1// SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
  2/*
  3 *   Copyright (c) 2011, 2012, Atheros Communications Inc.
  4 *   Copyright (c) 2014, I2SE GmbH
  5 */
  6
  7/*   Atheros ethernet framing. Every Ethernet frame is surrounded
  8 *   by an atheros frame while transmitted over a serial channel;
  9 */
 10
 11#include <linux/init.h>
 12#include <linux/kernel.h>
 13#include <linux/module.h>
 14
 15#include "qca_7k_common.h"
 16
 17u16
 18qcafrm_create_header(u8 *buf, u16 length)
 19{
 20	__le16 len;
 21
 22	if (!buf)
 23		return 0;
 24
 25	len = cpu_to_le16(length);
 26
 27	buf[0] = 0xAA;
 28	buf[1] = 0xAA;
 29	buf[2] = 0xAA;
 30	buf[3] = 0xAA;
 31	buf[4] = len & 0xff;
 32	buf[5] = (len >> 8) & 0xff;
 33	buf[6] = 0;
 34	buf[7] = 0;
 35
 36	return QCAFRM_HEADER_LEN;
 37}
 38EXPORT_SYMBOL_GPL(qcafrm_create_header);
 39
 40u16
 41qcafrm_create_footer(u8 *buf)
 42{
 43	if (!buf)
 44		return 0;
 45
 46	buf[0] = 0x55;
 47	buf[1] = 0x55;
 48	return QCAFRM_FOOTER_LEN;
 49}
 50EXPORT_SYMBOL_GPL(qcafrm_create_footer);
 51
 52/*   Gather received bytes and try to extract a full ethernet frame by
 53 *   following a simple state machine.
 54 *
 55 * Return:   QCAFRM_GATHER       No ethernet frame fully received yet.
 56 *           QCAFRM_NOHEAD       Header expected but not found.
 57 *           QCAFRM_INVLEN       Atheros frame length is invalid
 58 *           QCAFRM_NOTAIL       Footer expected but not found.
 59 *           > 0                 Number of byte in the fully received
 60 *                               Ethernet frame
 61 */
 62
 63s32
 64qcafrm_fsm_decode(struct qcafrm_handle *handle, u8 *buf, u16 buf_len, u8 recv_byte)
 65{
 66	s32 ret = QCAFRM_GATHER;
 67	u16 len;
 68
 69	switch (handle->state) {
 70	case QCAFRM_HW_LEN0:
 71	case QCAFRM_HW_LEN1:
 72		/* by default, just go to next state */
 73		handle->state--;
 74
 75		if (recv_byte != 0x00) {
 76			/* first two bytes of length must be 0 */
 77			handle->state = handle->init;
 78		}
 79		break;
 80	case QCAFRM_HW_LEN2:
 81	case QCAFRM_HW_LEN3:
 82		handle->state--;
 83		break;
 84	/* 4 bytes header pattern */
 85	case QCAFRM_WAIT_AA1:
 86	case QCAFRM_WAIT_AA2:
 87	case QCAFRM_WAIT_AA3:
 88	case QCAFRM_WAIT_AA4:
 89		if (recv_byte != 0xAA) {
 90			ret = QCAFRM_NOHEAD;
 91			handle->state = handle->init;
 92		} else {
 93			handle->state--;
 94		}
 95		break;
 96		/* 2 bytes length. */
 97		/* Borrow offset field to hold length for now. */
 98	case QCAFRM_WAIT_LEN_BYTE0:
 99		handle->offset = recv_byte;
100		handle->state = QCAFRM_WAIT_LEN_BYTE1;
101		break;
102	case QCAFRM_WAIT_LEN_BYTE1:
103		handle->offset = handle->offset | (recv_byte << 8);
104		handle->state = QCAFRM_WAIT_RSVD_BYTE1;
105		break;
106	case QCAFRM_WAIT_RSVD_BYTE1:
107		handle->state = QCAFRM_WAIT_RSVD_BYTE2;
108		break;
109	case QCAFRM_WAIT_RSVD_BYTE2:
110		len = handle->offset;
111		if (len > buf_len || len < QCAFRM_MIN_LEN) {
112			ret = QCAFRM_INVLEN;
113			handle->state = handle->init;
114		} else {
115			handle->state = (enum qcafrm_state)(len + 1);
116			/* Remaining number of bytes. */
117			handle->offset = 0;
118		}
119		break;
120	default:
121		/* Receiving Ethernet frame itself. */
122		buf[handle->offset] = recv_byte;
123		handle->offset++;
124		handle->state--;
125		break;
126	case QCAFRM_WAIT_551:
127		if (recv_byte != 0x55) {
128			ret = QCAFRM_NOTAIL;
129			handle->state = handle->init;
130		} else {
131			handle->state = QCAFRM_WAIT_552;
132		}
133		break;
134	case QCAFRM_WAIT_552:
135		if (recv_byte != 0x55) {
136			ret = QCAFRM_NOTAIL;
137			handle->state = handle->init;
138		} else {
139			ret = handle->offset;
140			/* Frame is fully received. */
141			handle->state = handle->init;
142		}
143		break;
144	}
145
146	return ret;
147}
148EXPORT_SYMBOL_GPL(qcafrm_fsm_decode);
149
150MODULE_DESCRIPTION("Qualcomm Atheros QCA7000 common");
151MODULE_AUTHOR("Qualcomm Atheros Communications");
152MODULE_AUTHOR("Stefan Wahren <wahrenst@gmx.net>");
153MODULE_LICENSE("Dual BSD/GPL");