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  */
24 struct 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  */
sshp_buf_init(struct sshp_buf * buf,u8 * ptr,size_t cap)39 static 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  */
sshp_buf_alloc(struct sshp_buf * buf,size_t cap,gfp_t flags)57 static 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  */
sshp_buf_free(struct sshp_buf * buf)77 static 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  */
sshp_buf_drop(struct sshp_buf * buf,size_t n)93 static 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  */
sshp_buf_read_from_fifo(struct sshp_buf * buf,struct kfifo * fifo)111 static 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  */
sshp_buf_span_from(struct sshp_buf * buf,size_t offset,struct ssam_span * span)137 static 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 
144 bool sshp_find_syn(const struct ssam_span *src, struct ssam_span *rem);
145 
146 int 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 
150 int 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 */
155