On 2011-06-10 15:10, Peter Maydell wrote:
On 10 June 2011 13:51, Anthony Liguori<address@hidden> wrote:
On 06/10/2011 03:13 AM, Markus Armbruster wrote:
Jan Kiszka<address@hidden> 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.