modules/access/v4l2/lib.c

   1 /*****************************************************************************
   2  * lib.c : libv4l2 run-time
   3  *****************************************************************************
   4  * Copyright (C) 2012 Rémi Denis-Courmont
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU Lesser General Public License as published by
   8  * the Free Software Foundation; either version 2.1 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14  * GNU Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public License
  17  * along with this program; if not, write to the Free Software Foundation,
  18  * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  19  *****************************************************************************/
  20
  21 #ifdef HAVE_CONFIG_H
  22 # include "config.h"
  23 #endif
  24
  25 #include <dlfcn.h>
  26 #include <unistd.h>
  27 #include <sys/ioctl.h>
  28 #include <sys/mman.h>
  29
  30 #include <vlc_common.h>
  31
  32 #include "v4l2.h"
  33
  34 static int fd_open (int fd, int flags)
  35 {
  36     (void) flags;
  37     return fd;
  38 }
  39
  40 static void *v4l2_handle = NULL;
  41
  42 static int (*v4l2_fd_open_cb)(int, int) = fd_open;
  43 //int (*v4l2_open) (const char *, int, ...) = open;
  44 //int (*v4l2_dup) (const char *, int, ...) = dup;
  45 int (*v4l2_close) (int) = close;
  46 int (*v4l2_ioctl) (int, unsigned long int, ...) = ioctl;
  47 ssize_t (*v4l2_read) (int, void *, size_t) = read;
  48 //ssize_t (*v4l2_write) (int, const void *, size_t) = write;
  49 void * (*v4l2_mmap) (void *, size_t, int, int, int, int64_t) = mmap;
  50 int (*v4l2_munmap) (void *, size_t) = munmap;
  51
  52 static void v4l2_lib_load (void)
  53 {
  54     void *h;
  55
  56     h = dlopen ("libmediaclient.so", RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
  57     if (h == NULL)
  58         h = dlopen ("libv4l2.so.0", RTLD_LAZY | RTLD_LOCAL);
  59     if (h == NULL)
  60         return;
  61
  62     void *sym = dlsym(h, "v4l2_fd_open");
  63     if (sym != NULL)
  64         v4l2_fd_open_cb = sym;
  65
  66 #define SYM(name) \
  67     sym = dlsym (h, "v4l2_"#name); \
  68     if (sym != NULL) v4l2_##name = sym
  69
  70     /*SYM(open); SYM(dup);*/ SYM(close); SYM(ioctl);
  71     SYM(read); /*SYM(write);*/ SYM(mmap); SYM(munmap);
  72
  73     v4l2_handle = h;
  74 }
  75
  76 __attribute__((destructor))
  77 static void v4l2_lib_unload (void)
  78 {
  79     if (v4l2_handle != NULL)
  80         dlclose (v4l2_handle);
  81 }
  82
  83 int v4l2_fd_open(int fd, int flags)
  84 {
  85     static pthread_once_t once = PTHREAD_ONCE_INIT;
  86
  87     pthread_once(&once, v4l2_lib_load);
  88     return v4l2_fd_open_cb(fd, flags);
  89 }