package/sdl2: rework KMS/DRM video driver dependencies

The KMS/DRM video driver of SDL2 can currently only be enabled when
mesa3d is the OpenGL provider, as the option has a dependency on
BR2_PACKAGE_MESA3D_GBM. Now that we have a libgbm virtual package and
BR2_PACKAGE_HAS_LIBGBM, we can do better.

However, this has uncovered a number of additional related issues that
are resolved at the same time. Here are some details:

 * the 'depends on BR2_PACKAGE_LIBDRM' is changed to a select, as we
   normally do for library dependencies. Due to this, we inherit a
   BR2_TOOLCHAIN_HAS_THREADS dependency.

 * the 'depends on BR2_PACKAGE_MESA3D_GBM' is changed to 'depends on
   BR2_PACKAGE_HAS_LIBGBM', and the 'mesa3d' dependency is changed to
   'libgbm'.

 * the KMS/DRM video driver in SDL2 needs EGL (hence the additional
   'depends on BR2_PACKAGE_HAS_LIBEGL' and the libegbl dependency is
   added in the .mk file). But in turn, EGL support is only checked
   when either OpenGL or OpenGLES support is enabled in SDL2, which is
   why we add logic to select the appropriate options.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
[yann.morin.1998@free.fr:
  - fix dependency on comment (invert the symbol dependencies)
  - split comment
]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/sdl2/Config.in

@@ -31,14 +31,19 @@ comment "X11 video driver needs X.org"
 
 config BR2_PACKAGE_SDL2_KMSDRM
 	bool "KMS/DRM video driver"
-	depends on BR2_PACKAGE_LIBDRM
-	depends on BR2_PACKAGE_MESA3D_GBM
+	depends on BR2_TOOLCHAIN_HAS_THREADS  # libdrm
+	depends on BR2_PACKAGE_HAS_LIBGBM
+	depends on BR2_PACKAGE_HAS_LIBEGL
+	depends on BR2_PACKAGE_SDL2_OPENGL || BR2_PACKAGE_SDL2_OPENGLES
+	select BR2_PACKAGE_LIBDRM
 
-comment "KMS/DRM video driver needs libdrm"
-	depends on !BR2_PACKAGE_LIBDRM
+comment "KMS/DRM video driver needs a toolchain w/ threads"
+	depends on !BR2_TOOLCHAIN_HAS_THREADS
 
-comment "KMS/DRM video driver needs mesa3d w/ GBM"
-	depends on !BR2_PACKAGE_MESA3D_GBM
+comment "KMS/DRM video driver needs a GBM provider, and OpenGL or OpenGLES+EGL"
+	depends on !BR2_PACKAGE_HAS_LIBGBM || \
+		!BR2_PACKAGE_HAS_LIBEGL || \
+		!(BR2_PACKAGE_SDL2_OPENGL || BR2_PACKAGE_SDL2_OPENGLES)
 
 config BR2_PACKAGE_SDL2_OPENGL
 	bool "OpenGL (GLX)"

package/sdl2/sdl2.mk

@@ -175,7 +175,7 @@ SDL2_CONF_OPTS += --disable-alsa
 endif
 
 ifeq ($(BR2_PACKAGE_SDL2_KMSDRM),y)
-SDL2_DEPENDENCIES += libdrm mesa3d
+SDL2_DEPENDENCIES += libdrm libgbm libegl
 SDL2_CONF_OPTS += --enable-video-kmsdrm
 else
 SDL2_CONF_OPTS += --disable-video-kmsdrm