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1/* SPDX-License-Identifier: GPL-2.0+ */
2/*
3 * SSH message builder functions.
4 *
5 * Copyright (C) 2019-2022 Maximilian Luz <[email protected]>
6 */
7
8#ifndef _SURFACE_AGGREGATOR_SSH_MSGB_H
9#define _SURFACE_AGGREGATOR_SSH_MSGB_H
10
11#include <linux/unaligned.h>
12#include <linux/types.h>
13
14#include <linux/surface_aggregator/controller.h>
15#include <linux/surface_aggregator/serial_hub.h>
16
17/**
18 * struct msgbuf - Buffer struct to construct SSH messages.
19 * @begin: Pointer to the beginning of the allocated buffer space.
20 * @end: Pointer to the end (one past last element) of the allocated buffer
21 * space.
22 * @ptr: Pointer to the first free element in the buffer.
23 */
24struct msgbuf {
25 u8 *begin;
26 u8 *end;
27 u8 *ptr;
28};
29
30/**
31 * msgb_init() - Initialize the given message buffer struct.
32 * @msgb: The buffer struct to initialize
33 * @ptr: Pointer to the underlying memory by which the buffer will be backed.
34 * @cap: Size of the underlying memory.
35 *
36 * Initialize the given message buffer struct using the provided memory as
37 * backing.
38 */
39static inline void msgb_init(struct msgbuf *msgb, u8 *ptr, size_t cap)
40{
41 msgb->begin = ptr;
42 msgb->end = ptr + cap;
43 msgb->ptr = ptr;
44}
45
46/**
47 * msgb_bytes_used() - Return the current number of bytes used in the buffer.
48 * @msgb: The message buffer.
49 */
50static inline size_t msgb_bytes_used(const struct msgbuf *msgb)
51{
52 return msgb->ptr - msgb->begin;
53}
54
55static inline void __msgb_push_u8(struct msgbuf *msgb, u8 value)
56{
57 *msgb->ptr = value;
58 msgb->ptr += sizeof(u8);
59}
60
61static inline void __msgb_push_u16(struct msgbuf *msgb, u16 value)
62{
63 put_unaligned_le16(value, msgb->ptr);
64 msgb->ptr += sizeof(u16);
65}
66
67/**
68 * msgb_push_u16() - Push a u16 value to the buffer.
69 * @msgb: The message buffer.
70 * @value: The value to push to the buffer.
71 */
72static inline void msgb_push_u16(struct msgbuf *msgb, u16 value)
73{
74 if (WARN_ON(msgb->ptr + sizeof(u16) > msgb->end))
75 return;
76
77 __msgb_push_u16(msgb, value);
78}
79
80/**
81 * msgb_push_syn() - Push SSH SYN bytes to the buffer.
82 * @msgb: The message buffer.
83 */
84static inline void msgb_push_syn(struct msgbuf *msgb)
85{
86 msgb_push_u16(msgb, SSH_MSG_SYN);
87}
88
89/**
90 * msgb_push_buf() - Push raw data to the buffer.
91 * @msgb: The message buffer.
92 * @buf: The data to push to the buffer.
93 * @len: The length of the data to push to the buffer.
94 */
95static inline void msgb_push_buf(struct msgbuf *msgb, const u8 *buf, size_t len)
96{
97 msgb->ptr = memcpy(msgb->ptr, buf, len) + len;
98}
99
100/**
101 * msgb_push_crc() - Compute CRC and push it to the buffer.
102 * @msgb: The message buffer.
103 * @buf: The data for which the CRC should be computed.
104 * @len: The length of the data for which the CRC should be computed.
105 */
106static inline void msgb_push_crc(struct msgbuf *msgb, const u8 *buf, size_t len)
107{
108 msgb_push_u16(msgb, ssh_crc(buf, len));
109}
110
111/**
112 * msgb_push_frame() - Push a SSH message frame header to the buffer.
113 * @msgb: The message buffer
114 * @ty: The type of the frame.
115 * @len: The length of the payload of the frame.
116 * @seq: The sequence ID of the frame/packet.
117 */
118static inline void msgb_push_frame(struct msgbuf *msgb, u8 ty, u16 len, u8 seq)
119{
120 u8 *const begin = msgb->ptr;
121
122 if (WARN_ON(msgb->ptr + sizeof(struct ssh_frame) > msgb->end))
123 return;
124
125 __msgb_push_u8(msgb, ty); /* Frame type. */
126 __msgb_push_u16(msgb, len); /* Frame payload length. */
127 __msgb_push_u8(msgb, seq); /* Frame sequence ID. */
128
129 msgb_push_crc(msgb, begin, msgb->ptr - begin);
130}
131
132/**
133 * msgb_push_ack() - Push a SSH ACK frame to the buffer.
134 * @msgb: The message buffer
135 * @seq: The sequence ID of the frame/packet to be ACKed.
136 */
137static inline void msgb_push_ack(struct msgbuf *msgb, u8 seq)
138{
139 /* SYN. */
140 msgb_push_syn(msgb);
141
142 /* ACK-type frame + CRC. */
143 msgb_push_frame(msgb, SSH_FRAME_TYPE_ACK, 0x00, seq);
144
145 /* Payload CRC (ACK-type frames do not have a payload). */
146 msgb_push_crc(msgb, msgb->ptr, 0);
147}
148
149/**
150 * msgb_push_nak() - Push a SSH NAK frame to the buffer.
151 * @msgb: The message buffer
152 */
153static inline void msgb_push_nak(struct msgbuf *msgb)
154{
155 /* SYN. */
156 msgb_push_syn(msgb);
157
158 /* NAK-type frame + CRC. */
159 msgb_push_frame(msgb, SSH_FRAME_TYPE_NAK, 0x00, 0x00);
160
161 /* Payload CRC (ACK-type frames do not have a payload). */
162 msgb_push_crc(msgb, msgb->ptr, 0);
163}
164
165/**
166 * msgb_push_cmd() - Push a SSH command frame with payload to the buffer.
167 * @msgb: The message buffer.
168 * @seq: The sequence ID (SEQ) of the frame/packet.
169 * @rqid: The request ID (RQID) of the request contained in the frame.
170 * @rqst: The request to wrap in the frame.
171 */
172static inline void msgb_push_cmd(struct msgbuf *msgb, u8 seq, u16 rqid,
173 const struct ssam_request *rqst)
174{
175 const u8 type = SSH_FRAME_TYPE_DATA_SEQ;
176 u8 *cmd;
177
178 /* SYN. */
179 msgb_push_syn(msgb);
180
181 /* Command frame + CRC. */
182 msgb_push_frame(msgb, type, sizeof(struct ssh_command) + rqst->length, seq);
183
184 /* Frame payload: Command struct + payload. */
185 if (WARN_ON(msgb->ptr + sizeof(struct ssh_command) > msgb->end))
186 return;
187
188 cmd = msgb->ptr;
189
190 __msgb_push_u8(msgb, SSH_PLD_TYPE_CMD); /* Payload type. */
191 __msgb_push_u8(msgb, rqst->target_category); /* Target category. */
192 __msgb_push_u8(msgb, rqst->target_id); /* Target ID. */
193 __msgb_push_u8(msgb, SSAM_SSH_TID_HOST); /* Source ID. */
194 __msgb_push_u8(msgb, rqst->instance_id); /* Instance ID. */
195 __msgb_push_u16(msgb, rqid); /* Request ID. */
196 __msgb_push_u8(msgb, rqst->command_id); /* Command ID. */
197
198 /* Command payload. */
199 msgb_push_buf(msgb, rqst->payload, rqst->length);
200
201 /* CRC for command struct + payload. */
202 msgb_push_crc(msgb, cmd, msgb->ptr - cmd);
203}
204
205#endif /* _SURFACE_AGGREGATOR_SSH_MSGB_H */