編譯HAL層生成lib.so檔案
本文以編譯LCD背光的庫檔案為例,生成的庫檔案為 lights.mini6410.so.
原始檔的目錄為:Android-2.3.4/device/samsung/crespo/liblight/ light.c Android.mk
light.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, };
char const *const LCD_FILE = "/sys/class/backlight/pwm-backlight.0/brightness"; 是核心驅動載入後生成的節點檔案,應用層傳遞brightness引數到節點,控制亮度。
Android.mk
# 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. #ifneq ($(filter crespo crespo4g,$(TARGET_DEVICE)),) LOCAL_PATH:= $(call my-dir) # HAL module implemenation, not prelinked and stored in # hw/<COPYPIX_HARDWARE_MODULE_ID>.<ro.board.platform>.so include $(CLEAR_VARS) LOCAL_SRC_FILES := lights.c LOCAL_PRELINK_MODULE := false LOCAL_MODULE_PATH := $(TARGET_OUT_SHARED_LIBRARIES)/hw LOCAL_SHARED_LIBRARIES := liblog LOCAL_MODULE := lights.$(TARGET_BOARD_PLATFORM) #LOCAL_MODULE := lights.default #LOCAL_MODULE_TAGS := optional LOCAL_MODULE_TAGS := eng include $(BUILD_SHARED_LIBRARY) #endif
編譯的時候遇到的問題:
1、編譯之後沒有生成lights.mini6410.so,原因是Android.mk中的這一句沒有執行時判斷不通過:ifneq ($(filter crespo crespo4g,$(TARGET_DEVICE)),),將其遮蔽就可以生成所需的檔案了。
2、在out/target/product/mini6410/system/lib/目錄下沒有產生 lights.mini6410.so檔案, 是由於LOCAL_MODULE_TAGS的值得原因, 當LOCAL_MODULE_TAGS := optional時,編譯生成的庫檔案到了out/target/product/mini6410/symbols/system/lib/目錄下;當LOCAL_MODULE_TAGS := eng 時,編譯生成的庫檔案到了out/target/product/mini6410/system/lib/目錄下,android2.3版本是這樣,也許高階的版本不是這樣,有待驗證。
Android.mk中的LOCAL_MODULE的名字的取法也是有講究的,應該是對應的 xxx.xxx,前一個給功能,後一個為板子的名稱或者default ,名字例如mini6410,,和out/target/product/mini6410一致。