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path: root/drivers/isdn/i4l/isdnhdlc.c
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-rw-r--r--drivers/isdn/i4l/isdnhdlc.c630
1 files changed, 630 insertions, 0 deletions
diff --git a/drivers/isdn/i4l/isdnhdlc.c b/drivers/isdn/i4l/isdnhdlc.c
new file mode 100644
index 000000000..027d1c590
--- /dev/null
+++ b/drivers/isdn/i4l/isdnhdlc.c
@@ -0,0 +1,630 @@
+/*
+ * isdnhdlc.c -- General purpose ISDN HDLC decoder.
+ *
+ * Copyright (C)
+ * 2009 Karsten Keil <keil@b1-systems.de>
+ * 2002 Wolfgang Mües <wolfgang@iksw-muees.de>
+ * 2001 Frode Isaksen <fisaksen@bewan.com>
+ * 2001 Kai Germaschewski <kai.germaschewski@gmx.de>
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/crc-ccitt.h>
+#include <linux/isdn/hdlc.h>
+#include <linux/bitrev.h>
+
+/*-------------------------------------------------------------------*/
+
+MODULE_AUTHOR("Wolfgang Mües <wolfgang@iksw-muees.de>, "
+ "Frode Isaksen <fisaksen@bewan.com>, "
+ "Kai Germaschewski <kai.germaschewski@gmx.de>");
+MODULE_DESCRIPTION("General purpose ISDN HDLC decoder");
+MODULE_LICENSE("GPL");
+
+/*-------------------------------------------------------------------*/
+
+enum {
+ HDLC_FAST_IDLE, HDLC_GET_FLAG_B0, HDLC_GETFLAG_B1A6, HDLC_GETFLAG_B7,
+ HDLC_GET_DATA, HDLC_FAST_FLAG
+};
+
+enum {
+ HDLC_SEND_DATA, HDLC_SEND_CRC1, HDLC_SEND_FAST_FLAG,
+ HDLC_SEND_FIRST_FLAG, HDLC_SEND_CRC2, HDLC_SEND_CLOSING_FLAG,
+ HDLC_SEND_IDLE1, HDLC_SEND_FAST_IDLE, HDLC_SENDFLAG_B0,
+ HDLC_SENDFLAG_B1A6, HDLC_SENDFLAG_B7, STOPPED, HDLC_SENDFLAG_ONE
+};
+
+void isdnhdlc_rcv_init(struct isdnhdlc_vars *hdlc, u32 features)
+{
+ memset(hdlc, 0, sizeof(struct isdnhdlc_vars));
+ hdlc->state = HDLC_GET_DATA;
+ if (features & HDLC_56KBIT)
+ hdlc->do_adapt56 = 1;
+ if (features & HDLC_BITREVERSE)
+ hdlc->do_bitreverse = 1;
+}
+EXPORT_SYMBOL(isdnhdlc_out_init);
+
+void isdnhdlc_out_init(struct isdnhdlc_vars *hdlc, u32 features)
+{
+ memset(hdlc, 0, sizeof(struct isdnhdlc_vars));
+ if (features & HDLC_DCHANNEL) {
+ hdlc->dchannel = 1;
+ hdlc->state = HDLC_SEND_FIRST_FLAG;
+ } else {
+ hdlc->dchannel = 0;
+ hdlc->state = HDLC_SEND_FAST_FLAG;
+ hdlc->ffvalue = 0x7e;
+ }
+ hdlc->cbin = 0x7e;
+ if (features & HDLC_56KBIT) {
+ hdlc->do_adapt56 = 1;
+ hdlc->state = HDLC_SENDFLAG_B0;
+ } else
+ hdlc->data_bits = 8;
+ if (features & HDLC_BITREVERSE)
+ hdlc->do_bitreverse = 1;
+}
+EXPORT_SYMBOL(isdnhdlc_rcv_init);
+
+static int
+check_frame(struct isdnhdlc_vars *hdlc)
+{
+ int status;
+
+ if (hdlc->dstpos < 2) /* too small - framing error */
+ status = -HDLC_FRAMING_ERROR;
+ else if (hdlc->crc != 0xf0b8) /* crc error */
+ status = -HDLC_CRC_ERROR;
+ else {
+ /* remove CRC */
+ hdlc->dstpos -= 2;
+ /* good frame */
+ status = hdlc->dstpos;
+ }
+ return status;
+}
+
+/*
+ isdnhdlc_decode - decodes HDLC frames from a transparent bit stream.
+
+ The source buffer is scanned for valid HDLC frames looking for
+ flags (01111110) to indicate the start of a frame. If the start of
+ the frame is found, the bit stuffing is removed (0 after 5 1's).
+ When a new flag is found, the complete frame has been received
+ and the CRC is checked.
+ If a valid frame is found, the function returns the frame length
+ excluding the CRC with the bit HDLC_END_OF_FRAME set.
+ If the beginning of a valid frame is found, the function returns
+ the length.
+ If a framing error is found (too many 1s and not a flag) the function
+ returns the length with the bit HDLC_FRAMING_ERROR set.
+ If a CRC error is found the function returns the length with the
+ bit HDLC_CRC_ERROR set.
+ If the frame length exceeds the destination buffer size, the function
+ returns the length with the bit HDLC_LENGTH_ERROR set.
+
+ src - source buffer
+ slen - source buffer length
+ count - number of bytes removed (decoded) from the source buffer
+ dst _ destination buffer
+ dsize - destination buffer size
+ returns - number of decoded bytes in the destination buffer and status
+ flag.
+*/
+int isdnhdlc_decode(struct isdnhdlc_vars *hdlc, const u8 *src, int slen,
+ int *count, u8 *dst, int dsize)
+{
+ int status = 0;
+
+ static const unsigned char fast_flag[] = {
+ 0x00, 0x00, 0x00, 0x20, 0x30, 0x38, 0x3c, 0x3e, 0x3f
+ };
+
+ static const unsigned char fast_flag_value[] = {
+ 0x00, 0x7e, 0xfc, 0xf9, 0xf3, 0xe7, 0xcf, 0x9f, 0x3f
+ };
+
+ static const unsigned char fast_abort[] = {
+ 0x00, 0x00, 0x80, 0xc0, 0xe0, 0xf0, 0xf8, 0xfc, 0xfe, 0xff
+ };
+
+#define handle_fast_flag(h) \
+ do { \
+ if (h->cbin == fast_flag[h->bit_shift]) { \
+ h->ffvalue = fast_flag_value[h->bit_shift]; \
+ h->state = HDLC_FAST_FLAG; \
+ h->ffbit_shift = h->bit_shift; \
+ h->bit_shift = 1; \
+ } else { \
+ h->state = HDLC_GET_DATA; \
+ h->data_received = 0; \
+ } \
+ } while (0)
+
+#define handle_abort(h) \
+ do { \
+ h->shift_reg = fast_abort[h->ffbit_shift - 1]; \
+ h->hdlc_bits1 = h->ffbit_shift - 2; \
+ if (h->hdlc_bits1 < 0) \
+ h->hdlc_bits1 = 0; \
+ h->data_bits = h->ffbit_shift - 1; \
+ h->state = HDLC_GET_DATA; \
+ h->data_received = 0; \
+ } while (0)
+
+ *count = slen;
+
+ while (slen > 0) {
+ if (hdlc->bit_shift == 0) {
+ /* the code is for bitreverse streams */
+ if (hdlc->do_bitreverse == 0)
+ hdlc->cbin = bitrev8(*src++);
+ else
+ hdlc->cbin = *src++;
+ slen--;
+ hdlc->bit_shift = 8;
+ if (hdlc->do_adapt56)
+ hdlc->bit_shift--;
+ }
+
+ switch (hdlc->state) {
+ case STOPPED:
+ return 0;
+ case HDLC_FAST_IDLE:
+ if (hdlc->cbin == 0xff) {
+ hdlc->bit_shift = 0;
+ break;
+ }
+ hdlc->state = HDLC_GET_FLAG_B0;
+ hdlc->hdlc_bits1 = 0;
+ hdlc->bit_shift = 8;
+ break;
+ case HDLC_GET_FLAG_B0:
+ if (!(hdlc->cbin & 0x80)) {
+ hdlc->state = HDLC_GETFLAG_B1A6;
+ hdlc->hdlc_bits1 = 0;
+ } else {
+ if ((!hdlc->do_adapt56) &&
+ (++hdlc->hdlc_bits1 >= 8) &&
+ (hdlc->bit_shift == 1))
+ hdlc->state = HDLC_FAST_IDLE;
+ }
+ hdlc->cbin <<= 1;
+ hdlc->bit_shift--;
+ break;
+ case HDLC_GETFLAG_B1A6:
+ if (hdlc->cbin & 0x80) {
+ hdlc->hdlc_bits1++;
+ if (hdlc->hdlc_bits1 == 6)
+ hdlc->state = HDLC_GETFLAG_B7;
+ } else
+ hdlc->hdlc_bits1 = 0;
+ hdlc->cbin <<= 1;
+ hdlc->bit_shift--;
+ break;
+ case HDLC_GETFLAG_B7:
+ if (hdlc->cbin & 0x80) {
+ hdlc->state = HDLC_GET_FLAG_B0;
+ } else {
+ hdlc->state = HDLC_GET_DATA;
+ hdlc->crc = 0xffff;
+ hdlc->shift_reg = 0;
+ hdlc->hdlc_bits1 = 0;
+ hdlc->data_bits = 0;
+ hdlc->data_received = 0;
+ }
+ hdlc->cbin <<= 1;
+ hdlc->bit_shift--;
+ break;
+ case HDLC_GET_DATA:
+ if (hdlc->cbin & 0x80) {
+ hdlc->hdlc_bits1++;
+ switch (hdlc->hdlc_bits1) {
+ case 6:
+ break;
+ case 7:
+ if (hdlc->data_received)
+ /* bad frame */
+ status = -HDLC_FRAMING_ERROR;
+ if (!hdlc->do_adapt56) {
+ if (hdlc->cbin == fast_abort
+ [hdlc->bit_shift + 1]) {
+ hdlc->state =
+ HDLC_FAST_IDLE;
+ hdlc->bit_shift = 1;
+ break;
+ }
+ } else
+ hdlc->state = HDLC_GET_FLAG_B0;
+ break;
+ default:
+ hdlc->shift_reg >>= 1;
+ hdlc->shift_reg |= 0x80;
+ hdlc->data_bits++;
+ break;
+ }
+ } else {
+ switch (hdlc->hdlc_bits1) {
+ case 5:
+ break;
+ case 6:
+ if (hdlc->data_received)
+ status = check_frame(hdlc);
+ hdlc->crc = 0xffff;
+ hdlc->shift_reg = 0;
+ hdlc->data_bits = 0;
+ if (!hdlc->do_adapt56)
+ handle_fast_flag(hdlc);
+ else {
+ hdlc->state = HDLC_GET_DATA;
+ hdlc->data_received = 0;
+ }
+ break;
+ default:
+ hdlc->shift_reg >>= 1;
+ hdlc->data_bits++;
+ break;
+ }
+ hdlc->hdlc_bits1 = 0;
+ }
+ if (status) {
+ hdlc->dstpos = 0;
+ *count -= slen;
+ hdlc->cbin <<= 1;
+ hdlc->bit_shift--;
+ return status;
+ }
+ if (hdlc->data_bits == 8) {
+ hdlc->data_bits = 0;
+ hdlc->data_received = 1;
+ hdlc->crc = crc_ccitt_byte(hdlc->crc,
+ hdlc->shift_reg);
+
+ /* good byte received */
+ if (hdlc->dstpos < dsize)
+ dst[hdlc->dstpos++] = hdlc->shift_reg;
+ else {
+ /* frame too long */
+ status = -HDLC_LENGTH_ERROR;
+ hdlc->dstpos = 0;
+ }
+ }
+ hdlc->cbin <<= 1;
+ hdlc->bit_shift--;
+ break;
+ case HDLC_FAST_FLAG:
+ if (hdlc->cbin == hdlc->ffvalue) {
+ hdlc->bit_shift = 0;
+ break;
+ } else {
+ if (hdlc->cbin == 0xff) {
+ hdlc->state = HDLC_FAST_IDLE;
+ hdlc->bit_shift = 0;
+ } else if (hdlc->ffbit_shift == 8) {
+ hdlc->state = HDLC_GETFLAG_B7;
+ break;
+ } else
+ handle_abort(hdlc);
+ }
+ break;
+ default:
+ break;
+ }
+ }
+ *count -= slen;
+ return 0;
+}
+EXPORT_SYMBOL(isdnhdlc_decode);
+/*
+ isdnhdlc_encode - encodes HDLC frames to a transparent bit stream.
+
+ The bit stream starts with a beginning flag (01111110). After
+ that each byte is added to the bit stream with bit stuffing added
+ (0 after 5 1's).
+ When the last byte has been removed from the source buffer, the
+ CRC (2 bytes is added) and the frame terminates with the ending flag.
+ For the dchannel, the idle character (all 1's) is also added at the end.
+ If this function is called with empty source buffer (slen=0), flags or
+ idle character will be generated.
+
+ src - source buffer
+ slen - source buffer length
+ count - number of bytes removed (encoded) from source buffer
+ dst _ destination buffer
+ dsize - destination buffer size
+ returns - number of encoded bytes in the destination buffer
+*/
+int isdnhdlc_encode(struct isdnhdlc_vars *hdlc, const u8 *src, u16 slen,
+ int *count, u8 *dst, int dsize)
+{
+ static const unsigned char xfast_flag_value[] = {
+ 0x7e, 0x3f, 0x9f, 0xcf, 0xe7, 0xf3, 0xf9, 0xfc, 0x7e
+ };
+
+ int len = 0;
+
+ *count = slen;
+
+ /* special handling for one byte frames */
+ if ((slen == 1) && (hdlc->state == HDLC_SEND_FAST_FLAG))
+ hdlc->state = HDLC_SENDFLAG_ONE;
+ while (dsize > 0) {
+ if (hdlc->bit_shift == 0) {
+ if (slen && !hdlc->do_closing) {
+ hdlc->shift_reg = *src++;
+ slen--;
+ if (slen == 0)
+ /* closing sequence, CRC + flag(s) */
+ hdlc->do_closing = 1;
+ hdlc->bit_shift = 8;
+ } else {
+ if (hdlc->state == HDLC_SEND_DATA) {
+ if (hdlc->data_received) {
+ hdlc->state = HDLC_SEND_CRC1;
+ hdlc->crc ^= 0xffff;
+ hdlc->bit_shift = 8;
+ hdlc->shift_reg =
+ hdlc->crc & 0xff;
+ } else if (!hdlc->do_adapt56)
+ hdlc->state =
+ HDLC_SEND_FAST_FLAG;
+ else
+ hdlc->state =
+ HDLC_SENDFLAG_B0;
+ }
+
+ }
+ }
+
+ switch (hdlc->state) {
+ case STOPPED:
+ while (dsize--)
+ *dst++ = 0xff;
+ return dsize;
+ case HDLC_SEND_FAST_FLAG:
+ hdlc->do_closing = 0;
+ if (slen == 0) {
+ /* the code is for bitreverse streams */
+ if (hdlc->do_bitreverse == 0)
+ *dst++ = bitrev8(hdlc->ffvalue);
+ else
+ *dst++ = hdlc->ffvalue;
+ len++;
+ dsize--;
+ break;
+ }
+ /* fall through */
+ case HDLC_SENDFLAG_ONE:
+ if (hdlc->bit_shift == 8) {
+ hdlc->cbin = hdlc->ffvalue >>
+ (8 - hdlc->data_bits);
+ hdlc->state = HDLC_SEND_DATA;
+ hdlc->crc = 0xffff;
+ hdlc->hdlc_bits1 = 0;
+ hdlc->data_received = 1;
+ }
+ break;
+ case HDLC_SENDFLAG_B0:
+ hdlc->do_closing = 0;
+ hdlc->cbin <<= 1;
+ hdlc->data_bits++;
+ hdlc->hdlc_bits1 = 0;
+ hdlc->state = HDLC_SENDFLAG_B1A6;
+ break;
+ case HDLC_SENDFLAG_B1A6:
+ hdlc->cbin <<= 1;
+ hdlc->data_bits++;
+ hdlc->cbin++;
+ if (++hdlc->hdlc_bits1 == 6)
+ hdlc->state = HDLC_SENDFLAG_B7;
+ break;
+ case HDLC_SENDFLAG_B7:
+ hdlc->cbin <<= 1;
+ hdlc->data_bits++;
+ if (slen == 0) {
+ hdlc->state = HDLC_SENDFLAG_B0;
+ break;
+ }
+ if (hdlc->bit_shift == 8) {
+ hdlc->state = HDLC_SEND_DATA;
+ hdlc->crc = 0xffff;
+ hdlc->hdlc_bits1 = 0;
+ hdlc->data_received = 1;
+ }
+ break;
+ case HDLC_SEND_FIRST_FLAG:
+ hdlc->data_received = 1;
+ if (hdlc->data_bits == 8) {
+ hdlc->state = HDLC_SEND_DATA;
+ hdlc->crc = 0xffff;
+ hdlc->hdlc_bits1 = 0;
+ break;
+ }
+ hdlc->cbin <<= 1;
+ hdlc->data_bits++;
+ if (hdlc->shift_reg & 0x01)
+ hdlc->cbin++;
+ hdlc->shift_reg >>= 1;
+ hdlc->bit_shift--;
+ if (hdlc->bit_shift == 0) {
+ hdlc->state = HDLC_SEND_DATA;
+ hdlc->crc = 0xffff;
+ hdlc->hdlc_bits1 = 0;
+ }
+ break;
+ case HDLC_SEND_DATA:
+ hdlc->cbin <<= 1;
+ hdlc->data_bits++;
+ if (hdlc->hdlc_bits1 == 5) {
+ hdlc->hdlc_bits1 = 0;
+ break;
+ }
+ if (hdlc->bit_shift == 8)
+ hdlc->crc = crc_ccitt_byte(hdlc->crc,
+ hdlc->shift_reg);
+ if (hdlc->shift_reg & 0x01) {
+ hdlc->hdlc_bits1++;
+ hdlc->cbin++;
+ hdlc->shift_reg >>= 1;
+ hdlc->bit_shift--;
+ } else {
+ hdlc->hdlc_bits1 = 0;
+ hdlc->shift_reg >>= 1;
+ hdlc->bit_shift--;
+ }
+ break;
+ case HDLC_SEND_CRC1:
+ hdlc->cbin <<= 1;
+ hdlc->data_bits++;
+ if (hdlc->hdlc_bits1 == 5) {
+ hdlc->hdlc_bits1 = 0;
+ break;
+ }
+ if (hdlc->shift_reg & 0x01) {
+ hdlc->hdlc_bits1++;
+ hdlc->cbin++;
+ hdlc->shift_reg >>= 1;
+ hdlc->bit_shift--;
+ } else {
+ hdlc->hdlc_bits1 = 0;
+ hdlc->shift_reg >>= 1;
+ hdlc->bit_shift--;
+ }
+ if (hdlc->bit_shift == 0) {
+ hdlc->shift_reg = (hdlc->crc >> 8);
+ hdlc->state = HDLC_SEND_CRC2;
+ hdlc->bit_shift = 8;
+ }
+ break;
+ case HDLC_SEND_CRC2:
+ hdlc->cbin <<= 1;
+ hdlc->data_bits++;
+ if (hdlc->hdlc_bits1 == 5) {
+ hdlc->hdlc_bits1 = 0;
+ break;
+ }
+ if (hdlc->shift_reg & 0x01) {
+ hdlc->hdlc_bits1++;
+ hdlc->cbin++;
+ hdlc->shift_reg >>= 1;
+ hdlc->bit_shift--;
+ } else {
+ hdlc->hdlc_bits1 = 0;
+ hdlc->shift_reg >>= 1;
+ hdlc->bit_shift--;
+ }
+ if (hdlc->bit_shift == 0) {
+ hdlc->shift_reg = 0x7e;
+ hdlc->state = HDLC_SEND_CLOSING_FLAG;
+ hdlc->bit_shift = 8;
+ }
+ break;
+ case HDLC_SEND_CLOSING_FLAG:
+ hdlc->cbin <<= 1;
+ hdlc->data_bits++;
+ if (hdlc->hdlc_bits1 == 5) {
+ hdlc->hdlc_bits1 = 0;
+ break;
+ }
+ if (hdlc->shift_reg & 0x01)
+ hdlc->cbin++;
+ hdlc->shift_reg >>= 1;
+ hdlc->bit_shift--;
+ if (hdlc->bit_shift == 0) {
+ hdlc->ffvalue =
+ xfast_flag_value[hdlc->data_bits];
+ if (hdlc->dchannel) {
+ hdlc->ffvalue = 0x7e;
+ hdlc->state = HDLC_SEND_IDLE1;
+ hdlc->bit_shift = 8-hdlc->data_bits;
+ if (hdlc->bit_shift == 0)
+ hdlc->state =
+ HDLC_SEND_FAST_IDLE;
+ } else {
+ if (!hdlc->do_adapt56) {
+ hdlc->state =
+ HDLC_SEND_FAST_FLAG;
+ hdlc->data_received = 0;
+ } else {
+ hdlc->state = HDLC_SENDFLAG_B0;
+ hdlc->data_received = 0;
+ }
+ /* Finished this frame, send flags */
+ if (dsize > 1)
+ dsize = 1;
+ }
+ }
+ break;
+ case HDLC_SEND_IDLE1:
+ hdlc->do_closing = 0;
+ hdlc->cbin <<= 1;
+ hdlc->cbin++;
+ hdlc->data_bits++;
+ hdlc->bit_shift--;
+ if (hdlc->bit_shift == 0) {
+ hdlc->state = HDLC_SEND_FAST_IDLE;
+ hdlc->bit_shift = 0;
+ }
+ break;
+ case HDLC_SEND_FAST_IDLE:
+ hdlc->do_closing = 0;
+ hdlc->cbin = 0xff;
+ hdlc->data_bits = 8;
+ if (hdlc->bit_shift == 8) {
+ hdlc->cbin = 0x7e;
+ hdlc->state = HDLC_SEND_FIRST_FLAG;
+ } else {
+ /* the code is for bitreverse streams */
+ if (hdlc->do_bitreverse == 0)
+ *dst++ = bitrev8(hdlc->cbin);
+ else
+ *dst++ = hdlc->cbin;
+ hdlc->bit_shift = 0;
+ hdlc->data_bits = 0;
+ len++;
+ dsize = 0;
+ }
+ break;
+ default:
+ break;
+ }
+ if (hdlc->do_adapt56) {
+ if (hdlc->data_bits == 7) {
+ hdlc->cbin <<= 1;
+ hdlc->cbin++;
+ hdlc->data_bits++;
+ }
+ }
+ if (hdlc->data_bits == 8) {
+ /* the code is for bitreverse streams */
+ if (hdlc->do_bitreverse == 0)
+ *dst++ = bitrev8(hdlc->cbin);
+ else
+ *dst++ = hdlc->cbin;
+ hdlc->data_bits = 0;
+ len++;
+ dsize--;
+ }
+ }
+ *count -= slen;
+
+ return len;
+}
+EXPORT_SYMBOL(isdnhdlc_encode);
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-11 22:31:10 +0000