QOM right now does not have a way to communicate values for qdev properties except as strings. This is bad.
This patch improves the Property implementation so that properties export a visitor-based interface in addition to the string-based interface. The new interface can then be registered as a "static" property. It's called static because it uses a struct field for storage and, as such, should be present in all objects of a given class. Patches 1-2 are bugfixes and patches 3-4 are cleanups. Example using qmp-shell: x86_64-softmmu/qemu-system-x86_64 \ -hda ~/test.img -snapshot -S \ -qmp unix:/tmp/server.sock,server,nowait \ -netdev type=user,id=net -device virtio-net-pci,netdev=net,id=net \ -net user,vlan=1 -device virtio-net-pci,id=net2,vlan=1 \ -chardev id=stdio,backend=stdio -device isa-serial,chardev=stdio,id=serial Boolean properties: (QEMU) qom-get path=/i440fx/piix3 property=command_serr_enable {u'return': True} (QEMU) qom-get path=/i440fx/piix3 property=legacy<command_serr_enable> {u'return': u'on'} PCI address properties (perhaps will disappear later, but not yet): (QEMU) qom-get path=/i440fx/piix3 property=addr {u'return': u'01.0'} (QEMU) qom-get path=/i440fx/piix3 property=legacy-addr {u'return': u'01.0'} String properties (NULL mapped to empty string): (QEMU) qom-get path=/vga property=romfile {u'return': u'vgabios-cirrus.bin'} (QEMU) qom-get path=/vga property=legacy-romfile {u'return': u'"vgabios-cirrus.bin"'} (QEMU) qom-get path=/i440fx/piix3 property=romfile {u'return': u''} (QEMU) qom-get path=/i440fx/piix3 property=legacy-romfile {u'return': u'<null>'} MAC properties: (QEMU) qom-get path=/peripheral/net property=mac {u'return': u'52:54:00:12:34:56'} (QEMU) qom-get path=/peripheral/net property=legacy-mac {u'return': u'52:54:00:12:34:56'} (QEMU) qom-set path=/peripheral/net property=mac value=52-54-00-12-34-57 {u'error': {u'data': {}, u'class': u'PermissionDenied', u'desc': u'Insufficient permission to perform this operation'}} Network properties: (QEMU) qom-get path=/peripheral/net property=netdev {u'return': u'net'} (QEMU) qom-get path=/peripheral/net property=legacy-netdev {u'return': u'net'} VLAN properties: (QEMU) qom-get path=/peripheral/net property=vlan {u'return': -1} (QEMU) qom-get path=/peripheral/net property=legacy-vlan {u'return': u'<null>'} (QEMU) qom-get path=/peripheral/net2 property=vlan {u'return': 1} (QEMU) qom-get path=/peripheral/net2 property=legacy-vlan {u'return': u'1'} Chardev properties: (QEMU) qom-get path=/peripheral/serial property=chardev {u'return': u'stdio'} (QEMU) qom-get path=/peripheral/serial property=legacy-chardev {u'return': u'stdio'} Legacy hex32 properties: (QEMU) qom-get path=/peripheral/serial property=iobase {u'return': 1016} (QEMU) qom-get path=/peripheral/serial property=legacy-iobase {u'return': u'0x3f8'} Examples of setting properties (after disabling the DEV_STATE_CREATED check for testing only): (QEMU) qom-set path=/peripheral/net2 property=vlan value=-1 {u'return': {}} (QEMU) qom-get path=/peripheral/net2 property=vlan {u'return': -1} (QEMU) qom-get path=/peripheral/net2 property=legacy-vlan {u'return': u'<null>'} (QEMU) qom-set path=/peripheral/serial property=iobase value=760 {u'return': {}} (QEMU) qom-get path=/peripheral/serial property=iobase {u'return': 760} (QEMU) qom-get path=/peripheral/serial property=legacy-iobase {u'return': u'0x2f8'} v2->v3: Tweaks to patch 4. v1->v2: New "qom: interpret the return value when setting legacy properties". Always pass a value to the visitor when there is no error. Handle empty strings as NULL. Did not change QERR_PROPERTY_VALUE_OUT_OF_RANGE because it is consistent with other QERR_PROPERTY_* errors, now used by QOM too. Paolo Bonzini (8): qapi: protect against NULL QObject in qmp_input_get_object qom: fix swapped parameters qom: push permission checks up into qdev_property_add_legacy qom: interpret the return value when setting legacy properties qom: introduce QERR_PROPERTY_VALUE_OUT_OF_RANGE qom: introduce get/set methods for Property qom: distinguish "legacy" property type name from QOM type name qom: register qdev properties also as non-legacy properties hw/qdev-addr.c | 41 +++++ hw/qdev-properties.c | 407 +++++++++++++++++++++++++++++++++++++++++++-- hw/qdev.c | 84 ++++++---- hw/qdev.h | 14 +- qapi/qmp-input-visitor.c | 10 +- qerror.c | 5 + qerror.h | 3 + 7 files changed, 502 insertions(+), 62 deletions(-) -- 1.7.7.1