opencv: rework V4L/libv4l support

Starting with the 2.4.7 release, for V4L support, OpenCV does not
requires a libv4l dependency for its V4L support.

So, it now provides 2 distincts knobs for this: WITH_V4L and a new
one: WITH_LIBV4L.

This patch takes advantage of this new knob and libv4l support is
now automatically enabled only if the libv4l package is enabled.

In OpenCV, the logic behind this is:
- using libv4l if available,
- otherwise, use v4l2 or v4l API from the kernel if available.

[Thomas: remove gratuituous reformating, as suggested by Yann.]

Signed-off-by: Samuel Martin <s.martin49@gmail.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/opencv/Config.in

@@ -205,16 +205,10 @@ config BR2_PACKAGE_OPENCV_WITH_TIFF
 
 config BR2_PACKAGE_OPENCV_WITH_V4L
 	bool "v4l support"
-	depends on BR2_LARGEFILE
-	depends on BR2_TOOLCHAIN_HAS_THREADS
-	depends on BR2_USE_MMU # libv4l fork
-	select BR2_PACKAGE_LIBV4L
 	help
 	  Enable Video 4 Linux support.
 
-comment "v4l support needs a toolchain w/ largefile, threads"
-	depends on !BR2_LARGEFILE || !BR2_TOOLCHAIN_HAS_THREADS
-	depends on BR2_USE_MMU
+	  If the package libv4l is enabled, its support is automatically enabled.
 
 comment "Install options"
 

package/opencv/opencv.mk

@@ -220,8 +220,10 @@ OPENCV_CONF_OPT += -DWITH_TIFF=OFF
 endif
 
 ifeq ($(BR2_PACKAGE_OPENCV_WITH_V4L),y)
-OPENCV_CONF_OPT += -DWITH_V4L=ON -DWITH_LIBV4L=ON
-OPENCV_DEPENDENCIES += libv4l
+OPENCV_CONF_OPT += \
+	-DWITH_V4L=ON \
+	-DWITH_LIBV4L=$(if $(BR2_PACKAGE_LIBV4L),ON,OFF)
+OPENCV_DEPENDENCIES += $(if $(BR2_PACKAGE_LIBV4L),libv4l)
 else
 OPENCV_CONF_OPT += -DWITH_V4L=OFF -DWITH_LIBV4L=OFF
 endif