1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3  * hdlc.h  --  General purpose ISDN HDLC decoder.
4  *
5  * Implementation of a HDLC decoder/encoder in software.
6  * Necessary because some ISDN devices don't have HDLC
7  * controllers.
8  *
9  * Copyright (C)
10  *	2009	Karsten Keil		<keil@b1-systems.de>
11  *	2002	Wolfgang Mües		<wolfgang@iksw-muees.de>
12  *	2001	Frode Isaksen		<fisaksen@bewan.com>
13  *	2001	Kai Germaschewski	<kai.germaschewski@gmx.de>
14  */
15 
16 #ifndef __ISDNHDLC_H__
17 #define __ISDNHDLC_H__
18 
19 struct isdnhdlc_vars {
20 	int bit_shift;
21 	int hdlc_bits1;
22 	int data_bits;
23 	int ffbit_shift;	/* encoding only */
24 	int state;
25 	int dstpos;
26 
27 	u16 crc;
28 
29 	u8 cbin;
30 	u8 shift_reg;
31 	u8 ffvalue;
32 
33 	/* set if transferring data */
34 	u32 data_received:1;
35 	/* set if D channel (send idle instead of flags) */
36 	u32 dchannel:1;
37 	/* set if 56K adaptation */
38 	u32 do_adapt56:1;
39 	/* set if in closing phase (need to send CRC + flag) */
40 	u32 do_closing:1;
41 	/* set if data is bitreverse */
42 	u32 do_bitreverse:1;
43 };
44 
45 /* Feature Flags */
46 #define HDLC_56KBIT	0x01
47 #define HDLC_DCHANNEL	0x02
48 #define HDLC_BITREVERSE	0x04
49 
50 /*
51   The return value from isdnhdlc_decode is
52   the frame length, 0 if no complete frame was decoded,
53   or a negative error number
54 */
55 #define HDLC_FRAMING_ERROR     1
56 #define HDLC_CRC_ERROR         2
57 #define HDLC_LENGTH_ERROR      3
58 
59 extern void	isdnhdlc_rcv_init(struct isdnhdlc_vars *hdlc, u32 features);
60 
61 extern int	isdnhdlc_decode(struct isdnhdlc_vars *hdlc, const u8 *src,
62 			int slen, int *count, u8 *dst, int dsize);
63 
64 extern void	isdnhdlc_out_init(struct isdnhdlc_vars *hdlc, u32 features);
65 
66 extern int	isdnhdlc_encode(struct isdnhdlc_vars *hdlc, const u8 *src,
67 			u16 slen, int *count, u8 *dst, int dsize);
68 
69 #endif /* __ISDNHDLC_H__ */
70