in_frame = FALSE;

#ifdef POSTPONE_RX_CRC
		/* If we haven't done the CRC as we receive bytes, we
		 * must do it now... Jean II */
		for(i = 0; i < rx_buff->len; i++)
			rx_buff->fcs = irda_fcs(rx_buff->fcs,
						rx_buff->data[i]);
#endif

		/* Test FCS and signal success if the frame is good */
		if (rx_buff->fcs == GOOD_FCS) {
			/* Deliver frame */
			async_bump(dev, stats, rx_buff);
			break;
		} else {
			/* Wrong CRC, discard frame!  */
			irda_device_set_media_busy(dev, TRUE);

			IRDA_DEBUG(1, "%s(), crc error\n", __func__);
			stats->rx_errors++;
			stats->rx_crc_errors++;
		}
		break;
	}
}

/*
 * Function async_unwrap_ce(dev, byte)
 *
 *    Handle Character Escape character received within a frame
 *
 */
static inline void
async_unwrap_ce(struct net_device *dev,
		 struct net_device_stats *stats,
		 iobuff_t *rx_buff, __u8 byte)
{
	switch(rx_buff->state) {
	case OUTSIDE_FRAME:
		/* Activate carrier sense */
		irda_device_set_media_busy(dev, TRUE);
		break;

	case LINK_ESCAPE:
		IRDA_WARNING("%s: state not defined\n", __func__);
		break;

	case BEGIN_FRAME:
	case INSIDE_FRAME:
	default:
		/* Stuffed byte coming */
		rx_buff->state = LINK_ESCAPE;
		break;
	}
}

/*
 * Function async_unwrap_other(dev, byte)
 *
 *    Handle other characters received within a frame
 *
 */
static inline void
async_unwrap_other(struct net_device *dev,
		   struct net_device_stats *stats,
		   iobuff_t *rx_buff, __u8 byte)
{
	switch(rx_buff->state) {
		/* This is on the critical path, case are ordered by
		 * probability (most frequent first) - Jean II */
	case INSIDE_FRAME:
		/* Must be the next byte of the frame */
		if (rx_buff->len < rx_buff->truesize)  {
			rx_buff->data[rx_buff->len++] = byte;
#ifndef POSTPONE_RX_CRC
			rx_buff->fcs = irda_fcs(rx_buff->fcs, byte);
#endif
		} else {
			IRDA_DEBUG(1, "%s(), Rx buffer overflow, aborting\n",
				   __func__);
			rx_buff->state = OUTSIDE_FRAME;
		}
		break;

	case LINK_ESCAPE:
		/*
		 *  Stuffed char, complement bit 5 of byte
		 *  following CE, IrLAP p.114
		 */
		byte ^= IRDA_TRANS;
		if (rx_buff->len < rx_buff->truesize)  {
			rx_buff->data[rx_buff->len++] = byte;
#ifndef POSTPONE_RX_CRC
			rx_buff->fcs = irda_fcs(rx_buff->fcs, byte);
#endif
			rx_buff->state = INSIDE_FRAME;
		} else {
			IRDA_DEBUG(1, "%s(), Rx buffer overflow, aborting\n",
				   __func__);
			rx_buff->state = OUTSIDE_FRAME;
		}
		break;

	case OUTSIDE_FRAME:
		/* Activate carrier sense */
		if(byte != XBOF)
			irda_device_set_media_busy(dev, TRUE);
		break;

	case BEGIN_FRAME:
	default:
		rx_buff->data[rx_buff->len++] = byte;
#ifndef POSTPONE_RX_CRC
		rx_buff->fcs = irda_fcs(rx_buff->fcs, byte);
#endif
		rx_buff->state = INSIDE_FRAME;
		break;
	}
}

/*
 * Function async_unwrap_char (dev, rx_buff, byte)
 *
 *    Parse and de-stuff frame received from the IrDA-port
 *
 * This is the main entry point for SIR drivers.
 */
void async_unwrap_char(struct net_device *dev,
		       struct net_device_stats *stats,
		       iobuff_t *rx_buff, __u8 byte)
{
	switch(byte) {
	case CE:
		async_unwrap_ce(dev, stats, rx_buff, byte);
		break;
	case BOF:
		async_unwrap_bof(dev, stats, rx_buff, byte);
		break;
	case EOF:
		async_unwrap_eof(dev, stats, rx_buff, byte);
		break;
	default:
		async_unwrap_other(dev, stats, rx_buff, byte);
		break;
	}
}
EXPORT_SYMBOL(async_unwrap_char);