[PATCH v2 2/3] qemu: retain default trace backend if 'ust' is not enabled

[Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>]

The qemu build system enables the 'log' trace backend by default, if no
explicit choice was made with '--enable-trace-backend=CHOICE'.

However, the qemu recipe uses the following PACKAGECONFIG line:
    PACKAGECONFIG[ust] = "--enable-trace-backend=ust,--enable-trace-backend=nop,lttng-ust,"

which means that the 'nop' trace backend will be explicitly selected if the
'ust' feature is not enabled. The 'nop' backend removes almost all trace
points at compile time, and thus basically means 'disable tracing'.

To retain the default trace backend if 'ust' is not enabled, the above
PACKAGECONFIG line should either explicitly fall back to the 'log' backend,
or not provide any value for the 'disabled' case. This commit chooses the
latter to not make any assumption about the upstream default.

Signed-off-by: Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>
---
 meta/recipes-devtools/qemu/qemu.inc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/meta/recipes-devtools/qemu/qemu.inc b/meta/recipes-devtools/qemu/qemu.inc
index 36b2f14638..10001c3e66 100644
--- a/meta/recipes-devtools/qemu/qemu.inc
+++ b/meta/recipes-devtools/qemu/qemu.inc
@@ -208,7 +208,7 @@ PACKAGECONFIG[libudev] = "--enable-libudev,--disable-libudev,eudev"
 PACKAGECONFIG[attr] = "--enable-attr,--disable-attr,attr,"
 PACKAGECONFIG[rbd] = "--enable-rbd,--disable-rbd,ceph,ceph"
 PACKAGECONFIG[vhost] = "--enable-vhost-net,--disable-vhost-net,,"
-PACKAGECONFIG[ust] = "--enable-trace-backend=ust,--enable-trace-backend=nop,lttng-ust,"
+PACKAGECONFIG[ust] = "--enable-trace-backend=ust,,lttng-ust,"
 PACKAGECONFIG[pie] = "--enable-pie,--disable-pie,,"
 PACKAGECONFIG[seccomp] = "--enable-seccomp,--disable-seccomp,libseccomp"
 # libnfs is currently provided by meta-kodi
-- 
2.39.2