Support default block interfaces per QEMUMachine

There are QEMUMachines that have neither IF_IDE nor IF_SCSI as a
default/standard interface to their block devices / drives. Therefore,
this patch introduces a new field default_block_type per QEMUMachine
struct. The prior use_scsi field becomes thereby obsolete and is
replaced through .default_block_type = IF_SCSI.

This patch also changes the default for s390x to IF_VIRTIO and
removes an early hack that converts IF_IDE drives.
Other parties have already claimed interest (e.g. IF_SD for exynos)

To create a sane default, for machines that dont specify a
default_block_type, this patch makes IF_IDE = 0 and IF_NONE = 1.
I checked all users of IF_NONE (blockdev.c and ww/device-hotplug.c)
as well as IF_IDE and it seems that it is ok to change the defines -
in other words, I found no obvious (to me) assumption in the code
regarding IF_NONE==0. IF_NONE is only set if there is an
explicit if=none. Without if=* the interface becomes IF_DEFAULT.

I would suggest to have some additional care, e.g. by letting
this patch sit some days in the block tree.

Based on an initial patch from Einar Lueck <elelueck@de.ibm.com>

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
CC: Igor Mitsyanko <i.mitsyanko@samsung.com>
CC: Markus Armbruster <armbru@redhat.com>
CC: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Alexander Graf <agraf@suse.de>
Acked-by: Igor Mitsyanko <i.mitsyanko@samsung.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/blockdev.h b/blockdev.h
index 5f27b643be..d73d552a98 100644
--- a/blockdev.h
+++ b/blockdev.h
@@ -19,8 +19,13 @@ void blockdev_auto_del(BlockDriverState *bs);
 
 typedef enum {
     IF_DEFAULT = -1,            /* for use with drive_add() only */
+    /*
+     * IF_IDE must be zero, because we want QEMUMachine member
+     * block_default_type to default-initialize to IF_IDE
+     */
+    IF_IDE = 0,
     IF_NONE,
-    IF_IDE, IF_SCSI, IF_FLOPPY, IF_PFLASH, IF_MTD, IF_SD, IF_VIRTIO, IF_XEN,
+    IF_SCSI, IF_FLOPPY, IF_PFLASH, IF_MTD, IF_SD, IF_VIRTIO, IF_XEN,
     IF_COUNT
 } BlockInterfaceType;
 
@@ -51,7 +56,7 @@ DriveInfo *drive_get_by_blockdev(BlockDriverState *bs);
 QemuOpts *drive_def(const char *optstr);
 QemuOpts *drive_add(BlockInterfaceType type, int index, const char *file,
                     const char *optstr);
-DriveInfo *drive_init(QemuOpts *arg, int default_to_scsi);
+DriveInfo *drive_init(QemuOpts *arg, BlockInterfaceType block_default_type);
 
 /* device-hotplug */