lights.c

/*
 * Copyright (C) 2012 Stefan Seidel
 *
 * 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 <sys/types.h>
#include <dirent.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <pthread.h>

#include <hardware/lights.h>
#include <cutils/properties.h>

/******************************************************************************/

static pthread_once_t g_init = PTHREAD_ONCE_INIT;
static pthread_mutex_t g_lock = PTHREAD_MUTEX_INITIALIZER;
static int max_brightness = 255;
static char brightness_file[PROPERTY_VALUE_MAX] = { '\0' };

char const*const LLP_BRIGHTNESS_FILE     = "backlight.brightness_file";
char const*const LLP_MAX_BRIGHTNESS_FILE = "backlight.max_brightness_file";
char const*const LLP_MAX_BRIGHTNESS      = "backlight.max_brightness";

void init_globals(void)
{
    pthread_mutex_init(&g_lock, NULL);
}

static int write_int(char* path, int value)
{
    int fd;
    static int already_warned = 0;

    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) {
            ALOGE("write_int failed to open %s\n", path);
            already_warned = 1;
        }
        return -errno;
    }
}

static int read_int(char* path)
{
    int fd;

    fd = open(path, O_RDONLY);
    if (fd >= 0) {
        char buffer[20];
        int amt = read(fd, buffer, 20);
        close(fd);
        if (amt <= 0) return -errno;
        int ret = -1;
        amt = sscanf(buffer, "%d", &ret);
        return amt == -1 ? -errno : ret;
    }
    return -errno;
}

static int rgb_to_brightness16(struct light_state_t const* state)
{
    int color = state->color & 0x00ffffff;
    return ((77*((color>>16)&0x00ff)) + (150*((color>>8)&0x00ff)) + (29*(color&0x00ff)));
}

static int set_light_backlight(struct light_device_t* dev __attribute__ ((__unused__)), struct light_state_t const* state)
{
    int err = 0;
    int brightness = rgb_to_brightness16(state);

    if (max_brightness < 65536)
        brightness = brightness / (65536 / (max_brightness + 1));
    else
        brightness = brightness * (max_brightness / 65536);

    pthread_mutex_lock(&g_lock);
    err = write_int(brightness_file, (brightness));
    pthread_mutex_unlock(&g_lock);

    return err;
}

static int close_lights(struct light_device_t *dev)
{
    free(dev);
    return 0;
}

static int check_backlight_file(char const* name, char* path)
{
    int ret;
    if (access(name, F_OK)) {
        ret = 0;
    } else {
        ALOGD("Detect %s", name);
        strcpy(path, name);
        ret = 1; // found
    }
    return ret;
}

static int find_backlight_file(char const* file, char* path)
{
    int ret = 0;
    size_t i;
    DIR* dir;
    char name[PATH_MAX];
    const char* dirname = "/sys/class/backlight";
    const char* dirs[] = {
        "eeepc",
        "intel_backlight",
        "thinkpad_screen",
        "acpi_video0",
    };

    // Check some known dirs
    for (i = 0; i < sizeof(dirs) / sizeof(const char*); ++i) {
        snprintf(name, PATH_MAX, "%s/%s/%s", dirname, dirs[i], file);
        if (check_backlight_file(name, path)) {
            ALOGV("Using device %s", name);
            return 1;
        }
    }

    if ((dir = opendir(dirname))) {
        struct dirent* de;
        while ((de = readdir(dir))) {
            if (de->d_name[0] != '.') {
                snprintf(name, PATH_MAX, "%s/%s/%s", dirname, de->d_name, file);
                if ((ret = check_backlight_file(name, path))) {
                    break;
                }
            }
        }
        closedir(dir);
    }
    return ret;
}

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;
        char max_b_file[PROPERTY_VALUE_MAX] = { '\0' };
        if (property_get(LLP_MAX_BRIGHTNESS, max_b_file, NULL)) {
            if (!sscanf(max_b_file, "%d", &max_brightness)) {
                ALOGE("%s system property is set to '%s', this could not be parsed as an integer!", LLP_MAX_BRIGHTNESS, max_b_file);
                return -EINVAL;
            }
        } else {
            if (property_get(LLP_MAX_BRIGHTNESS_FILE, max_b_file, NULL) ||
                    find_backlight_file("max_brightness", max_b_file)) {
                max_brightness = read_int(max_b_file);
            } else {
                ALOGE("Unable to detect max_brightness. Try to set %s", LLP_MAX_BRIGHTNESS_FILE);
                return -EINVAL;
            }
        }
        ALOGV("Read max display brightness of %d", max_brightness);
        if (max_brightness < 1) {
            max_brightness = 255;
        }
        if (!property_get(LLP_BRIGHTNESS_FILE, brightness_file, NULL) &&
                !find_backlight_file("brightness", brightness_file)) {
            ALOGE("%s system property not set", LLP_BRIGHTNESS_FILE);
            return -EINVAL;
        }
    } 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.close = (int (*)(struct hw_device_t*))close_lights;
    dev->common.module = (struct hw_module_t*)module;
    dev->common.version = 0;
    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,
};

struct hw_module_t HAL_MODULE_INFO_SYM = {
    .tag = HARDWARE_MODULE_TAG,
    .version_major = 1,
    .version_minor = 0,
    .id = LIGHTS_HARDWARE_MODULE_ID,
    .name = "Generic sysfs liblights implementation",
    .author = "Stefan Seidel",
    .methods = &lights_module_methods,
};