backends: Introduce chr-testdev

From: Paolo Bonzini <pbonzini@redhat.com>

chr-testdev enables a virtio serial channel to be used for guest
initiated qemu exits. hw/misc/debugexit already enables guest
initiated qemu exits, but only for PC targets. chr-testdev supports
any virtio-capable target. kvm-unit-tests/arm is already making use
of this backend.

Currently there is a single command implemented, "q".  It takes a
(prefix) argument for the exit code, thus an exit is implemented by
writing, e.g. "1q", to the virtio-serial port.

It can be used as:
   $QEMU ... \
     -device virtio-serial-device \
     -device virtserialport,chardev=ctd -chardev testdev,id=ctd

or, use:
   $QEMU ... \
     -device virtio-serial-device \
     -device virtconsole,chardev=ctd -chardev testdev,id=ctd

to bind it to virtio-serial port0.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

2 files changed, 8 insertions, 0 deletions

diff --git a/stubs/Makefile.objs b/stubs/Makefile.objs
index 528e161..5e347d0 100644
--- a/stubs/Makefile.objs
+++ b/stubs/Makefile.objs
@@ -2,6 +2,7 @@ stub-obj-y += arch-query-cpu-def.o
 stub-obj-y += bdrv-commit-all.o
 stub-obj-y += chr-baum-init.o
 stub-obj-y += chr-msmouse.o
+stub-obj-y += chr-testdev.o
 stub-obj-y += clock-warp.o
 stub-obj-y += cpu-get-clock.o
 stub-obj-y += cpu-get-icount.o
diff --git a/stubs/chr-testdev.c b/stubs/chr-testdev.c
new file mode 100644
index 0000000..23112a2
--- /dev/null
+++ b/stubs/chr-testdev.c
@@ -0,0 +1,7 @@
+#include "qemu-common.h"
+#include "sysemu/char.h"
+
+CharDriverState *chr_testdev_init(void)
+{
+    return 0;
+}