1 /*
2 * Copyright (C) 2008 The Android Open Source Project
3 *
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
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
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.
15 */
16
17 #include <hardware/hardware.h>
18
19 #include <cutils/properties.h>
20
21 #include <dlfcn.h>
22 #include <string.h>
23 #include <pthread.h>
24 #include <errno.h>
25 #include <limits.h>
26
27 #define LOG_TAG "HAL"
28 #include <utils/Log.h>
29
30 /** Base path of the hal modules */
31 #define HAL_LIBRARY_PATH1 "/system/lib/hw"
32 #define HAL_LIBRARY_PATH2 "/vendor/lib/hw"
33
34 /**
35 * There are a set of variant filename for modules. The form of the filename
36 * is "<MODULE_ID>.variant.so" so for the led module the Dream variants
37 * of base "ro.product.board", "ro.board.platform" and "ro.arch" would be:
38 *
39 * led.trout.so
40 * led.msm7k.so
41 * led.ARMV6.so
42 * led.default.so
43 */
44
45 static const char *variant_keys[] = {
46 "ro.hardware", /* This goes first so that it can pick up a different
47 file on the emulator. */
48 "ro.product.board",
49 "ro.board.platform",
50 "ro.arch"
51 };
52
53 static const int HAL_VARIANT_KEYS_COUNT =
54 (sizeof(variant_keys)/sizeof(variant_keys[0]));
55
56 /**
57 * Load the file defined by the variant and if successful
58 * return the dlopen handle and the hmi.
59 * @return 0 = success, !0 = failure.
60 */
load(const char * id,const char * path,const struct hw_module_t ** pHmi)61 static int load(const char *id,
62 const char *path,
63 const struct hw_module_t **pHmi)
64 {
65 int status;
66 void *handle;
67 struct hw_module_t *hmi;
68
69 /*
70 * load the symbols resolving undefined symbols before
71 * dlopen returns. Since RTLD_GLOBAL is not or'd in with
72 * RTLD_NOW the external symbols will not be global
73 */
74 handle = dlopen(path, RTLD_NOW);
75 if (handle == NULL) {
76 char const *err_str = dlerror();
77 ALOGE("load: module=%s\n%s", path, err_str?err_str:"unknown");
78 status = -EINVAL;
79 goto done;
80 }
81
82 /* Get the address of the struct hal_module_info. */
83 const char *sym = HAL_MODULE_INFO_SYM_AS_STR;
84 hmi = (struct hw_module_t *)dlsym(handle, sym);
85 if (hmi == NULL) {
86 ALOGE("load: couldn't find symbol %s", sym);
87 status = -EINVAL;
88 goto done;
89 }
90
91 /* Check that the id matches */
92 if (strcmp(id, hmi->id) != 0) {
93 ALOGE("load: id=%s != hmi->id=%s", id, hmi->id);
94 status = -EINVAL;
95 goto done;
96 }
97
98 hmi->dso = handle;
99
100 /* success */
101 status = 0;
102
103 done:
104 if (status != 0) {
105 hmi = NULL;
106 if (handle != NULL) {
107 dlclose(handle);
108 handle = NULL;
109 }
110 } else {
111 ALOGV("loaded HAL id=%s path=%s hmi=%p handle=%p",
112 id, path, *pHmi, handle);
113 }
114
115 *pHmi = hmi;
116
117 return status;
118 }
119
hw_get_module_by_class(const char * class_id,const char * inst,const struct hw_module_t ** module)120 int hw_get_module_by_class(const char *class_id, const char *inst,
121 const struct hw_module_t **module)
122 {
123 int status;
124 int i;
125 const struct hw_module_t *hmi = NULL;
126 char prop[PATH_MAX];
127 char path[PATH_MAX];
128 char name[PATH_MAX];
129
130 if (inst)
131 snprintf(name, PATH_MAX, "%s.%s", class_id, inst);
132 else
133 strlcpy(name, class_id, PATH_MAX);
134
135 /*
136 * Here we rely on the fact that calling dlopen multiple times on
137 * the same .so will simply increment a refcount (and not load
138 * a new copy of the library).
139 * We also assume that dlopen() is thread-safe.
140 */
141
142 /* Loop through the configuration variants looking for a module */
143 for (i=0 ; i<HAL_VARIANT_KEYS_COUNT+1 ; i++) {
144 if (i < HAL_VARIANT_KEYS_COUNT) {
145 if (property_get(variant_keys[i], prop, NULL) == 0) {
146 continue;
147 }
148 snprintf(path, sizeof(path), "%s/%s.%s.so",
149 HAL_LIBRARY_PATH2, name, prop);
150 if (access(path, R_OK) == 0) break;
151
152 snprintf(path, sizeof(path), "%s/%s.%s.so",
153 HAL_LIBRARY_PATH1, name, prop);
154 if (access(path, R_OK) == 0) break;
155 } else {
156 snprintf(path, sizeof(path), "%s/%s.default.so",
157 HAL_LIBRARY_PATH1, name);
158 if (access(path, R_OK) == 0) break;
159 }
160 }
161
162 status = -ENOENT;
163 if (i < HAL_VARIANT_KEYS_COUNT+1) {
164 /* load the module, if this fails, we're doomed, and we should not try
165 * to load a different variant. */
166 status = load(class_id, path, module);
167 }
168
169 return status;
170 }
171
hw_get_module(const char * id,const struct hw_module_t ** module)172 int hw_get_module(const char *id, const struct hw_module_t **module)
173 {
174 return hw_get_module_by_class(id, NULL, module);
175 }
176