src/libcamera/ipa_controls.cpp


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195

/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2019, Google Inc.
 *
 * ipa_controls.cpp - IPA control handling
 */

#include <libcamera/ipa/ipa_controls.h>

/**
 * \file ipa_controls.h
 * \brief Type definitions for serialized controls
 *
 * This file defines binary formats to store ControlList and ControlInfoMap
 * instances in contiguous, self-contained memory areas called control packets.
 * It describes the layout of the packets through a set of C structures. These
 * formats shall be used when serializing ControlList and ControlInfoMap to
 * transfer them through the IPA C interface and IPA IPC transports.
 *
 * A control packet contains a list of entries, each of them describing a single
 * control info or control value. The packet starts with a fixed-size header
 * described by the ipa_controls_header structure, followed by an array of
 * fixed-size entries. Each entry is associated with data, stored either
 * directly in the entry, or in a data section after the entries array.
 *
 * The following diagram describes the layout of the ControlList packet.
 *
 * ~~~~
 *           +-------------------------+    .                      .
 *  Header / | ipa_controls_header     |    |                      |
 *         | |                         |    |                      |
 *         \ |                         |    |                      |
 *           +-------------------------+    |                      |
 *         / | ipa_control_value_entry |    | hdr.data_offset      |
 *         | | #0                      |    |                      |
 * Control | +-------------------------+    |                      |
 *   value | | ...                     |    |                      |
 * entries | +-------------------------+    |                      |
 *         | | ipa_control_value_entry |    |             hdr.size |
 *         \ | #hdr.entries - 1        |    |                      |
 *           +-------------------------+    |                      |
 *           | empty space (optional)  |    |                      |
 *           +-------------------------+ <--´  .                   |
 *         / | ...                     |       | entry[n].offset   |
 *    Data | | ...                     |       |                   |
 * section | | value data for entry #n | <-----´                   |
 *         \ | ...                     |                           |
 *           +-------------------------+                           |
 *           | empty space (optional)  |                           |
 *           +-------------------------+ <-------------------------´
 * ~~~~
 *
 * The packet header contains the size of the packet, the number of entries, and
 * the offset from the beginning of the packet to the data section. The packet
 * entries array immediately follows the header. The data section starts at the
 * offset ipa_controls_header::data_offset from the beginning of the packet, and
 * shall be aligned to a multiple of 8 bytes.
 *
 * Entries are described by the ipa_control_value_entry structure. They contain
 * the numerical ID of the control, its type, and the number of control values.
 *
 * The control values are stored in the data section in the platform's native
 * format. The ipa_control_value_entry::offset field stores the offset from the
 * beginning of the data section to the values.
 *
 * All control values in the data section shall be stored in the same order as
 * the respective control entries, shall be aligned to a multiple of 8 bytes,
 * and shall be contiguous in memory.
 *
 * Empty spaces may be present between the end of the entries array and the
 * data section, and after the data section. They shall be ignored when parsing
 * the packet.
 *
 * The following diagram describes the layout of the ControlInfoMap packet.
 *
 * ~~~~
 *           +-------------------------+    .                      .
 *  Header / | ipa_controls_header     |    |                      |
 *         | |                         |    |                      |
 *         \ |                         |    |                      |
 *           +-------------------------+    |                      |
 *         / | ipa_control_info_entry  |    | hdr.data_offset      |
 *         | | #0                      |    |                      |
 * Control | +-------------------------+    |                      |
 *    info | | ...                     |    |                      |
 * entries | +-------------------------+    |                      |
 *         | | ipa_control_info_entry  |    |             hdr.size |
 *         \ | #hdr.entries - 1        |    |                      |
 *           +-------------------------+    |                      |
 *           | empty space (optional)  |    |                      |
 *           +-------------------------+ <--´  .                   |
 *         / | ...                     |       | entry[n].offset   |
 *    Data | | ...                     |       |                   |
 * section | | info data for entry #n  | <-----´                   |
 *         \ | ...                     |                           |
 *           +-------------------------+                           |
 *           | empty space (optional)  |                           |
 *           +-------------------------+ <-------------------------´
 * ~~~~
 *
 * The packet header is identical to the ControlList packet header.
 *
 * Entries are described by the ipa_control_info_entry structure. They contain
 * the numerical ID and type of the control. The control info data is stored
 * in the data section as described by the following diagram.
 *
 * ~~~~
 *           +-------------------------+       .
 *         / | ...                     |       | entry[n].offset
 *         | +-------------------------+ <-----´
 *    Data | | minimum value (#n)      | \
 * section | +-------------------------+ | Entry #n