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From: Markus Armbruster <armbru@redhat.com>
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Date: Wed, 20 Aug 2014 16:57:27 +0200
In-Reply-To: <53F4A082.7090103@redhat.com> (Paolo Bonzini's message of "Wed,
	20 Aug 2014 15:20:02 +0200")
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Subject: Re: [Qemu-devel] [PATCH 2/3] ioh3420: Provide a unique bus name and
	an interrupt mapping function
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Marcel Apfelbaum <marcel.a@redhat.com>, Alexey Kardashevskiy <aik@ozlabs.ru>, Juan Quintela <quintela@redhat.com>, Knut Omang <knut.omang@oracle.com>, qemu-devel@nongnu.org, Gonglei <arei.gonglei@huawei.com>, "Michael S. Tsirkin" <mst@redhat.com>, Igor Mammedov <imammedo@redhat.com>

Paolo Bonzini <pbonzini@redhat.com> writes:

> Il 20/08/2014 13:36, Michael S. Tsirkin ha scritto:
>> 
>> For pci bridges, unless you set bus_name, bus name will
>> match device itself. See this code:
>> 
>>      * If we don't specify the name, the bus will be addressed as
>>      * <id>.0, where id is the device id.
>>      * Since PCI Bridge devices have a single bus each, we don't need
>>      * the index:
>>      * let users address the bus using the device name.
>>      */
>>     if (!br->bus_name && dev->qdev.id && *dev->qdev.id) {
>>             br->bus_name = dev->qdev.id;
>>     }
>
> Is libvirt using this rule?  If not, I'd rather slash it since the
> <id>.0 name is shared with all other buses and not PCI-bridge-specific.

br->bus_name is null unless pci_bridge_map_irq() set it.  Only caller
for ioh3420 is ioh3420_init(), and that's dead code.  Therefore,
br->bus_name is null here.

Libvirt always sets a device ID.  Slashing this this special case would
change the bus name from ID.0 to just ID.  That'll break libvirt, as far
as I can tell from its source.

Sad.