2 * Copyright (C) 2008 The Android Open Source Project
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
17 #include <hardware/hardware.h>
19 #include <cutils/properties.h>
28 #include <utils/Log.h>
30 /** Base path of the hal modules */
31 #define HAL_LIBRARY_PATH "/system/lib/hw"
34 * There are a set of variant filename for modules. The form of the filename
35 * is "<MODULE_ID>.variant.so" so for the led module the Dream variants
36 * of base "ro.product.board", "ro.board.platform" and "ro.arch" would be:
44 static const char *variant_keys[] = {
45 "ro.hardware", /* This goes first so that it can pick up a different
46 file on the emulator. */
52 static const int HAL_VARIANT_KEYS_COUNT =
53 (sizeof(variant_keys)/sizeof(variant_keys[0]));
56 * Load the file defined by the variant and if successful
57 * return the dlopen handle and the hmi.
58 * @return 0 = success, !0 = failure.
60 static int load(const char *id,
62 const struct hw_module_t **pHmi)
66 struct hw_module_t *hmi;
69 * load the symbols resolving undefined symbols before
70 * dlopen returns. Since RTLD_GLOBAL is not or'd in with
71 * RTLD_NOW the external symbols will not be global
73 handle = dlopen(path, RTLD_NOW);
75 char const *err_str = dlerror();
76 LOGE("load: module=%s\n%s", path, err_str?err_str:"unknown");
81 /* Get the address of the struct hal_module_info. */
82 const char *sym = HAL_MODULE_INFO_SYM_AS_STR;
83 hmi = (struct hw_module_t *)dlsym(handle, sym);
85 LOGE("load: couldn't find symbol %s", sym);
90 /* Check that the id matches */
91 if (strcmp(id, hmi->id) != 0) {
92 LOGE("load: id=%s != hmi->id=%s", id, hmi->id);
105 if (handle != NULL) {
110 LOGV("loaded HAL id=%s path=%s hmi=%p handle=%p",
111 id, path, *pHmi, handle);
119 int hw_get_module(const char *id, const struct hw_module_t **module)
123 const struct hw_module_t *hmi = NULL;
128 * Here we rely on the fact that calling dlopen multiple times on
129 * the same .so will simply increment a refcount (and not load
130 * a new copy of the library).
131 * We also assume that dlopen() is thread-safe.
134 /* Loop through the configuration variants looking for a module */
135 for (i=0 ; i<HAL_VARIANT_KEYS_COUNT+1 ; i++) {
136 if (i < HAL_VARIANT_KEYS_COUNT) {
137 if (property_get(variant_keys[i], prop, NULL) == 0) {
140 snprintf(path, sizeof(path), "%s/%s.%s.so",
141 HAL_LIBRARY_PATH, id, prop);
143 snprintf(path, sizeof(path), "%s/%s.default.so",
144 HAL_LIBRARY_PATH, id);
146 if (access(path, R_OK)) {
149 /* we found a library matching this id/variant */
154 if (i < HAL_VARIANT_KEYS_COUNT+1) {
155 /* load the module, if this fails, we're doomed, and we should not try
156 * to load a different variant. */
157 status = load(id, path, module);