vl: Deprecate -virtfs_synth

The synth fsdriver never got used for anything else but the QTest
testcase for VirtIO 9P. And even there, QTest uses -fsdev synth and
-device virtio-9p-... directly.

Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>

qemu-deprecated.texi

@@ -72,6 +72,11 @@ backend settings instead of environment variables.  To ease migration to
 the new format, the ``-audiodev-help'' option can be used to convert
 the current values of the environment variables to ``-audiodev'' options.
 
+@subsection -virtfs_synth (since 4.1)
+
+The ``-virtfs_synth'' argument is now deprecated. Please use ``-fsdev synth''
+and ``-device virtio-9p-...'' instead.
+
 @section QEMU Machine Protocol (QMP) commands
 
 @subsection block-dirty-bitmap-add "autoload" parameter (since 2.12.0)

qemu-options.hx

@@ -1368,7 +1368,8 @@ DEF("virtfs_synth", 0, QEMU_OPTION_virtfs_synth,
 STEXI
 @item -virtfs_synth
 @findex -virtfs_synth
-Create synthetic file system image
+Create synthetic file system image. Note that this option is now deprecated.
+Please use @code{-fsdev synth} and @code{-device virtio-9p-...} instead.
 ETEXI
 
 DEF("iscsi", HAS_ARG, QEMU_OPTION_iscsi,

vl.c

@@ -3535,6 +3535,10 @@ int main(int argc, char **argv, char **envp)
                 QemuOpts *fsdev;
                 QemuOpts *device;
 
+                warn_report("'-virtfs_synth' is deprecated, please use "
+                             "'-fsdev synth' and '-device virtio-9p-...' "
+                            "instead");
+
                 fsdev = qemu_opts_create(qemu_find_opts("fsdev"), "v_synth",
                                          1, NULL);
                 if (!fsdev) {