qemu.inc: Change kernel provider assignment to a weaker one

Currently we have local.conf included before qemu.inc, and ${DISTRO}.conf
after qemu.inc. They both possibly specify their expected kernel providers.
To let other config files override it in real use, this commit changes
kernel provider assignment to ??= .

Signed-off-by: He Zhe <zhe.he@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>

diff --git a/meta/conf/machine/include/qemu.inc b/meta/conf/machine/include/qemu.inc
index aa332fecc2c0c8b7a7bc86956cd9052ec1c969fd..5050e41066e12e084b89d45e5f2aa3b7b742c2bd 100644 (file)
--- a/meta/conf/machine/include/qemu.inc
+++ b/meta/conf/machine/include/qemu.inc
@@ -19,7 +19,7 @@ IMAGE_FSTYPES += "tar.bz2 ext4"
 RDEPENDS_${KERNEL_PACKAGE_NAME}-base = ""
 
 # Use a common kernel recipe for all QEMU machines
-PREFERRED_PROVIDER_virtual/kernel ?= "linux-yocto"
+PREFERRED_PROVIDER_virtual/kernel ??= "linux-yocto"
 
 EXTRA_IMAGEDEPENDS += "qemu-native qemu-helper-native"