android 背光控制 HAL层分析

lights.c
/* * Copyright (C) 2008 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. */#define LOG_TAG "lights"#include <cutils/log.h>#include <stdint.h>#include <string.h>#include <errno.h>#include <fcntl.h>#include <pthread.h>#include <sys/ioctl.h>#include <sys/types.h>#include <hardware/lights.h> static pthread_once_t g_init = PTHREAD_ONCE_INIT;static pthread_mutex_t g_lock = PTHREAD_MUTEX_INITIALIZER;char const *const LCD_FILE = "/sys/class/backlight/pwm-backlight.0/brightness";static int write_int(char const *path, int value){    int fd;    static int already_warned;    already_warned = 0;   // LOGV("write_int: path %s, value %d", path, value);    fd = open(path, O_RDWR);    if (fd >= 0) {        char buffer[20];        int bytes = sprintf(buffer, "%d\n", value);        int amt = write(fd, buffer, bytes);        close(fd);        return amt == -1 ? -errno : 0;    } else {        if (already_warned == 0) {            //LOGE("write_int failed to open %s\n", path);            already_warned = 1;        }        return -errno;    }}static int rgb_to_brightness(struct light_state_t const *state){    int color = state->color & 0x00ffffff;    return ((77*((color>>16) & 0x00ff))        + (150*((color>>8) & 0x00ff)) + (29*(color & 0x00ff))) >> 8;}static int 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;}static int close_lights(struct light_device_t *dev){    ////////LOGV("close_light is called");    if (dev)        free(dev);    return 0;}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);    //LOGV("open_lights: open with %s", name);    if (0 == strcmp(LIGHT_ID_BACKLIGHT, name))        set_light = set_light_backlight;    else        return -EINVAL;    pthread_mutex_init(&g_lock, NULL);    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;}static struct hw_module_methods_t lights_module_methods = {    .open =  open_lights,};const struct hw_module_t HAL_MODULE_INFO_SYM = {    .tag = HARDWARE_MODULE_TAG,    .version_major = 1,    .version_minor = 0,    .id = LIGHTS_HARDWARE_MODULE_ID,    .name = "lights Module",    .author = "Google, Inc.",    .methods = &lights_module_methods,};
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