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Re: [Qemu-devel] [RFC] Plan for moving forward with QOM

From: Peter Maydell
Subject: Re: [Qemu-devel] [RFC] Plan for moving forward with QOM
Date: Fri, 16 Sep 2011 18:47:56 +0100

On 16 September 2011 17:33, Gleb Natapov <address@hidden> wrote:
> On Thu, Sep 15, 2011 at 09:45:33PM +0100, Peter Maydell wrote:
>> On 15 September 2011 21:29, Gleb Natapov <address@hidden> wrote:
>> > 16650A is not a device. ISA card it resides on is a device.
>> The 16550A is an encapsulated set of functionality with some
>> well defined interfaces ("I provide a set of memory mapped
>> registers", "I have an output gpio line (irq)"), which we
>> need to be able to compose into other things (lots of models
>> use a 16550A one way or another, not just the ISA serial card),
>> connect up (ie connect that irq to an appropriate interrupt
>> controller, map the registers in system memory or under ISA
>> or whatever), and configure (eg specify the backend chardev).
>> I don't think there's any difference at all between that
>> and (say) the NE2000 PCI model, which also is encapsulated
>> functionality with well defined interfaces that we need to
>> be able to compose and connect and configure. We should be
>> using the same implementation and abstractions for both
>> cases.
> IDE is another such device (it was ISA later converted to PCI).
> As far as I understand your view of UART is the same as mine.
> It is not a whole device, but only a part of it.

If we have the same view of the UART then one of us is rather
misunderstanding the other (could be me).

I don't care whether you apply the label "device" to the
UART, but I definitely want it to be exactly the same kind
of QEMU "object", in terms of how you implement it and use it,
as a PCI NE2000 model or an ISA serial card or an ARM-Cortex-A8
CPU model or a "vexpress-a9" board model.

As it happens, personally I think "device" is a pretty
reasonable label to use for all these things, since we're going
to use it anyway for the QEMU objects which happen to correspond
to ISA cards or PCI cards or whatever.

-- PMM

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