Re: [Qemu-devel] [PATCH] initialize unit id of IDE bus

[Markus Armbruster]

Gleb Natapov <address@hidden> writes:

> On Mon, Oct 25, 2010 at 06:22:12PM +0200, Markus Armbruster wrote:
>> Gleb Natapov <address@hidden> writes:
>> 
>> > On Mon, Oct 25, 2010 at 04:29:35PM +0200, Markus Armbruster wrote:
>> >> Gleb Natapov <address@hidden> writes:
>> >> 
>> >> > Without this patch both buses on PIIX3_IDE device have the same unit id.
>> >> 
>> >> Are you sure that's wrong?
>> >> 
>> > So how do I know which bus is it on PIIX3_IDE?
>> [...]
>> 
>> Let me try to explain the IDE pointer thicket.
>> 
>> piix3-ide provides two IDE buses.  pci_piix_ide_initfn() stores them in
>> PCIIDEState member IDEBus bus[2].  Technically redundant, because qdev
>> stores child buses in dev.qdev.child_bus.
>> 
>> IDEBus points back: qbus.parent.
>> 
>> Up to two IDE devices can sit on each IDE bus.  The first one uses
>> IDEBus members master and ifs[0], the second one uses slave and ifs[1].
>> 
>> ifs[i].bus points back to the IDE bus.
>> 
>> {master,slave}.qdev.parent_bus point back to the IDE bus.
>> 
>> Say you got an IDEDevice and want to know which to which of the two
>> buses it's connected.  Let's call it d.
>> 
>> d->qdev.parent_bus is the BusState.
>> 
>> Upcast to IDEBus: b = DO_UPCAST(IDEBus, qbus, d->qdev.parent_bus).
>> 
>> b->qbus.parent is the IDE controller.
>> 
>> Upcast to PCIIDEState: c = DO_UPCAST(PCIIDEState, dev, n->qbus.parent);
>> 
>> If c->bus[0] == b, it's on the first bus.
>> 
>> Else it must be on the second bus, i.e. c->bus[1] == b.
>> 
>> Hope I didn't screw this up too badly.
> Will check tomorrow if this works, but why not have simple property on
> IDEBus that says which one is it?

Because nobody has needed it so far?

Does the bus care whether it's first or second?

>                                   BTW what -device magic should I use to
> create secondary disk on second IDE bus?

Try -device ide-drive,bus=ide.1,unit=1,drive=...