飞翼零式高达改mg:ADROID 2.1 架构解析 3 亮度设置(二)
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3.3 硬件调用
3.3.1获取硬件
文件:frameworks/base/services/jni/com_android_server_HardwareService.cpp
enum {
LIGHT_INDEX_BACKLIGHT = 0,
LIGHT_INDEX_KEYBOARD = 1,
LIGHT_INDEX_BUTTONS = 2,
LIGHT_INDEX_BATTERY = 3,
LIGHT_INDEX_NOTIFICATIONS = 4,
LIGHT_INDEX_ATTENTION = 5,
LIGHT_COUNT
};
#define LIGHTS_HARDWARE_MODULE_ID "lights"
static jint init_native(JNIEnv *env, jobject clazz)
{
int err;
hw_module_t* module;
Devices* devices;
devices = (Devices*)malloc(sizeof(Devices));
err = hw_get_module(LIGHTS_HARDWARE_MODULE_ID, (hw_module_t const**)&module);
if (err == 0) {
devices->lights[LIGHT_INDEX_BACKLIGHT]
= get_device(module, LIGHT_ID_BACKLIGHT);
devices->lights[LIGHT_INDEX_KEYBOARD]
= get_device(module, LIGHT_ID_KEYBOARD);
devices->lights[LIGHT_INDEX_BUTTONS]
= get_device(module, LIGHT_ID_BUTTONS);
devices->lights[LIGHT_INDEX_BATTERY]
= get_device(module, LIGHT_ID_BATTERY);
devices->lights[LIGHT_INDEX_NOTIFICATIONS]
= get_device(module, LIGHT_ID_NOTIFICATIONS);
devices->lights[LIGHT_INDEX_ATTENTION]
= get_device(module, LIGHT_ID_ATTENTION);
} else {
memset(devices, 0, sizeof(Devices));
}
return (jint)devices;
}
用hw_get_module获取ID为LIGHTS_HARDWARE_MODULE_ID的硬件模块,该模块含有6个不同类型的亮度控制。
hw_get_module 的实现原理,如下:
文件:hardware/libhardware/Hardware.c
#define HAL_LIBRARY_PATH "/system/lib/hw"
static const char *variant_keys[] = {
"ro.hardware", /* This goes first so that it can pick up a different
file on the emulator. */
"ro.product.board",
"ro.board.platform",
"ro.arch"
};
static const int HAL_VARIANT_KEYS_COUNT =
(sizeof(variant_keys)/sizeof(variant_keys[0]));
int hw_get_module(const char *id, const struct hw_module_t **module)
{
int status;
int i;
const struct hw_module_t *hmi = NULL;
char prop[PATH_MAX];
char path[PATH_MAX];
/*
* Here we rely on the fact that calling dlopen multiple times on
* the same .so will simply increment a refcount (and not load
* a new copy of the library).
* We also assume that dlopen() is thread-safe.
*/
/* Loop through the configuration variants looking for a module */
for (i=0 ; i if (i < HAL_VARIANT_KEYS_COUNT) { if (property_get(variant_keys[i], prop, NULL) == 0) { continue; } snprintf(path, sizeof(path), "%s/%s.%s.so", HAL_LIBRARY_PATH, id, prop); } else { snprintf(path, sizeof(path), "%s/%s.default.so", HAL_LIBRARY_PATH, id); } if (access(path, R_OK)) { continue; } /* we found a library matching this id/variant */ break; } status = -ENOENT; if (i < HAL_VARIANT_KEYS_COUNT+1) { /* load the module, if this fails, we're doomed, and we should not try * to load a different variant. */ status = load(id, path, module); } return status; } property_get(variant_keys[i], prop, NULL) 会按如下顺序去获取如下变量所对应的值,然后返回给prop: "ro.hardware", /* This goes first so that it can pick up a different file on the emulator. */ "ro.product.board", "ro.board.platform", "ro.arch" 它们对应的变量为: "ro.product.board=$TARGET_BOOTLOADER_BOARD_NAME" "ro.board.platform=$TARGET_BOARD_PLATFORM" 如vendor/htc/dream-open/BoardConfig.mk里定义的TARGET_BOARD_PLATFORM := msm7k,则prop返回” msm7k ”,所以path = /system/lib/hw/lights. msm7k.so,也就是说要获取的硬件模块为lights. msm7k.so。