v4l2: simplify dynamic loading of libv4l2

modules/access/Makefile.am

@@ -175,7 +175,7 @@ libv4l2_plugin_la_SOURCES = \
 	access/v4l2/v4l2.h
 libv4l2_plugin_la_CPPFLAGS = $(AM_CPPFLAGS) -I$(srcdir)/access/v4l2
 libv4l2_plugin_la_CFLAGS = $(AM_CFLAGS) $(ZVBI_CFLAGS)
-libv4l2_plugin_la_LIBADD = $(LIBDL) $(LIBM) $(ZVBI_LIBS) $(LIBPTHREAD)
+libv4l2_plugin_la_LIBADD = $(LIBDL) $(LIBM) $(ZVBI_LIBS)
 if HAVE_V4L2
 access_LTLIBRARIES += libv4l2_plugin.la
 endif

modules/access/v4l2/lib.c

@@ -22,7 +22,6 @@
 # include "config.h"
 #endif
 
-#include <pthread.h>
 #include <dlfcn.h>
 #include <unistd.h>
 #include <sys/ioctl.h>
@@ -32,48 +31,40 @@
 
 #include "v4l2.h"
 
-static void *v4l2_handle = NULL;
-static int (*v4l2_fd_open_) (int, int);
-int (*v4l2_close) (int);
-int (*v4l2_ioctl) (int, unsigned long int, ...);
-ssize_t (*v4l2_read) (int, void *, size_t);
-void * (*v4l2_mmap) (void *, size_t, int, int, int, int64_t);
-int (*v4l2_munmap) (void *, size_t);
-
 static int fd_open (int fd, int flags)
 {
     (void) flags;
     return fd;
 }
 
+static void *v4l2_handle = NULL;
+
+int (*v4l2_fd_open) (int, int) = fd_open;
+//int (*v4l2_open) (const char *, int, ...) = open;
+//int (*v4l2_dup) (const char *, int, ...) = dup;
+int (*v4l2_close) (int) = close;
+int (*v4l2_ioctl) (int, unsigned long int, ...) = ioctl;
+ssize_t (*v4l2_read) (int, void *, size_t) = read;
+//ssize_t (*v4l2_write) (int, const void *, size_t) = write;
+void * (*v4l2_mmap) (void *, size_t, int, int, int, int64_t) = mmap;
+int (*v4l2_munmap) (void *, size_t) = munmap;
+
+__attribute__((constructor))
 static void v4l2_lib_load (void)
 {
     void *h = dlopen ("libv4l2.so.0", RTLD_LAZY | RTLD_LOCAL);
     if (h == NULL)
-        goto fallback;
+        return;
 
-    v4l2_fd_open_ = dlsym (h, "v4l2_fd_open");
-    v4l2_close = dlsym (h, "v4l2_close");
-    v4l2_ioctl = dlsym (h, "v4l2_ioctl");
-    v4l2_read = dlsym (h, "v4l2_read");
-    v4l2_mmap = dlsym (h, "v4l2_mmap");
-    v4l2_munmap = dlsym (h, "v4l2_munmap");
+    void *sym;
+#define SYM(name) \
+    sym = dlsym (h, "v4l2_"#name); \
+    if (sym != NULL) v4l2_##name = sym
 
-    if (v4l2_fd_open_ != NULL && v4l2_close != NULL && v4l2_ioctl != NULL
-     && v4l2_read != NULL && v4l2_mmap != NULL && v4l2_munmap != NULL)
-    {
-        v4l2_handle = h;
-        return;
-    }
+    SYM(fd_open); /*SYM(open); SYM(dup);*/ SYM(close); SYM(ioctl);
+    SYM(read); /*SYM(write);*/ SYM(mmap); SYM(munmap);
 
-    dlclose (h);
-fallback:
-    v4l2_fd_open_ = fd_open;
-    v4l2_close = close;
-    v4l2_ioctl = ioctl;
-    v4l2_read = read;
-    v4l2_mmap = mmap;
-    v4l2_munmap = munmap;
+    v4l2_handle = h;
 }
 
 __attribute__((destructor))
@@ -82,11 +73,3 @@ static void v4l2_lib_unload (void)
     if (v4l2_handle != NULL)
         dlclose (v4l2_handle);
 }
-
-int v4l2_fd_open (int fd, int flags)
-{
-    static pthread_once_t once = PTHREAD_ONCE_INIT;
-
-    pthread_once (&once, v4l2_lib_load);
-    return v4l2_fd_open_ (fd, flags);
-}

modules/access/v4l2/v4l2.h

@@ -21,7 +21,7 @@
 #include <linux/videodev2.h>
 
 /* libv4l2 functions */
-extern int v4l2_fd_open (int, int);
+extern int (*v4l2_fd_open) (int, int);
 extern int (*v4l2_close) (int);
 extern int (*v4l2_ioctl) (int, unsigned long int, ...);
 extern ssize_t (*v4l2_read) (int, void *, size_t);