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/* SPDX-License-Identifier: GPL-2.0+ */
/*
* SSH message builder functions.
*
* Copyright (C) 2019-2022 Maximilian Luz <luzmaximilian@gmail.com>
*/
#ifndef _SURFACE_AGGREGATOR_SSH_MSGB_H
#define _SURFACE_AGGREGATOR_SSH_MSGB_H
#include <linux/unaligned.h>
#include <linux/types.h>
#include <linux/surface_aggregator/controller.h>
#include <linux/surface_aggregator/serial_hub.h>
/**
* struct msgbuf - Buffer struct to construct SSH messages.
* @begin: Pointer to the beginning of the allocated buffer space.
* @end: Pointer to the end (one past last element) of the allocated buffer
* space.
* @ptr: Pointer to the first free element in the buffer.
*/
struct msgbuf {
u8 *begin;
u8 *end;
u8 *ptr;
};
/**
* msgb_init() - Initialize the given message buffer struct.
* @msgb: The buffer struct to initialize
* @ptr: Pointer to the underlying memory by which the buffer will be backed.
* @cap: Size of the underlying memory.
*
* Initialize the given message buffer struct using the provided memory as
* backing.
*/
static inline void msgb_init(struct msgbuf *msgb, u8 *ptr, size_t cap)
{
msgb->begin = ptr;
msgb->end = ptr + cap;
msgb->ptr = ptr;
}
/**
* msgb_bytes_used() - Return the current number of bytes used in the buffer.
* @msgb: The message buffer.
*/
static inline size_t msgb_bytes_used(const struct msgbuf *msgb)
{
return msgb->ptr - msgb->begin;
}
static inline void __msgb_push_u8(struct msgbuf *msgb, u8 value)
{
*msgb->ptr = value;
msgb->ptr += sizeof(u8);
}
static inline void __msgb_push_u16(struct msgbuf *msgb, u16 value)
{
put_unaligned_le16(value, msgb->ptr);
msgb->ptr += sizeof(u16);
}
/**
* msgb_push_u16() - Push a u16 value to the buffer.
* @msgb: The message buffer.
* @value: The value to push to the buffer.
*/
static inline void msgb_push_u16(struct msgbuf *msgb, u16 value)
{
if (WARN_ON(msgb->ptr + sizeof(u16) > msgb->end))
return;
__msgb_push_u16(msgb, value);
}
/**
* msgb_push_syn() - Push SSH SYN bytes to the buffer.
* @msgb: The message buffer.
*/
static inline void msgb_push_syn(struct msgbuf *msgb)
{
msgb_push_u16(msgb, SSH_MSG_SYN);
}
/**
* msgb_push_buf() - Push raw data to the buffer.
* @msgb: The message buffer.
* @buf: The data to push to the buffer.
* @len: The length of the data to push to the buffer.
*/
static inline void msgb_push_buf(struct msgbuf *msgb, const u8 *buf, size_t len)
{
msgb->ptr = memcpy(msgb->ptr, buf, len) + len;
}
/**
* msgb_push_crc() - Compute CRC and push it to the buffer.
* @msgb: The message buffer.
* @buf: The data for which the CRC should be computed.
* @len: The length of the data for which the CRC should be computed.
*/
static inline void msgb_push_crc(struct msgbuf *msgb, const u8 *buf, size_t len)
{
msgb_push_u16(msgb, ssh_crc(buf, len));
}
/**
* msgb_push_frame() - Push a SSH message frame header to the buffer.
* @msgb: The message buffer
* @ty: The type of the frame.
* @len: The length of the payload of the frame.
* @seq: The sequence ID of the frame/packet.
*/
static inline void msgb_push_frame(struct msgbuf *msgb, u8 ty, u16 len, u8 seq)
{
u8 *const begin = msgb->ptr;
if (WARN_ON(msgb->ptr + sizeof(struct ssh_frame) > msgb->end))
return;
__msgb_push_u8(msgb, ty); /* Frame type. */
__msgb_push_u16(msgb, len); /* Frame payload length. */
__msgb_push_u8(msgb, seq); /* Frame sequence ID. */
msgb_push_crc(msgb, begin, msgb->ptr - begin);
}
/**
* msgb_push_ack() - Push a SSH ACK frame to the buffer.
* @msgb: The message buffer
* @seq: The sequence ID of the frame/packet to be ACKed.
*/
static inline void msgb_push_ack(struct msgbuf *msgb, u8 seq)
{
/* SYN. */
msgb_push_syn(msgb);
/* ACK-type frame + CRC. */
msgb_push_frame(msgb, SSH_FRAME_TYPE_ACK, 0x00, seq);
/* Payload CRC (ACK-type frames do not have a payload). */
msgb_push_crc(msgb, msgb->ptr, 0);
}
/**
* msgb_push_nak() - Push a SSH NAK frame to the buffer.
* @msgb: The message buffer
*/
static inline void msgb_push_nak(struct msgbuf *msgb)
{
/* SYN. */
msgb_push_syn(msgb);
/* NAK-type frame + CRC. */
msgb_push_frame(msgb, SSH_FRAME_TYPE_NAK, 0x00, 0x00);
/* Payload CRC (ACK-type frames do not have a payload). */
msgb_push_crc(msgb, msgb->ptr, 0);
}
/**
* msgb_push_cmd() - Push a SSH command frame with payload to the buffer.
* @msgb: The message buffer.
* @seq: The sequence ID (SEQ) of the frame/packet.
* @rqid: The request ID (RQID) of the request contained in the frame.
* @rqst: The request to wrap in the frame.
*/
static inline void msgb_push_cmd(struct msgbuf *msgb, u8 seq, u16 rqid,
const struct ssam_request *rqst)
{
const u8 type = SSH_FRAME_TYPE_DATA_SEQ;
u8 *cmd;
/* SYN. */
msgb_push_syn(msgb);
/* Command frame + CRC. */
msgb_push_frame(msgb, type, sizeof(struct ssh_command) + rqst->length, seq);
/* Frame payload: Command struct + payload. */
if (WARN_ON(msgb->ptr + sizeof(struct ssh_command) > msgb->end))
return;
cmd = msgb->ptr;
__msgb_push_u8(msgb, SSH_PLD_TYPE_CMD); /* Payload type. */
__msgb_push_u8(msgb, rqst->target_category); /* Target category. */
__msgb_push_u8(msgb, rqst->target_id); /* Target ID. */
__msgb_push_u8(msgb, SSAM_SSH_TID_HOST); /* Source ID. */
__msgb_push_u8(msgb, rqst->instance_id); /* Instance ID. */
__msgb_push_u16(msgb, rqid); /* Request ID. */
__msgb_push_u8(msgb, rqst->command_id); /* Command ID. */
/* Command payload. */
msgb_push_buf(msgb, rqst->payload, rqst->length);
/* CRC for command struct + payload. */
msgb_push_crc(msgb, cmd, msgb->ptr - cmd);
}
#endif /* _SURFACE_AGGREGATOR_SSH_MSGB_H */
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