[Qemu-devel] Re: [PATCH 2/3] pci: introduce a parser for fw device path to pci device

[Isaku Yamahata <yamahata@valinux.co.jp>]

On Wed, Dec 22, 2010 at 02:03:55PM +0200, Michael S. Tsirkin wrote:
> On Wed, Dec 22, 2010 at 08:36:40PM +0900, Isaku Yamahata wrote:
> > On Wed, Dec 22, 2010 at 01:04:43PM +0200, Michael S. Tsirkin wrote:
> > > On Wed, Dec 22, 2010 at 07:54:49PM +0900, Isaku Yamahata wrote:
> > > > Introduce a function to parse fw device path to pci device.
> > > > the format is
> > > > /pci@{<ioport>, <mmio>}/[<fw_name>]@<slot>,<func>/.../[<fw_name>]@<slot>,<func>
> > > > 
> > > > <ioport> = "i"<ioport addr in hex>
> > > > <mmio> = <mmio addr in hex>
> > > > <slot> = slot number in hex
> > > > <func> = func number in hex
> > > > 
> > > > Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
> > > 
> > > What concerns me the most here is the use of io addresses,
> > > not sure it's the right thing for the command interface.
> > >
> > > Why do we need to support full path at all?  Can we use the id of the
> > > parent bus for this?  Supplying a bus id for the device seems like a
> > > natural way to describe a tree, with minimal need for parsing.
> > 
> > The ids of most devices are set NULL currently. So the id is useless
> > right now unfortunately.
> 
> It's up to the user to assign ids. If one doesn't one won't be able
> to activate hotplug/aer, which does not seem like a serious limitation.
> 
> > Maybe how to assign ids to all of qdevs
> > systematically would be difficult.
> 
> I don't think it's urgent. No id -> can't use some of the
> functionality. No big deal IMO.

Hmm, it's big deal for me.
How about trying id first, if failed, then trying fw device path
as fall back?

> 
> > To be honest, I don't have strong opinion for format of pci topology.
> > So far we discussed the following candidates.
> > what format do you prefer?
> > 
> > - domain:<bus>:<slot>.<func>
> >   guest assigns bus number, so this can't be used for qemu internal use.
> > - domain:00:<slot>.<func>:...:<slot>.<func>
> > - fw device path
> > - id
> >   Unfortunately id is NULL for most devices right now. So id doesn't work.
> > - any other?
> > 
> > thanks,
> > -- 
> > yamahata
> 

-- 
yamahata