runqemu: support booting ramfs-based images

Added support for booting ramfs-based images (e.g, poky-tiny) which
do not have block device support.

This fixes [YOCTO #2612].

(From OE-Core rev: b09c45f017da71ff966004752f8e926ea00ac451)

Signed-off-by: Scott Garman <scott.a.garman@intel.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/runqemu

@@ -26,6 +26,7 @@ usage() {
     echo "  KERNEL - the kernel image file to use"
     echo "  ROOTFS - the rootfs image file or nfsroot directory to use"
     echo "  MACHINE - the machine name (optional, autodetected from KERNEL filename if unspecified)"
+    echo "  RAMFS - boot a ramfs-based image"
     echo "  Simplified QEMU command-line options can be passed with:"
     echo "    nographic - disables video console"
     echo "    serial - enables a serial console on /dev/ttyS0"
@@ -37,6 +38,7 @@ usage() {
     echo "  $MYNAME qemuarm"
     echo "  $MYNAME qemux86-64 core-image-sato ext3"
     echo "  $MYNAME path/to/bzImage-qemux86.bin path/to/nfsrootdir/ serial"
+    echo "  $MYNAME qemux86 ramfs"
     echo "  $MYNAME qemux86 qemuparams=\"-m 256\""
     echo "  $MYNAME qemux86 bootparams=\"psplash=false\""
     exit 1
@@ -118,6 +120,10 @@ while true; do
                 LAZY_ROOTFS="true"
             fi
             ;;
+        "ramfs")
+            FSTYPE=cpio.gz
+            RAMFS=true
+            ;;
         "nographic")
             SCRIPT_QEMU_OPT="$SCRIPT_QEMU_OPT -nographic"
             SCRIPT_KERNEL_OPT="$SCRIPT_KERNEL_OPT console=ttyS0"

scripts/runqemu-internal

@@ -453,6 +453,11 @@ if [ "$MACHINE" = "akita" ]; then
     fi
 fi
 
+if [ "x$RAMFS" = "xtrue" ]; then
+    QEMUOPTIONS="-initrd $ROOTFS -nographic"
+    KERNCMDLINE="root=/dev/ram0"
+fi
+
 if [ "x$QEMUOPTIONS" = "x" ]; then
     echo "Error: Unable to support this combination of options"
     cleanup