Re: [Qemu-devel] [PATCH 0/2] Add get_dev_path callback to ISA bus.

[Gleb Natapov <gleb@redhat.com>]

On Tue, Oct 26, 2010 at 11:57:53AM +0200, Markus Armbruster wrote:
> Gleb Natapov <gleb@redhat.com> writes:
> 
> > On Mon, Oct 25, 2010 at 07:53:41PM +0200, Markus Armbruster wrote:
> >> Gleb Natapov <gleb@redhat.com> writes:
> >> 
> >> > On Mon, Oct 25, 2010 at 05:10:15PM +0200, Markus Armbruster wrote:
> >> >> Gleb Natapov <gleb@redhat.com> writes:
> >> >> 
> >> >> > PCI bus already has one. For ISA bus this patch series uses device's
> >> >> > ioports to uniquely describe it. For isa-ide, for example, get_dev_path
> >> >> > method returns:
> >> >> > 01f0-01f7,03f6 for first IDE controller
> >> >> > 0170-0177,0376 for second one
> >> >> 
> >> >> Any I/O port used by the device identifies it.  I'd say a common
> >> >> identifier is the "I/O base", the lowest I/O port used.
> >> > So use only first port from the string. More information is better then
> >> > less information. You can always drop information you do not need.
> >> 
> >> I'd prefer canonical bus addresses to be terse.  It's not the place to
> >> give additional information.
> >
> > I'd prefer them to give full info but not more. I don't see why you
> > point is more valid then mine.
> 
> Full information about ISA resources is more than I/O ports, it also
> includes IRQs and DMA channels.
So you are arguing to add more info there? :) Theoretically there is
nothing that prevents ISA devices from sharing IRQ line (existing ISA
devices just not built to do that and nobody produces new once) and
DMA is separate device on ISA bus AFAIK.

> 
> An address is not the place to give full information.  The purpose of an
> address is to name a thing, not to give full information about that
> thing.
> 
Address should contain info that allows to find device easily. If
whoever looking for a device knows only one port device is using he
will not find the device if we'll use different port to name it. May be
not the problem in practice.

> 
> By the way, get_dev_path() really needs a written contract.  Actually,
> all the qdev and qbus callbacks do.
What do you mean by that? It should be stable ABI, is this what you
mean?

--
			Gleb.