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
|
<html devsite>
<head>
<title>Implementing the Service</title>
<meta name="project_path" value="/_project.yaml" />
<meta name="book_path" value="/_book.yaml" />
</head>
<body>
<!--
Copyright 2017 The Android Open Source Project
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<p>To prepare for the HAL implementation, you can generate basic configstore
interface code then modify it to meet your needs.</p>
<h2 id=generate-boilerplate>Generating interface code</h2>
<p>To generate boilerplate code for the interface, run <code>hidl-gen</code>.
For example, to generate code for <code>surfaceflinger</code>:</p>
<pre class="devsite-terminal devsite-click-to-copy">
hidl-gen -o hardware/interfaces/configstore/1.0/default \
-Lc++-impl \
-randroid.hardware:hardware/interfaces \
-randroid.hidl:system/libhidl/transport \
android.hardware.config@1.0::ISurfaceFlingerConfigs
</pre>
<p class="note"><strong>Note:</strong> Don't run <code>hidl-gen</code> with
<code>-Landroidbp-impl</code> as this generates <code>Android.bp</code>. The
module must be built with <code>Android.mk</code> to access build flags.</p>
<h2 id=modify-androidmk>Modifying Android.mk</h2>
<p>Next, modify <code>Android.mk</code> file to add implementation file
(<code><modulename>Configs.cpp</code>) to <code>LOCAL_SRC_FILES</code> and
to map build flags into macro definitions. For example, you can modify
<code>surfaceflinger</code> in
<strong><code>hardware/interface/configstore/1.0/default/Android.mk</code></strong>:
</p>
<pre class="devsite-click-to-copy">
LOCAL_SRC_FILES += SurfaceFlingerConfigs.cpp
ifneq ($(NUM_FRAMEBUFFER_SURFACE_BUFFERS),)
LOCAL_CFLAGS += -DNUM_FRAMEBUFFER_SURFACE_BUFFERS=$(NUM_FRAMEBUFFER_SURFACE_BUFFERS)
endif
ifeq ($(TARGET_RUNNING_WITHOUT_SYNC_FRAMEWORK),true)
LOCAL_CFLAGS += -DRUNNING_WITHOUT_SYNC_FRAMEWORK
endif
</pre>
<p>If <code>Android.mk</code> includes several <code>ifeq-endif</code> blocks,
consider moving your code into a new file (i.e., <code>surfaceflinger.mk</code>)
then include that file from <code>Android.mk</code>.</p>
<h2 id=implement-functions>Implementing functions</h2>
<p>To fill the functions to implement the HAL, call back the
<code>_hidl_cb</code> function with different values (conditioned on build
flags). For example, you can fill the functions for <code>surfaceflinger</code>
in <strong><code>hardware/interfaces/configstore/1.0/default/SurfaceFlingerConfigs.cpp</code></strong>:</p>
<pre class="devsite-click-to-copy">
Return<void> SurfaceFlingerConfigs::numFramebufferSurfaceBuffers(
numFramebufferSurfaceBuffers_cb _hidl_cb) {
#if NUM_FRAMEBUFFER_SURFACE_BUFFERS 2
_hidl_cb(NumBuffers.TWO);
#else if NUM_FRAMEBUFFER_SURFACE_BUFFERS 3
_hidl_cb(NumBuffers.THREE);
#else
_hidl_cb(NumBuffers.USE_DEFAULT);
#endif
}
Return<void> SurfaceFlingerConfigs::runWithoutSyncFramework(
runWithoutSyncFramework_cb _hidl_cb) {
#ifdef RUNNING_WITHOUT_SYNC_FRAMEWORK
_hidl_cb({true /* specified */, true /* value */});
#else
// when macro not defined, we can give any value to the second argument.
// It will simply be ignored in the framework side.
_hidl_cb({false /* specified */, false /* value */});
#endif
}
</pre>
<p>Ensure the implementation does not contain a function named
<code>HIDL_FETCH_<interface name></code> (e.g.,
<code>HIDL_FETCH_ISurfaceFlingerConfigs</code>). This function is needed for
HIDL passthrough mode, which is unused (and prohibited) by
<code>configstore</code>. ConfigStore must always run in binderized mode.</p>
<h2 id=register-service>Registering as a service</h2>
<p>Finally, register all interface implementations to the
<code>configstore</code> service. For example, you can register
<code>surfaceflinger</code> implementations in
<strong><code>hardware/interfaces/configstore/1.0/default/service.cpp</code></strong>:
</p>
<pre class="devsite-click-to-copy">
configureRpcThreadpool(maxThreads, true);
sp<ISurfaceFlingerConfigs> surfaceFlingerConfigs = new SurfaceFlingerConfigs;
status_t status = surfaceFlingerConfigs->registerAsService();
sp<IBluetoothConfigs> bluetoothConfigs = new BluetoothConfigs;
status = bluetoothConfigs->registerAsService();
// register more interfaces here
joinRpcThreadpool();
</pre>
<h2 id=bootstrapping>Ensuring early access</h2>
<p>To ensure a framework module can get early access the HAL service, the config
HAL service should start as early as possible, just after
<code>hwservicemanager</code> is ready. As the config HAL service does not read
external files, it is expected to be ready quickly after it is launched.</p>
</body>
</html>
|
