Re: [Qemu-devel] [RFC] QOMification of AXI stream

[Andreas Färber]

Am 08.06.2012 06:23, schrieb Peter Crosthwaite:
> Each of the two core has three interfaces (+interrupt pins):
> 
> 1: Sysbus attachment for device control
> 2: AXI stream TX link
> 3: AXI stream RX link
[...]
> struct XilinxDMAConnection {
>     void *dma;
>     void *client;
> 
>     DMAPushFn to_dma;
>     DMAPushFn to_client;
> };
> 
> So what im proposing is AXI stream is implemented as a unidirectional
> point to point bus. The xilinx ethernet system would consist of two of
> these buses one for tx, one for rx.
[...]
> A: Make AXI_STREAM_SLAVE an interface (not a sub-class of DEVICE). Its
> kind of annoying though if someone in the future whats the create a
> device thats only and axi stream slave, as they would have to
> explicitly inherit from DEVICE as well.
> 
> or
> 
> B: Have the slave attachment be a device within a device. Hard part is
> getting an accessor so machine models can retrieve the slave
> attachment and hook it up.

If you dive into busses, note that Anthony has refactored QBus on
qom-next branch.

As Paul has already mentioned, the concept of tree-structured qdev
busses is deprecated by QOM in favor of link<> properties.

SysBus is also in the process of being deprecated, and Anthony is
working on Pin objects for simple qemu_irq-style messaging.

What you could try as option C today is deriving a type from SysBus with
one added DMAPushFn and a link<> property of that type for
unidirectional connection and form circular links for RX and TX...
That would of course limit the number of channels to one. Otherwise you
need a dedicated child<> object, of which a device can have multiple.

Regards,
Andreas

-- 
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg