hardware.c revision 8232b50d981ce9c584fc1a4af82dae5e70e6ce52 
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_PATH "/system/lib/hw"
32
33/**
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:
37 *
38 * led.trout.so
39 * led.msm7k.so
40 * led.ARMV6.so
41 * led.default.so
42 */
43
44#define HAL_DEFAULT_VARIANT     "default"
45static 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#define HAL_VARIANT_KEYS_COUNT  (sizeof(variant_keys)/sizeof(variant_keys[0]))
53
54/**
55 * Load the file defined by the variant and if succesfull
56 * return the dlopen handle and the hmi.
57 * @return 0 = success, !0 = failure.
58 */
59static int load(const char *id,
60                const char *variant,
61                const struct hw_module_t **pHmi)
62{
63    int status;
64    void *handle;
65    const struct hw_module_t *hmi;
66    char path[PATH_MAX];
67
68    /* Construct the path. */
69    snprintf(path, sizeof(path), "%s/%s.%s.so", HAL_LIBRARY_PATH, id, variant);
70
71    LOGV("load: E id=%s path=%s", id, path);
72
73    /*
74     * load the symbols resolving undefined symbols before
75     * dlopen returns. Since RTLD_GLOBAL is not or'd in with
76     * RTLD_NOW the external symbols will not be global
77     */
78    handle = dlopen(path, RTLD_NOW);
79    if (handle == NULL) {
80        char const *err_str = dlerror();
81        LOGW("load: module=%s error=%s", path, err_str);
82        status = -EINVAL;
83        goto done;
84    }
85
86    /* Get the address of the struct hal_module_info. */
87    const char *sym = HAL_MODULE_INFO_SYM_AS_STR;
88    hmi = (const struct hw_module_t *)dlsym(handle, sym);
89    if (hmi == NULL) {
90        char const *err_str = dlerror();
91        LOGE("load: couldn't find symbol %s", sym);
92        status = -EINVAL;
93        goto done;
94    }
95
96    /* Check that the id matches */
97    if (strcmp(id, hmi->id) != 0) {
98        LOGE("load: id=%s != hmi->id=%s", id, hmi->id);
99        status = -EINVAL;
100        goto done;
101    }
102
103    /* success */
104    status = 0;
105
106done:
107    if (status != 0) {
108        hmi = NULL;
109        if (handle != NULL) {
110            dlclose(handle);
111            handle = NULL;
112        }
113    }
114
115    *pHmi = hmi;
116
117    LOGV("load: X id=%s path=%s hmi=%p handle=%p status=%d",
118         id, path, *pHmi, handle, status);
119    return status;
120}
121
122int hw_get_module(const char *id, const struct hw_module_t **module)
123{
124    int status;
125    int i;
126    const struct hw_module_t *hmi = NULL;
127    char prop[PATH_MAX];
128
129    /*
130     * Here we rely on the fact that calling dlopen multiple times on
131     * the same .so will simply increment a refcount (and not load
132     * a new copy of the library).
133     * We also assume that dlopen() is thread-safe.
134     */
135
136    LOGV("hal_module_info_get: Load module id=%s", id);
137
138    status = -EINVAL;
139
140    /* Loop through the configuration variants looking for a module */
141    for (i = 0; (status != 0) && (i < HAL_VARIANT_KEYS_COUNT); i++) {
142        if (property_get(variant_keys[i], prop, NULL) == 0) {
143            continue;
144        }
145        status = load(id, prop, &hmi);
146    }
147
148    /* Try default */
149    if (status != 0) {
150        status = load(id, HAL_DEFAULT_VARIANT, &hmi);
151    }
152
153    *module = hmi;
154    LOGV("hal_module_info_get: X id=%s hmi=%p status=%d", id, hmi, status);
155
156    return status;
157}
158