转自:http://hi.baidu.com/xdyang1986/blog/item/1681d3d4ef4a63d251da4bd5.html
这个函数的主要功能是根据模块ID寻找硬件模块动态链接库德地址,然后调用load去打开动态链接库并从中获取硬件模块结构体地址。具体的源码如下:
代码@/hardware/libhardware/hardware.c
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int hw_get_module(const char *id, const struct hw_module_t **module)
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120 {
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121 int status;
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122 int i;
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123 const struct hw_module_t *hmi = NULL;
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124 char prop[PATH_MAX];
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125 char path[PATH_MAX];
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135 for (i=0 ; i
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* 47 "ro.product.board",
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* 48 "ro.board.platform",
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* 49 "ro.arch"
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* 50 };
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*这里我们记住这个数组,下面我就将用到它。
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*/
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136 if (i < HAL_VARIANT_KEYS_COUNT) {
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137 if (property_get(variant_keys[i], prop, NULL) == 0) {
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138 continue;
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139 }
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140 snprintf(path, sizeof(path), "%s/%s.%s.so",
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141 HAL_LIBRARY_PATH, id, prop);
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142 } else {
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143 snprintf(path, sizeof(path), "%s/%s.default.so",
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144 HAL_LIBRARY_PATH, id);
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145 }
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146 if (access(path, R_OK)) {
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147 continue;
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148 }
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149
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150 break;
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151 }
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152
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153 status = -ENOENT;
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154 if (i < HAL_VARIANT_KEYS_COUNT+1) {
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155
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157 status = load(id, path, module);
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158 }
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159
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return status;
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161 }
int hw_get_module(const char *id, const struct hw_module_t **module)
120 {
121 int status;
122 int i;
123 const struct hw_module_t *hmi = NULL;
124 char prop[PATH_MAX];
125 char path[PATH_MAX];
/* Loop through the configuration variants looking for a module */
135 for (i=0 ; i
代码@/hardware/libhardware/hardware.c
这个代码其实很简单。load相应库。并把它们的HMI保存到module中
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static int load(const char *id,
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const char *path,
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const struct hw_module_t **pHmi)
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{
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int status;
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void *handle;
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struct hw_module_t *hmi;
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handle = dlopen(path, RTLD_NOW);
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if (handle == NULL) {
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char const *err_str = dlerror();
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LOGE("load: module=%s\n%s", path, err_str?err_str:"unknown");
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status = -EINVAL;
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goto done;
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}
static int load(const char *id,
const char *path,
const struct hw_module_t **pHmi)
{
int status;
void *handle;
struct hw_module_t *hmi;
handle = dlopen(path, RTLD_NOW);//打开相应的库
if (handle == NULL) {
char const *err_str = dlerror();
LOGE("load: module=%s\n%s", path, err_str?err_str:"unknown");
status = -EINVAL;
goto done;
}
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const char *sym = HAL_MODULE_INFO_SYM_AS_STR;
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hmi = (struct hw_module_t *)dlsym(handle, sym);
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if (hmi == NULL) {
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LOGE("load: couldn't find symbol %s", sym);
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status = -EINVAL;
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goto done;
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}
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if (strcmp(id, hmi->id) != 0) {
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LOGE("load: id=%s != hmi->id=%s", id, hmi->id);
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status = -EINVAL;
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goto done;
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}
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hmi->dso = handle;
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status = 0;
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done:
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if (status != 0) {
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hmi = NULL;
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if (handle != NULL) {
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dlclose(handle);
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handle = NULL;
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}
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} else {
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LOGV("loaded HAL id=%s path=%s hmi=%p handle=%p",
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id, path, *pHmi, handle);
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}
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*pHmi = hmi;
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return status;
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}
const char *sym = HAL_MODULE_INFO_SYM_AS_STR;
hmi = (struct hw_module_t *)dlsym(handle, sym);//找到库中的HMI函数的地址(据snownight0102说,HMI不是一个函数,我还不是很清楚,等待解释)
if (hmi == NULL) {
LOGE("load: couldn't find symbol %s", sym);
status = -EINVAL;
goto done;
}
/* Check that the id matches */
if (strcmp(id, hmi->id) != 0) {//只是一个check
LOGE("load: id=%s != hmi->id=%s", id, hmi->id);
status = -EINVAL;
goto done;
}
hmi->dso = handle;
/* success */
status = 0;
done:
if (status != 0) {
hmi = NULL;
if (handle != NULL) {
dlclose(handle);
handle = NULL;
}
} else {
LOGV("loaded HAL id=%s path=%s hmi=%p handle=%p",
id, path, *pHmi, handle);
}
*pHmi = hmi;//把这个返回过去
return status;
}
以上为转载
以下为hardware/libhardware/hardware.c
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#include
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#include
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#include
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#include
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#include
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#include
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#include
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#define LOG_TAG "HAL"
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#include
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#define HAL_LIBRARY_PATH "/system/lib/hw"
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static const char *variant_keys[] = {
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"ro.hardware",
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"ro.product.board",
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"ro.board.platform",
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"ro.arch"
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};
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static const int HAL_VARIANT_KEYS_COUNT =
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(sizeof(variant_keys)/sizeof(variant_keys[0]));
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static int load(const char *id,
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const char *path,
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const struct hw_module_t **pHmi)
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{
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int status;
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void *handle;
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struct hw_module_t *hmi;
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handle = dlopen(path, RTLD_NOW);
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if (handle == NULL) {
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char const *err_str = dlerror();
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LOGE("load: module=%s\n%s", path, err_str?err_str:"unknown");
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status = -EINVAL;
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goto done;
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}
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const char *sym = HAL_MODULE_INFO_SYM_AS_STR;
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hmi = (struct hw_module_t *)dlsym(handle, sym);
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if (hmi == NULL) {
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LOGE("load: couldn't find symbol %s", sym);
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status = -EINVAL;
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goto done;
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}
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if (strcmp(id, hmi->id) != 0) {
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LOGE("load: id=%s != hmi->id=%s", id, hmi->id);
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status = -EINVAL;
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goto done;
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}
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hmi->dso = handle;
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status = 0;
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done:
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if (status != 0) {
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hmi = NULL;
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if (handle != NULL) {
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dlclose(handle);
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handle = NULL;
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}
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} else {
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LOGV("loaded HAL id=%s path=%s hmi=%p handle=%p",
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id, path, *pHmi, handle);
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}
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*pHmi = hmi;
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return status;
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}
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int hw_get_module(const char *id, const struct hw_module_t **module)
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{
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int status;
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int i;
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const struct hw_module_t *hmi = NULL;
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char prop[PATH_MAX];
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char path[PATH_MAX];
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for (i=0 ; i
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if (i < HAL_VARIANT_KEYS_COUNT) {
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if (property_get(variant_keys[i], prop, NULL) == 0) {
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continue;
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}
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snprintf(path, sizeof(path), "%s/%s.%s.so",
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HAL_LIBRARY_PATH, id, prop);
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} else {
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snprintf(path, sizeof(path), "%s/%s.default.so",
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HAL_LIBRARY_PATH, id);
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}
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if (access(path, R_OK)) {
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continue;
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}
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break;
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}
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status = -ENOENT;
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if (i < HAL_VARIANT_KEYS_COUNT+1) {
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status = load(id, path, module);
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}
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return status;
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}
/*
* 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
*
*
*
* 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.
*/
#include
#include
#include
#include
#include
#include
#include
#define LOG_TAG "HAL"
#include
/** Base path of the hal modules */
#define HAL_LIBRARY_PATH "/system/lib/hw"
/**
* There are a set of variant filename for modules. The form of the filename
* is ".variant.so" so for the led module the Dream variants
* of base "ro.product.board", "ro.board.platform" and "ro.arch" would be:
*
* led.trout.so
* led.msm7k.so
* led.ARMV6.so
* led.default.so
*/
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]));
/**
* Load the file defined by the variant and if successful
* return the dlopen handle and the hmi.
* @return 0 = success, !0 = failure.
*/
static int load(const char *id,
const char *path,
const struct hw_module_t **pHmi)
{
int status;
void *handle;
struct hw_module_t *hmi;
/*
* load the symbols resolving undefined symbols before
* dlopen returns. Since RTLD_GLOBAL is not or'd in with
* RTLD_NOW the external symbols will not be global
*/
handle = dlopen(path, RTLD_NOW);
if (handle == NULL) {
char const *err_str = dlerror();
LOGE("load: module=%s\n%s", path, err_str?err_str:"unknown");
status = -EINVAL;
goto done;
}
/* Get the address of the struct hal_module_info. */
const char *sym = HAL_MODULE_INFO_SYM_AS_STR;
hmi = (struct hw_module_t *)dlsym(handle, sym);
if (hmi == NULL) {
LOGE("load: couldn't find symbol %s", sym);
status = -EINVAL;
goto done;
}
/* Check that the id matches */
if (strcmp(id, hmi->id) != 0) {
LOGE("load: id=%s != hmi->id=%s", id, hmi->id);
status = -EINVAL;
goto done;
}
hmi->dso = handle;
/* success */
status = 0;
done:
if (status != 0) {
hmi = NULL;
if (handle != NULL) {
dlclose(handle);
handle = NULL;
}
} else {
LOGV("loaded HAL id=%s path=%s hmi=%p handle=%p",
id, path, *pHmi, handle);
}
*pHmi = hmi;
return status;
}
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
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