我正在学习Android源代码。而且我想知道较低级别的函数是如何从应用程序调用的。
在学习这方面的同时,现在我正在努力理解我在下面给出的一个文件:
static int open_lights(const struct hw_module_t* module, char const* name,
struct hw_device_t** device)
{
int (*set_light)(struct light_device_t* dev,
struct light_state_t const* state);
if (0 == strcmp(LIGHT_ID_BACKLIGHT, name)) {
set_light = set_light_backlight;
}
else if (0 == strcmp(LIGHT_ID_KEYBOARD, name)) {
set_light = set_light_keyboard;
}
else if (0 == strcmp(LIGHT_ID_BUTTONS, name)) {
set_light = set_light_buttons;
}
else if (0 == strcmp(LIGHT_ID_BATTERY, name)) {
set_light = set_light_battery;
}
else if (0 == strcmp(LIGHT_ID_NOTIFICATIONS, name)) {
set_light = set_light_notification;
}
else if (0 == strcmp(LIGHT_ID_ATTENTION, name)) {
set_light = set_light_attention;
}
else {
return -EINVAL;
}
pthread_once(&g_init, init_globals);
struct light_device_t *dev = malloc(sizeof(struct light_device_t));
memset(dev, 0, sizeof(*dev));
dev->common.tag = HARDWARE_DEVICE_TAG;
dev->common.version = 0;
dev->common.module = (struct hw_module_t*)module;
dev->common.close = (int (*)(struct hw_device_t*))close_lights;
dev->set_light = set_light;
*device = (struct hw_device_t*)dev;
return 0;
}
set_light_backlight(struct light_device_t* dev,
struct light_state_t const* state)
{
int err = 0;
int brightness = rgb_to_brightness(state);
pthread_mutex_lock(&g_lock);
err = write_int(LCD_FILE, brightness);
pthread_mutex_unlock(&g_lock);
return err;
}
我的问题是:
- 这句话的含义是什么
int (*set_light)(struct light_device_t* dev, struct light_state_t const* state);
? - 我们只是分配
set_light_backlight
给set_light
. 那么如何set_light_backlight(struct light_device_t* dev, struct light_state_t const* state)
调用函数呢?