Baseline of hwcplus package taken from KitKat AOSP.

third_party/hwcplus/src/hardware.c

+/*
+ * 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
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * 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 <hardware/hardware.h>
+
+#include <cutils/properties.h>
+
+#include <dlfcn.h>
+#include <string.h>
+#include <pthread.h>
+#include <errno.h>
+#include <limits.h>
+
+#define LOG_TAG "HAL"
+#include <utils/Log.h>
+
+/** Base path of the hal modules */
+#if defined(__LP64__)
+#define HAL_LIBRARY_PATH1 "/system/lib64/hw"
+#define HAL_LIBRARY_PATH2 "/vendor/lib64/hw"
+#else
+#define HAL_LIBRARY_PATH1 "/system/lib/hw"
+#define HAL_LIBRARY_PATH2 "/vendor/lib/hw"
+#endif
+
+/**
+ * There are a set of variant filename for modules. The form of the filename
+ * is "<MODULE_ID>.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();
+        ALOGE("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) {
+        ALOGE("load: couldn't find symbol %s", sym);
+        status = -EINVAL;
+        goto done;
+    }
+
+    /* Check that the id matches */
+    if (strcmp(id, hmi->id) != 0) {
+        ALOGE("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 {
+        ALOGV("loaded HAL id=%s path=%s hmi=%p handle=%p",
+                id, path, *pHmi, handle);
+    }
+
+    *pHmi = hmi;
+
+    return status;
+}
+
+/*
+ * Check if a HAL with given name and subname exists, if so return 0, otherwise
+ * otherwise return negative.  On success path will contain the path to the HAL.
+ */
+static int hw_module_exists(char *path, size_t path_len, const char *name,
+                            const char *subname)
+{
+    snprintf(path, path_len, "%s/%s.%s.so",
+             HAL_LIBRARY_PATH2, name, subname);
+    if (access(path, R_OK) == 0)
+        return 0;
+
+    snprintf(path, path_len, "%s/%s.%s.so",
+             HAL_LIBRARY_PATH1, name, subname);
+    if (access(path, R_OK) == 0)
+        return 0;
+
+    return -ENOENT;
+}
+
+int hw_get_module_by_class(const char *class_id, const char *inst,
+                           const struct hw_module_t **module)
+{
+    int i;
+    char prop[PATH_MAX];
+    char path[PATH_MAX];
+    char name[PATH_MAX];
+    char prop_name[PATH_MAX];
+
+    if (inst)
+        snprintf(name, PATH_MAX, "%s.%s", class_id, inst);
+    else
+        strlcpy(name, class_id, 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.
+     */
+
+    /* First try a property specific to the class and possibly instance */
+    snprintf(prop_name, sizeof(prop_name), "ro.hardware.%s", name);
+    if (property_get(prop_name, prop, NULL) > 0) {
+        if (hw_module_exists(path, sizeof(path), name, prop) == 0) {
+            goto found;
+        }
+    }
+
+    /* Loop through the configuration variants looking for a module */
+    for (i=0 ; i<HAL_VARIANT_KEYS_COUNT; i++) {
+        if (property_get(variant_keys[i], prop, NULL) == 0) {
+            continue;
+        }
+        if (hw_module_exists(path, sizeof(path), name, prop) == 0) {
+            goto found;
+        }
+    }
+
+    /* Nothing found, try the default */
+    if (hw_module_exists(path, sizeof(path), name, "default") == 0) {
+        goto found;
+    }
+
+    return -ENOENT;
+
+found:
+    /* load the module, if this fails, we're doomed, and we should not try
+     * to load a different variant. */
+    return load(class_id, path, module);
+}
+
+int hw_get_module(const char *id, const struct hw_module_t **module)
+{
+    return hw_get_module_by_class(id, NULL, module);
+}