--- qemu-0.9.0/monitor.c
+++ qemu-0.9.0/monitor.c
@@ -362,9 +362,10 @@ static void do_eject(int force, const char *filename)
     eject_device(bs, force);
 }
 
-static void do_change(const char *device, const char *filename)
+static void do_change(const char *device, const char *filename, const char *fmt)
 {
     BlockDriverState *bs;
+    BlockDriver *drv = NULL;
     int i;
     char password[256];
 
@@ -373,9 +374,16 @@ static void do_change(const char *device, const char *filename)
         term_printf("device not found\n");
         return;
     }
+    if (fmt) {
+        drv = bdrv_find_format(fmt);
+        if (!drv) {
+            term_printf("invalid format %s\n", fmt);
+            return;
+        }
+    }
     if (eject_device(bs, 0) < 0)
         return;
-    bdrv_open(bs, filename, 0);
+    bdrv_open2(bs, filename, 0, drv);
     if (bdrv_is_encrypted(bs)) {
         term_printf("%s is encrypted.\n", device);
         for(i = 0; i < 3; i++) {
@@ -1195,8 +1203,8 @@ static term_cmd_t term_cmds[] = {
       "", "quit the emulator" },
     { "eject", "-fB", do_eject,
       "[-f] device", "eject a removable media (use -f to force it)" },
-    { "change", "BF", do_change,
-      "device filename", "change a removable media" },
+    { "change", "BFs?", do_change,
+      "device filename [format]", "change a removable media, optional format" },
     { "screendump", "F", do_screen_dump, 
       "filename", "save screen into PPM image 'filename'" },
     { "log", "s", do_log,
--- qemu-0.9.0/hw/usb-msd.c
+++ qemu-0.9.0/hw/usb-msd.c
@@ -510,17 +510,25 @@ static void usb_msd_handle_destroy(USBDevice *dev)
     qemu_free(s);
 }
 
-USBDevice *usb_msd_init(const char *filename)
+USBDevice *usb_msd_init(const char *filename, const char *fmt)
 {
     MSDState *s;
     BlockDriverState *bdrv;
+    BlockDriver *drv = NULL;
 
+    if (fmt) {
+        drv = bdrv_find_format(fmt);
+        if (!drv) {
+            fprintf(stderr, "%s: '%s' invalid format\n", __func__, fmt);
+            return NULL;
+        }
+    }
     s = qemu_mallocz(sizeof(MSDState));
     if (!s)
         return NULL;
 
     bdrv = bdrv_new("usb");
-    if (bdrv_open(bdrv, filename, 0) < 0)
+    if (bdrv_open2(bdrv, filename, 0, drv) < 0)
         goto fail;
     s->bs = bdrv;
 
--- qemu-0.9.0/hw/usb.h
+++ qemu-0.9.0/hw/usb.h
@@ -217,4 +217,4 @@ USBDevice *usb_mouse_init(void);
 USBDevice *usb_tablet_init(void);
 
 /* usb-msd.c */
-USBDevice *usb_msd_init(const char *filename);
+USBDevice *usb_msd_init(const char *filename, const char *fmt);
--- qemu-0.9.0/qemu-doc.texi
+++ qemu-0.9.0/qemu-doc.texi
@@ -1306,6 +1306,9 @@ This means qemu is able to report the mouse position without having
 to grab the mouse.  Also overrides the PS/2 mouse emulation when activated.
 @item @code{disk:file}
 Mass storage device based on @var{file} (@pxref{disk_images})
+@item diskformat:file,format=@var{format}
+Mass storage device based on file with specified image @var{format}.
+See -format for more information.
 @item @code{host:bus.addr}
 Pass through the host device identified by @var{bus.addr}
 (Linux only)
--- qemu-0.9.0/vl.c
+++ qemu-0.9.0/vl.c
@@ -3951,6 +3951,27 @@ void qemu_register_usb_port(USBPort *port, void *opaque, int index,
     free_usb_ports = port;
 }
 
+static const char *get_opt_value(char *buf, int buf_size, const char *p)
+{
+    char *q;
+
+    q = buf;
+    while (*p != '\0') {
+        if (*p == ',') {
+            if (*(p + 1) != ',')
+                break;
+            p++;
+        }
+        if (q && (q - buf) < buf_size - 1)
+            *q++ = *p;
+        p++;
+    }
+    if (q)
+        *q = '\0';
+
+    return p;
+}
+
 static int usb_device_add(const char *devname)
 {
     const char *p;
@@ -3967,7 +3967,18 @@ static int usb_device_add(const char *devname)
     } else if (!strcmp(devname, "tablet")) {
 	dev = usb_tablet_init();
     } else if (strstart(devname, "disk:", &p)) {
-        dev = usb_msd_init(p);
+        dev = usb_msd_init(p, NULL);
+    } else if (strstart(devname, "diskformat:", &p)) {
+        char file[1024];
+        char buf[128];
+        char *fmt = NULL;
+        p = get_opt_value(file, sizeof(file), p);
+        if (*p == ',') {
+            p++;
+            if (get_param_value(buf, sizeof(buf), "format", p))
+                fmt = buf;
+        }
+        dev = usb_msd_init(file, fmt);
     } else {
         return -1;
     }