1 /*
2 * Copyright (c) 2011, 2012, Atheros Communications Inc.
3 * Copyright (c) 2014, I2SE GmbH
4 *
5 * Permission to use, copy, modify, and/or distribute this software
6 * for any purpose with or without fee is hereby granted, provided
7 * that the above copyright notice and this permission notice appear
8 * in all copies.
9 *
10 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
11 * WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
12 * WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
13 * THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR
14 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
15 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
16 * NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
17 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
18 */
19
20 /* Atheros ethernet framing. Every Ethernet frame is surrounded
21 * by an atheros frame while transmitted over a serial channel;
22 */
23
24 #include <linux/kernel.h>
25
26 #include "qca_framing.h"
27
28 u16
qcafrm_create_header(u8 * buf,u16 length)29 qcafrm_create_header(u8 *buf, u16 length)
30 {
31 __le16 len;
32
33 if (!buf)
34 return 0;
35
36 len = cpu_to_le16(length);
37
38 buf[0] = 0xAA;
39 buf[1] = 0xAA;
40 buf[2] = 0xAA;
41 buf[3] = 0xAA;
42 buf[4] = len & 0xff;
43 buf[5] = (len >> 8) & 0xff;
44 buf[6] = 0;
45 buf[7] = 0;
46
47 return QCAFRM_HEADER_LEN;
48 }
49
50 u16
qcafrm_create_footer(u8 * buf)51 qcafrm_create_footer(u8 *buf)
52 {
53 if (!buf)
54 return 0;
55
56 buf[0] = 0x55;
57 buf[1] = 0x55;
58 return QCAFRM_FOOTER_LEN;
59 }
60
61 /* Gather received bytes and try to extract a full ethernet frame by
62 * following a simple state machine.
63 *
64 * Return: QCAFRM_GATHER No ethernet frame fully received yet.
65 * QCAFRM_NOHEAD Header expected but not found.
66 * QCAFRM_INVLEN Atheros frame length is invalid
67 * QCAFRM_NOTAIL Footer expected but not found.
68 * > 0 Number of byte in the fully received
69 * Ethernet frame
70 */
71
72 s32
qcafrm_fsm_decode(struct qcafrm_handle * handle,u8 * buf,u16 buf_len,u8 recv_byte)73 qcafrm_fsm_decode(struct qcafrm_handle *handle, u8 *buf, u16 buf_len, u8 recv_byte)
74 {
75 s32 ret = QCAFRM_GATHER;
76 u16 len;
77
78 switch (handle->state) {
79 case QCAFRM_HW_LEN0:
80 case QCAFRM_HW_LEN1:
81 /* by default, just go to next state */
82 handle->state--;
83
84 if (recv_byte != 0x00) {
85 /* first two bytes of length must be 0 */
86 handle->state = QCAFRM_HW_LEN0;
87 }
88 break;
89 case QCAFRM_HW_LEN2:
90 case QCAFRM_HW_LEN3:
91 handle->state--;
92 break;
93 /* 4 bytes header pattern */
94 case QCAFRM_WAIT_AA1:
95 case QCAFRM_WAIT_AA2:
96 case QCAFRM_WAIT_AA3:
97 case QCAFRM_WAIT_AA4:
98 if (recv_byte != 0xAA) {
99 ret = QCAFRM_NOHEAD;
100 handle->state = QCAFRM_HW_LEN0;
101 } else {
102 handle->state--;
103 }
104 break;
105 /* 2 bytes length. */
106 /* Borrow offset field to hold length for now. */
107 case QCAFRM_WAIT_LEN_BYTE0:
108 handle->offset = recv_byte;
109 handle->state = QCAFRM_WAIT_LEN_BYTE1;
110 break;
111 case QCAFRM_WAIT_LEN_BYTE1:
112 handle->offset = handle->offset | (recv_byte << 8);
113 handle->state = QCAFRM_WAIT_RSVD_BYTE1;
114 break;
115 case QCAFRM_WAIT_RSVD_BYTE1:
116 handle->state = QCAFRM_WAIT_RSVD_BYTE2;
117 break;
118 case QCAFRM_WAIT_RSVD_BYTE2:
119 len = handle->offset;
120 if (len > buf_len || len < QCAFRM_ETHMINLEN) {
121 ret = QCAFRM_INVLEN;
122 handle->state = QCAFRM_HW_LEN0;
123 } else {
124 handle->state = (enum qcafrm_state)(len + 1);
125 /* Remaining number of bytes. */
126 handle->offset = 0;
127 }
128 break;
129 default:
130 /* Receiving Ethernet frame itself. */
131 buf[handle->offset] = recv_byte;
132 handle->offset++;
133 handle->state--;
134 break;
135 case QCAFRM_WAIT_551:
136 if (recv_byte != 0x55) {
137 ret = QCAFRM_NOTAIL;
138 handle->state = QCAFRM_HW_LEN0;
139 } else {
140 handle->state = QCAFRM_WAIT_552;
141 }
142 break;
143 case QCAFRM_WAIT_552:
144 if (recv_byte != 0x55) {
145 ret = QCAFRM_NOTAIL;
146 handle->state = QCAFRM_HW_LEN0;
147 } else {
148 ret = handle->offset;
149 /* Frame is fully received. */
150 handle->state = QCAFRM_HW_LEN0;
151 }
152 break;
153 }
154
155 return ret;
156 }
157