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      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 (at) 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    { "gbm_gallium_drm.so", NULL },
     49 };
     50 
     51 static const void *
     52 load_backend(const struct backend_desc *backend)
     53 {
     54    char path[PATH_MAX];
     55    const void *init = NULL;
     56    void *module;
     57    const char *name;
     58    const char *entrypoint = "gbm_backend";
     59 
     60    if (backend == NULL)
     61       return NULL;
     62 
     63    name = backend->name;
     64 
     65    if (backend->builtin) {
     66       init = backend->builtin;
     67    } else {
     68       if (name[0] != '/')
     69          snprintf(path, sizeof path, MODULEDIR "/%s", name);
     70       else
     71          snprintf(path, sizeof path, "%s", name);
     72 
     73       module = dlopen(path, RTLD_NOW | RTLD_GLOBAL);
     74       if (!module) {
     75          fprintf(stderr,
     76                  "failed to load module: %s\n", dlerror());
     77          return NULL;
     78       }
     79 
     80       init = dlsym(module, entrypoint);
     81       if (!init)
     82          return NULL;
     83    }
     84 
     85    return init;
     86 }
     87 
     88 static const struct backend_desc *
     89 find_backend(const char *name)
     90 {
     91    const struct backend_desc *backend = NULL;
     92    int i;
     93 
     94    for (i = 0; i < ARRAY_SIZE(backends); ++i) {
     95       if (strcmp(backends[i].name, name) == 0) {
     96          backend = &backends[i];
     97          break;
     98       }
     99    }
    100 
    101    return backend;
    102 }
    103 
    104 struct gbm_device *
    105 _gbm_create_device(int fd)
    106 {
    107    const struct gbm_backend *backend = NULL;
    108    struct gbm_device *dev = NULL;
    109    int i;
    110    const char *b;
    111 
    112    b = getenv("GBM_BACKEND");
    113    if (b)
    114       backend = load_backend(find_backend(b));
    115 
    116    if (backend)
    117       dev = backend->create_device(fd);
    118 
    119    for (i = 0; i < ARRAY_SIZE(backends) && dev == NULL; ++i) {
    120       backend = load_backend(&backends[i]);
    121       if (backend == NULL)
    122          continue;
    123 
    124       dev = backend->create_device(fd);
    125    }
    126 
    127    return dev;
    128 }
    129