blockdev: Set 'format' indicates non-empty drive

Creating an empty drive while specifying 'format' doesn't make sense.
The specified format driver would simply be ignored.

Make a set 'format' option an indication that a non-empty drive should
be created. This makes 'format' consistent with 'driver' and allows
using it with a block driver that doesn't need any other options (like
null-co/null-aio).
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>

blockdev.c

@@ -490,7 +490,6 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
     QDict *interval_dict = NULL;
     QList *interval_list = NULL;
     const char *id;
-    bool has_driver_specific_opts;
     BlockdevDetectZeroesOptions detect_zeroes =
         BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF;
     const char *throttling_group = NULL;
@@ -514,8 +513,6 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
         qdict_del(bs_opts, "id");
     }
 
-    has_driver_specific_opts = !!qdict_size(bs_opts);
-
     /* extract parameters */
     snapshot = qemu_opt_get_bool(opts, "snapshot", 0);
 
@@ -578,7 +575,7 @@ static BlockBackend *blockdev_init(const char *file, QDict *bs_opts,
     }
 
     /* init */
-    if ((!file || !*file) && !has_driver_specific_opts) {
+    if ((!file || !*file) && !qdict_size(bs_opts)) {
         BlockBackendRootState *blk_rs;
 
         blk = blk_new(qemu_opts_id(opts), errp);

tests/hd-geo-test.c

@@ -206,13 +206,13 @@ static int setup_ide(int argc, char *argv[], int argv_sz,
 {
     char *s1, *s2, *s3;
 
-    s1 = g_strdup_printf("-drive id=drive%d,if=%s,format=raw",
+    s1 = g_strdup_printf("-drive id=drive%d,if=%s",
                          ide_idx, dev ? "none" : "ide");
     s2 = dev ? g_strdup("") : g_strdup_printf(",index=%d", ide_idx);
 
     if (img_secs[img_idx] >= 0) {
         setup_mbr(img_idx, mbr);
-        s3 = g_strdup_printf(",file=%s", img_file_name[img_idx]);
+        s3 = g_strdup_printf(",format=raw,file=%s", img_file_name[img_idx]);
     } else {
         s3 = g_strdup(",media=cdrom");
     }

tests/qemu-iotests/iotests.py

@@ -148,12 +148,12 @@ class VM(object):
     def add_drive(self, path, opts='', interface='virtio'):
         '''Add a virtio-blk drive to the VM'''
         options = ['if=%s' % interface,
-                   'format=%s' % imgfmt,
                    'cache=%s' % cachemode,
                    'id=drive%d' % self._num_drives]
 
         if path is not None:
             options.append('file=%s' % path)
+            options.append('format=%s' % imgfmt)
 
         if opts:
             options.append(opts)