src/gbm/main/backend.c

   1 /*
   2  * Copyright © 2011 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  16  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  17  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  18  * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
  19  * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
  20  * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  22  * DEALINGS IN THE SOFTWARE.
  23  *
  24  * Authors:
  25  *    Benjamin Franzke <benjaminfranzke@googlemail.com>
  26  */
  27
  28 #include <stdio.h>
  29 #include <stddef.h>
  30 #include <stdlib.h>
  31 #include <string.h>
  32 #include <limits.h>
  33 #include <dlfcn.h>
  34
  35 #include "backend.h"
  36
  37 #define ARRAY_SIZE(a) (sizeof(a)/sizeof((a)[0]))
  38
  39 extern const struct gbm_backend gbm_dri_backend;
  40
  41 struct backend_desc {
  42    const char *name;
  43    const struct gbm_backend *builtin;
  44 };
  45
  46 static const struct backend_desc backends[] = {
  47    { "gbm_dri.so", &gbm_dri_backend },
  48 };
  49
  50 static const void *
  51 load_backend(const struct backend_desc *backend)
  52 {
  53    char path[PATH_MAX];
  54    const void *init = NULL;
  55    void *module;
  56    const char *name;
  57    const char *entrypoint = "gbm_backend";
  58
  59    if (backend == NULL)
  60       return NULL;
  61
  62    name = backend->name;
  63
  64    if (backend->builtin) {
  65       init = backend->builtin;
  66    } else {
  67       if (name[0] != '/')
  68          snprintf(path, sizeof path, MODULEDIR "/%s", name);
  69       else
  70          snprintf(path, sizeof path, "%s", name);
  71
  72       module = dlopen(path, RTLD_NOW | RTLD_GLOBAL);
  73       if (!module) {
  74          fprintf(stderr,
  75                  "failed to load module: %s\n", dlerror());
  76          return NULL;
  77       }
  78
  79       init = dlsym(module, entrypoint);
  80       if (!init)
  81          return NULL;
  82    }
  83
  84    return init;
  85 }
  86
  87 static const struct backend_desc *
  88 find_backend(const char *name)
  89 {
  90    const struct backend_desc *backend = NULL;
  91    int i;
  92
  93    for (i = 0; i < ARRAY_SIZE(backends); ++i) {
  94       if (strcmp(backends[i].name, name) == 0) {
  95          backend = &backends[i];
  96          break;
  97       }
  98    }
  99
 100    return backend;
 101 }
 102
 103 struct gbm_device *
 104 _gbm_create_device(int fd)
 105 {
 106    const struct gbm_backend *backend = NULL;
 107    struct gbm_device *dev = NULL;
 108    int i;
 109    const char *b;
 110
 111    b = getenv("GBM_BACKEND");
 112    if (b)
 113       backend = load_backend(find_backend(b));
 114
 115    if (backend)
 116       dev = backend->create_device(fd);
 117
 118    for (i = 0; i < ARRAY_SIZE(backends) && dev == NULL; ++i) {
 119       backend = load_backend(&backends[i]);
 120       if (backend == NULL)
 121          continue;
 122
 123       dev = backend->create_device(fd);
 124    }
 125
 126    return dev;
 127 }