Am 09.06.2012 03:53, schrieb Peter Crosthwaite: > On Fri, Jun 8, 2012 at 7:45 PM, Andreas Färber <afaer...@suse.de> wrote: >> 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. >> > > How stable is this branch? It seems like I should use it as the > development point. Is the merge immenent. If the merge is delayed, can > I at least rely on the fundamental APIs define here (around links and > stuff) no changing?
At this point we're pretty close to merging (hopefully next week) so I would advise against basing new work on that branch. Just be prepared to rebase onto the "qdev: Convert busses to QEMU Object Model" patch, i.e. BusInfo gets replaced by TypeInfo and creation uses TYPE_FOO. >> As Paul has already mentioned, the concept of tree-structured qdev >> busses is deprecated by QOM in favor of link<> properties. > > Ive had a brief look at the refactorings on qom-next, I notice that > busses are now just children of the parent object TYPE_BUS. > Essentially for point-to-point links this means that link itself has a > QOM object. So for finer clarification, for new busses should or > should I not have an object (whether it inheritTYPE_BUS or some other > parent) for the link itself? Or should The master device interface > directly with its slave? Im thinking the latter, no need for an object > for a trivial point-to-point link. No bus expert myself, deferring to Anthony and Paolo. > Heres what i'm thinking now. each device will > > Inherit from SYSBUS > implement interface AXI_STREAM_SLAVE > have a link property "axi_stream_connected_slave" > > AXI_STREAM_SLAVE has a single function to push data down the link > (what I believe you called DMAPushFn), but I will rename to > axi_stream_push or the like as its not DMA specific. > > Machine model then just sets axi_stream_connected_slave to each other. Doesn't sound wrong so far under the premise of that simplistic modelling approach. Not that I'm specifically advocating this approach. >> 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. > > Im not too worried about that, but Peter and Paul have opened the > discussion. Is the straight up interface on the sysbus device fine for > what im trying to do - or should I have proxy objects for the sake of > consistency? I'm not aware of any use of interfaces in upstream nor of any proxy object. In the end it'll be a compromise between fancy and quick... ;) Regards, Andreas -- SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg