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#include <stdlib.h>
27
28#define LOG_TAG "HAL"
29#ifdef ANDROID
30#include <utils/Log.h>
31#else
32#include <stdio.h>
33#include <unistd.h>
34#include <log/log.h>
35#endif
36
37#if defined(__LP64__)
38#define _64 "64"
39#else
40#define _64 ""
41#endif
42
43/** Base path of the hal modules */
44#ifndef HAL_LIBRARY_PATH1
45#define HAL_LIBRARY_PATH1 "/system/lib" _64 "/hw"
46#endif
47#ifndef HAL_LIBRARY_PATH2
48#define HAL_LIBRARY_PATH2 "/vendor/lib" _64 "/hw"
49#endif
50
51/**
52 * There are a set of variant filename for modules. The form of the filename
53 * is "<MODULE_ID>.variant.so" so for the led module the Dream variants
54 * of base "ro.product.board", "ro.board.platform" and "ro.arch" would be:
55 *
56 * led.trout.so
57 * led.msm7k.so
58 * led.ARMV6.so
59 * led.default.so
60 */
61
62static const char *variant_keys[] = {
63    "ro.hardware",  /* This goes first so that it can pick up a different
64                       file on the emulator. */
65    "ro.product.board",
66    "ro.board.platform",
67    "ro.arch"
68};
69
70static const int HAL_VARIANT_KEYS_COUNT =
71    (sizeof(variant_keys)/sizeof(variant_keys[0]));
72
73/**
74 * Load the file defined by the variant and if successful
75 * return the dlopen handle and the hmi.
76 * @return 0 = success, !0 = failure.
77 */
78static int load(const char *id,
79        const char *path,
80        const struct hw_module_t **pHmi)
81{
82    int status;
83    void *handle;
84    struct hw_module_t *hmi;
85
86    /*
87     * load the symbols resolving undefined symbols before
88     * dlopen returns. Since RTLD_GLOBAL is not or'd in with
89     * RTLD_NOW the external symbols will not be global
90     */
91    handle = dlopen(path, RTLD_NOW);
92    if (handle == NULL) {
93        char const *err_str = dlerror();
94        ALOGE("load: module=%s\n%s", path, err_str?err_str:"unknown");
95        status = -EINVAL;
96        goto done;
97    }
98
99    /* Get the address of the struct hal_module_info. */
100    const char *sym = HAL_MODULE_INFO_SYM_AS_STR;
101    hmi = (struct hw_module_t *)dlsym(handle, sym);
102    if (hmi == NULL) {
103        ALOGE("load: couldn't find symbol %s", sym);
104        status = -EINVAL;
105        goto done;
106    }
107
108    /* Check that the id matches */
109    if (strcmp(id, hmi->id) != 0) {
110        ALOGE("load: id=%s != hmi->id=%s", id, hmi->id);
111        status = -EINVAL;
112        goto done;
113    }
114
115    hmi->dso = handle;
116
117    /* success */
118    status = 0;
119
120    done:
121    if (status != 0) {
122        hmi = NULL;
123        if (handle != NULL) {
124            dlclose(handle);
125            handle = NULL;
126        }
127    } else {
128        ALOGV("loaded HAL id=%s path=%s hmi=%p handle=%p",
129                id, path, *pHmi, handle);
130    }
131
132    *pHmi = hmi;
133
134    return status;
135}
136
137/*
138 * Check if a HAL with given name and subname exists, if so return 0, otherwise
139 * otherwise return negative.  On success path will contain the path to the HAL.
140 */
141static int hw_module_exists(char *path, size_t path_len, const char *name,
142                            const char *subname)
143{
144    char *hal_library_path = getenv("HAL_LIBRARY_PATH");
145    if (hal_library_path) {
146        snprintf(path, path_len, "%s/%s.%s.so",
147                 hal_library_path, name, subname);
148        if (access(path, R_OK) == 0)
149            return 0;
150    }
151
152    snprintf(path, path_len, "%s/%s.%s.so",
153             HAL_LIBRARY_PATH2, name, subname);
154    if (access(path, R_OK) == 0)
155        return 0;
156
157    snprintf(path, path_len, "%s/%s.%s.so",
158             HAL_LIBRARY_PATH1, name, subname);
159    if (access(path, R_OK) == 0)
160        return 0;
161
162    return -ENOENT;
163}
164
165int hw_get_module_by_class(const char *class_id, const char *inst,
166                           const struct hw_module_t **module)
167{
168    int i;
169    char prop[PATH_MAX];
170    char path[PATH_MAX];
171    char name[PATH_MAX];
172    char prop_name[PATH_MAX];
173
174    if (inst)
175        snprintf(name, PATH_MAX, "%s.%s", class_id, inst);
176    else
177        strlcpy(name, class_id, PATH_MAX);
178
179    /*
180     * Here we rely on the fact that calling dlopen multiple times on
181     * the same .so will simply increment a refcount (and not load
182     * a new copy of the library).
183     * We also assume that dlopen() is thread-safe.
184     */
185
186    /* First try a property specific to the class and possibly instance */
187    snprintf(prop_name, sizeof(prop_name), "ro.hardware.%s", name);
188    if (property_get(prop_name, prop, NULL) > 0) {
189        if (hw_module_exists(path, sizeof(path), name, prop) == 0) {
190            goto found;
191        }
192    }
193
194    /* Loop through the configuration variants looking for a module */
195    for (i=0 ; i<HAL_VARIANT_KEYS_COUNT; i++) {
196        if (property_get(variant_keys[i], prop, NULL) == 0) {
197            continue;
198        }
199        if (hw_module_exists(path, sizeof(path), name, prop) == 0) {
200            goto found;
201        }
202    }
203
204    /* Nothing found, try the default */
205    if (hw_module_exists(path, sizeof(path), name, "default") == 0) {
206        goto found;
207    }
208
209    return -ENOENT;
210
211found:
212    /* load the module, if this fails, we're doomed, and we should not try
213     * to load a different variant. */
214    return load(class_id, path, module);
215}
216
217int hw_get_module(const char *id, const struct hw_module_t **module)
218{
219    return hw_get_module_by_class(id, NULL, module);
220}
221