block QMP: Deprecate query-block's "type", drop info block's "type="

query-block's specification documents response member "type" with
values "hd", "cdrom", "floppy", "unknown".

Its value is unreliable: a block device used as floppy has type
"floppy" if created with if=floppy, but type "hd" if created with
if=none.

That's because with if=none, the type is at best a declaration of
intent: the drive can be connected to any guest device.  Its type is
really the guest device's business.  Reporting it here is wrong.

No known user of QMP uses "type".  It's unlikely that any unknown
users exist, because its value is useless unless you know how the
block device was created.  But then you also know the true value.

Fixing the broken value risks breaking (hypothetical!) clients that
somehow rely on the current behavior.  Not fixing the value risks
breaking (hypothetical!) clients that rely on the value to be
accurate.  Can't entirely avoid hypothetical lossage.  Change the
value to be always "unknown".

This makes "info block" always report "type=unknown".  Pointless.
Change it to not report the type.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 6 insertions, 5 deletions

diff --git a/qmp-commands.hx b/qmp-commands.hx
index fbd98ee295..a9f109a391 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -1039,7 +1039,8 @@ Each json-object contain the following:
 
 - "device": device name (json-string)
 - "type": device type (json-string)
-         - Possible values: "hd", "cdrom", "floppy", "unknown"
+         - deprecated, retained for backward compatibility
+         - Possible values: "unknown"
 - "removable": true if the device is removable, false otherwise (json-bool)
 - "locked": true if the device is locked, false otherwise (json-bool)
 - "inserted": only present if the device is inserted, it is a json-object
@@ -1070,25 +1071,25 @@ Example:
                "encrypted":false,
                "file":"disks/test.img"
             },
-            "type":"hd"
+            "type":"unknown"
          },
          {
             "device":"ide1-cd0",
             "locked":false,
             "removable":true,
-            "type":"cdrom"
+            "type":"unknown"
          },
          {
             "device":"floppy0",
             "locked":false,
             "removable":true,
-            "type": "floppy"
+            "type":"unknown"
          },
          {
             "device":"sd0",
             "locked":false,
             "removable":true,
-            "type":"floppy"
+            "type":"unknown"
          }
       ]
    }