distro_bootcmd: add VirtIO distro boot command

Add a boot command to distro boot to support disks connected over the
VirtIO bus. The boot command uses the shared block environment.

Signed-off-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Alexander Graf <agraf@suse.de>

doc/README.distro

@@ -292,7 +292,7 @@ Each entry in the macro defines a single boot device (e.g. a specific eMMC
 device or SD card) or type of boot device (e.g. USB disk). The parameters to
 the func macro (passed in by the internal implementation of the header) are:
 
-- Upper-case disk type (MMC, SATA, SCSI, IDE, USB, DHCP, PXE).
+- Upper-case disk type (MMC, SATA, SCSI, IDE, USB, DHCP, PXE, VIRTIO).
 - Lower-case disk type (same options as above).
 - ID of the specific disk (MMC only) or ignored for other types.
 
@@ -398,6 +398,7 @@ The list of possible targets consists of:
   * scsi
   * ide
   * usb
+  * virtio
 
 Other *boot* variables than the ones defined above are only for internal use
 of the boot environment and are not guaranteed to exist or work in the same

include/config_distro_bootcmd.h

@@ -242,6 +242,18 @@
 	BOOT_TARGET_DEVICES_references_USB_without_CONFIG_CMD_USB
 #endif
 
+#ifdef CONFIG_CMD_VIRTIO
+#define BOOTENV_SHARED_VIRTIO	BOOTENV_SHARED_BLKDEV(virtio)
+#define BOOTENV_DEV_VIRTIO	BOOTENV_DEV_BLKDEV
+#define BOOTENV_DEV_NAME_VIRTIO	BOOTENV_DEV_NAME_BLKDEV
+#else
+#define BOOTENV_SHARED_VIRTIO
+#define BOOTENV_DEV_VIRTIO \
+	BOOT_TARGET_DEVICES_references_VIRTIO_without_CONFIG_CMD_VIRTIO
+#define BOOTENV_DEV_NAME_VIRTIO \
+	BOOT_TARGET_DEVICES_references_VIRTIO_without_CONFIG_CMD_VIRTIO
+#endif
+
 #if defined(CONFIG_CMD_DHCP)
 #if defined(CONFIG_EFI_LOADER)
 /* http://www.iana.org/assignments/dhcpv6-parameters/dhcpv6-parameters.xml */
@@ -350,6 +362,7 @@
 	BOOTENV_SHARED_IDE \
 	BOOTENV_SHARED_UBIFS \
 	BOOTENV_SHARED_EFI \
+	BOOTENV_SHARED_VIRTIO \
 	"boot_prefixes=/ /boot/\0" \
 	"boot_scripts=boot.scr.uimg boot.scr\0" \
 	"boot_script_dhcp=boot.scr.uimg\0" \