On 2011-06-10 15:10, Peter Maydell wrote: > On 10 June 2011 13:51, Anthony Liguori <aligu...@us.ibm.com> wrote: >> On 06/10/2011 03:13 AM, Markus Armbruster wrote: >>> >>> Jan Kiszka<jan.kis...@siemens.com> writes: >>>> >>>> Resource management, e.g. IRQs. That will be useful for other types of >>>> buses as well. >>> >>> A device should be able to say "I need to be connected to an IRQ line". >>> Feels generic to me. >> >> More specifically, a device has input IRQs. A device has no idea what >> number the IRQ is tied to.
Generally true. Two exceptions still require to make the path explorable / transfer information in the reverse direction: IRQ de-coalescing and physical device assignment. That's something a new generic API should encapsulate so that we can stop peaking into the machine details. >> >> Devices may also have output IRQs. At the qdev layer, we should be able to >> connect an arbitrary output IRQ to an arbitrary input IRQ. > > Actually, devices have input and output I/O signals (GPIOs, if you like). > A subset of these are IRQs. We already have some APIs in QEMU which > claim to be dealing with 'irq's but actually are just for wiring > up generic signals; I'd rather we didn't proliferate that terminology > confusion if possible. (And a single GPIO wire is just one kind of > thing you might want to link between two devices, obviously. MMIO is > another.) > >> So the crux of the problem is that: >> >> -device isa-serial,id=serial,irq=3 >> >> Is very wrong. It ought to look something more like >> >> -device piix3,id=piix3 -device isa-serial,id=serial,irq=piix3.irq[3] > > This makes the wiring of this signal look like a property of the > isa-serial device, which is a bit odd, since it's just as much > a property of the piix3. Actually it's neither, it's a property > of the machine model, and you might actually want a syntax a bit > more like: > > piix3 = piix3(property=value, property=value...); > serial = isa-serial(property=value...); > connect(serial.irq, piix3.irq[3]); In fact, in the ISA case, it is a device property: The device, and only the device decides which IRQ to use - from the bus it is attached to. So attaching an ISA device to the bus of an ISA bridge like the PIIX3 and selecting local IRQ 3 are the steps we can already express today. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux
