> A "fake PCI"? Strange. It'd make more sense to stick things > onto some bus that's a more direct match. And to make all > those platforms represent IOIF the same way ... reading between > the lines, I suspect you had multiple Linux teams at work, who > didn't cooperate as closely as might have been desirable!
Multiple companies actually :-) But the situation is more complicated than that... The Cell's IOIF itself is just a point-to-point interface to a southbridge. What's in that bridge (and what type of backbone bus is in there) is a different matter... But yes, the IBM blades generally represent all the devices into the "spider" southbridge (or toshiba scc) as pseudo-PCI device. The illusion is maintained by the firmware (which has calls for config space accesses on those machines) so it's pretty much transparent to the OS. In addition, I think the spider chip was actually designed with that in mind as it does have some pseudo-PCI config space registers for internal devices iirc. The Toshiba Celleb and PS3 platforms and does things differently though. Celleb has a pseudo-PCI thingy but the illusion is maintained by the kernel and it might be changed into a simple of_platform (device-tree probed platform bus) and the PS3 has other differences related to Sony Hypervisor which means it needs to use a special bus type to get things like DMA mapping etc... right. > In most cases, the advice is to use "platform_bus", but there can > be cases where a new bus abstraction is appropriate. We try to use of_platform instead (which is similar but linked to the Open Firmware device-tree). In the case of PS3 though, due to various hypervisor funkyness (that, among others, result into tricks in the way DMA mapping is handled), it should really be a special bus type. > It'd be advantageous to (re)use the same driver glue. If it > weren't for the fact that each chip/system vendor ends up with > minor differences related to system integration, we could make > do with a lot fewer "ohci-XXX.c" bus glue components. But > having two (or three) for Cell seems excessive, especially > if they're all going to the same IOIF ohci controller... Actually the same OCHI inside of the southbridge, IOIF itself has little to do with that. The problem is essentially 3 completely different environments (2 different hypervisors for Sony & Toshiba and a firmware that exposes everything as a pseudo-PCI bus for IBM). Ben. ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
