David Gibson <da...@gibson.dropbear.id.au> writes: > On Thu, Dec 03, 2015 at 04:30:31PM +0100, Markus Armbruster wrote: >> 1. Before commit 94649d4 "spapr: Don't use QOM [*] syntax for DR >> connectors", the indexes were small integers: >> >> (qemu) info qom-tree >> /machine (pseries-2.4-machine) >> /unattached (container) >> [...] >> /device[5] (spapr-pci-host-bridge) >> /p...@800000020000000.mmio[0] (qemu:memory-region) >> /p...@800000020000000.mmio-alias[0] (qemu:memory-region) >> /p...@800000020000000.io[0] (qemu:memory-region) >> /p...@800000020000000.io-alias[0] (qemu:memory-region) >> /pci.0 (PCI) >> /pci@800000020000000.iommu-root[0] (qemu:memory-region) >> /dr-connector[0] (spapr-dr-connector) >> /dr-connector[1] (spapr-dr-connector) >> /dr-connector[2] (spapr-dr-connector) >> [...] >> >> Since then, they're big ones: >> >> /dr-connector[1073741824] (spapr-dr-connector) >> /dr-connector[1073741825] (spapr-dr-connector) >> /dr-connector[1073741826] (spapr-dr-connector) >> >> The commit message doesn't quite spell out this change, and I'm >> therefore double-checkint it's intentional. Is it? > > Yes, it's intentional. The small integers were arbitrarily allocated > by the QOM magic [*] code, whereas the big integers are actually > meaningful values (essentially the DRC's global ID for the dynamic > reconfiguration hypervisor interfaces).
Good. >> 2. Before commit 6c2f9a1 "qapi: Make output visitor return qnull() >> instead of NULL", qom-get returned {}: >> >> Since then, it returns null: >> >> QMP> { "execute": "qom-get", "arguments": { "path": >> "/machine/unattached/device[5]/dr-connector[1073741950]", "property": "fdt" >> } } >> {"return": null} >> >> Does anyone care? > > Hm, I'm guessing this is a case where fdt is NULL internally. Which I Yes. > think will happen before a device gets hotplugged into the DRC. In > that case null seems more correct to me than {}, since {} would also > be what's shown for a present-but-empty device tree. It was {} in 2.4. Changing it to null so we can distingish "nothing" from "empty" is an incompatible change. May make sense anyway, but I can't judge it. Thanks!