2011/4/1 Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>: > If you have discoverable hardware, use it. > > But by "discoverable hardware" I mean something like PCI config > cycles. IOW, real hardware features. The ARM AMBA architecture actually has such a thing, or a little of it, found in drivers/amba/bus.c. Basically it requires you to get the physical address and size of each peripheral, then at offset -0x10 from the end address (usually at even 4K pages), if you find the magic number 0xB105F00D (ARM has a sense of humour, obviously) you can find something alike the PCI IDs at offset -0x20, manufacturer ID, version number and revision of the hardware. It isn't very hard to imagine that mechanism providing IRQ numbers or DMA channel allocation and other such data so it becomes more plug'n'play-ish. If the hardware had a list of device physical whereabouts in a specific location too, the system would be quite self-describing. Not as sexy as the separate PCI configuration space though, it's just hardcoded in along with the device I/O pages. Apparently ARM pushed this in their few initial cells and manufacturers are free to reuse this system for their silicon. ST Microelectronics for example actually use it to a larger extent. But since it was not mandatory and there was no clear way on how to register magic numbers with this system (like the PCI-SIG), it simply failed. Silicon foundries didn't care or even know about it, neglecting to put this 0xB105F00D in place. IMO the world would have been much better off if ARM mandated that all vendors *must* use this scheme for their hardware blocks if they are to license the AMBA bus incarnations, but they don't. Maybe the ARM guys on the list has some background on this? Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
