backend.c

/*
 * Copyright © 2011 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 *
 * Authors:
 *    Benjamin Franzke <benjaminfranzke@googlemail.com>
 */

#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <dlfcn.h>

#include "backend.h"

#define ARRAY_SIZE(a) (sizeof(a)/sizeof((a)[0]))

/* a more clever scheme would be to discover backends in a certain
 * directory..
 */
static const char *backends[] = {
      "libgbm_kms.so.1",
};

static const void *
load_backend(const char *name)
{
   char path[PATH_MAX];
   void *module;
   const char *entrypoint = "gbm_backend";

   if (name[0] != '/')
      snprintf(path, sizeof path, MODULEDIR "/%s", name);
   else
      snprintf(path, sizeof path, "%s", name);

   module = dlopen(path, RTLD_NOW | RTLD_GLOBAL);
   if (!module) {
      fprintf(stderr, "failed to load module: %s\n", dlerror());
      return NULL;
   }

   return dlsym(module, entrypoint);
}

struct gbm_device *
_gbm_create_device(int fd)
{
   const struct gbm_backend *backend = NULL;
   struct gbm_device *dev = NULL;
   int i;
   const char *b;

   b = getenv("GBM_BACKEND");
   if (b)
      backend = load_backend(b);

   if (backend)
      dev = backend->create_device(fd);

   for (i = 0; i < ARRAY_SIZE(backends) && dev == NULL; ++i) {
      backend = load_backend(backends[i]);
      if (backend == NULL)
         continue;
      fprintf(stderr, "loaded module: %s\n", backends[i]);
      dev = backend->create_device(fd);
   }
   
   return dev;
}