1/* SPDX-License-Identifier: GPL-2.0+ */
  2/*
  3 * SSH message parser.
  4 *
  5 * Copyright (C) 2019-2022 Maximilian Luz <luzmaximilian@gmail.com>
  6 */
  7
  8#ifndef _SURFACE_AGGREGATOR_SSH_PARSER_H
  9#define _SURFACE_AGGREGATOR_SSH_PARSER_H
 10
 11#include <linux/device.h>
 12#include <linux/kfifo.h>
 13#include <linux/slab.h>
 14#include <linux/types.h>
 15
 16#include <linux/surface_aggregator/serial_hub.h>
 17
 18/**
 19 * struct sshp_buf - Parser buffer for SSH messages.
 20 * @ptr: Pointer to the beginning of the buffer.
 21 * @len: Number of bytes used in the buffer.
 22 * @cap: Maximum capacity of the buffer.
 23 */
 24struct sshp_buf {
 25	u8    *ptr;
 26	size_t len;
 27	size_t cap;
 28};
 29
 30/**
 31 * sshp_buf_init() - Initialize a SSH parser buffer.
 32 * @buf: The buffer to initialize.
 33 * @ptr: The memory backing the buffer.
 34 * @cap: The length of the memory backing the buffer, i.e. its capacity.
 35 *
 36 * Initializes the buffer with the given memory as backing and set its used
 37 * length to zero.
 38 */
 39static inline void sshp_buf_init(struct sshp_buf *buf, u8 *ptr, size_t cap)
 40{
 41	buf->ptr = ptr;
 42	buf->len = 0;
 43	buf->cap = cap;
 44}
 45
 46/**
 47 * sshp_buf_alloc() - Allocate and initialize a SSH parser buffer.
 48 * @buf:   The buffer to initialize/allocate to.
 49 * @cap:   The desired capacity of the buffer.
 50 * @flags: The flags used for allocating the memory.
 51 *
 52 * Allocates @cap bytes and initializes the provided buffer struct with the
 53 * allocated memory.
 54 *
 55 * Return: Returns zero on success and %-ENOMEM if allocation failed.
 56 */
 57static inline int sshp_buf_alloc(struct sshp_buf *buf, size_t cap, gfp_t flags)
 58{
 59	u8 *ptr;
 60
 61	ptr = kzalloc(cap, flags);
 62	if (!ptr)
 63		return -ENOMEM;
 64
 65	sshp_buf_init(buf, ptr, cap);
 66	return 0;
 67}
 68
 69/**
 70 * sshp_buf_free() - Free a SSH parser buffer.
 71 * @buf: The buffer to free.
 72 *
 73 * Frees a SSH parser buffer by freeing the memory backing it and then
 74 * resetting its pointer to %NULL and length and capacity to zero. Intended to
 75 * free a buffer previously allocated with sshp_buf_alloc().
 76 */
 77static inline void sshp_buf_free(struct sshp_buf *buf)
 78{
 79	kfree(buf->ptr);
 80	buf->ptr = NULL;
 81	buf->len = 0;
 82	buf->cap = 0;
 83}
 84
 85/**
 86 * sshp_buf_drop() - Drop data from the beginning of the buffer.
 87 * @buf: The buffer to drop data from.
 88 * @n:   The number of bytes to drop.
 89 *
 90 * Drops the first @n bytes from the buffer. Re-aligns any remaining data to
 91 * the beginning of the buffer.
 92 */
 93static inline void sshp_buf_drop(struct sshp_buf *buf, size_t n)
 94{
 95	memmove(buf->ptr, buf->ptr + n, buf->len - n);
 96	buf->len -= n;
 97}
 98
 99/**
100 * sshp_buf_read_from_fifo() - Transfer data from a fifo to the buffer.
101 * @buf:  The buffer to write the data into.
102 * @fifo: The fifo to read the data from.
103 *
104 * Transfers the data contained in the fifo to the buffer, removing it from
105 * the fifo. This function will try to transfer as much data as possible,
106 * limited either by the remaining space in the buffer or by the number of
107 * bytes available in the fifo.
108 *
109 * Return: Returns the number of bytes transferred.
110 */
111static inline size_t sshp_buf_read_from_fifo(struct sshp_buf *buf,
112					     struct kfifo *fifo)
113{
114	size_t n;
115
116	n =  kfifo_out(fifo, buf->ptr + buf->len, buf->cap - buf->len);
117	buf->len += n;
118
119	return n;
120}
121
122/**
123 * sshp_buf_span_from() - Initialize a span from the given buffer and offset.
124 * @buf:    The buffer to create the span from.
125 * @offset: The offset in the buffer at which the span should start.
126 * @span:   The span to initialize (output).
127 *
128 * Initializes the provided span to point to the memory at the given offset in
129 * the buffer, with the length of the span being capped by the number of bytes
130 * used in the buffer after the offset (i.e. bytes remaining after the
131 * offset).
132 *
133 * Warning: This function does not validate that @offset is less than or equal
134 * to the number of bytes used in the buffer or the buffer capacity. This must
135 * be guaranteed by the caller.
136 */
137static inline void sshp_buf_span_from(struct sshp_buf *buf, size_t offset,
138				      struct ssam_span *span)
139{
140	span->ptr = buf->ptr + offset;
141	span->len = buf->len - offset;
142}
143
144bool sshp_find_syn(const struct ssam_span *src, struct ssam_span *rem);
145
146int sshp_parse_frame(const struct device *dev, const struct ssam_span *source,
147		     struct ssh_frame **frame, struct ssam_span *payload,
148		     size_t maxlen);
149
150int sshp_parse_command(const struct device *dev, const struct ssam_span *source,
151		       struct ssh_command **command,
152		       struct ssam_span *command_data);
153
154#endif /* _SURFACE_AGGREGATOR_SSH_PARSER_h */