On Tue, 6 Jun 2023 at 13:39, Philippe Mathieu-Daudé <phi...@linaro.org> wrote: > > Hi Peter, > > On 6/6/23 12:46, Peter Maydell wrote: > > QEMU allows qemu_irq lines to transfer arbitrary integers. However > > the convention is that for a simple IRQ line the values transferred > > are always 0 and 1. The A10 SD controller device instead assumes a > > 0-vs-non-0 convention, which happens to work with the interrupt > > controller it is wired up to. > > > > Coerce the value to boolean to follow our usual convention. > > I remember once wanting to convert qemu_set_irq() to take a boolean > argument but someone said using integer was more useful because ...? > I searched a bit but can't find that in my mail archives, maybe this > was on IRC. Any clue? (I find simpler to use a boolean rather than > having a convention of using integers restricted to [0, 1] range).
We have a lot of use cases where we just want to transfer a boolean value between two devices. We have a few use cases where we want to transfer an arbitrary integer across the channel between two devices. (For instance hw/intc/etraxfs_pic.c:pic_update() sends a vector number to the CPU via a qemu_irq -- see commit f4f643882d9dc467.) At the moment we use qemu_irq() for both. In theory we could construct a parallel set of machinery for wiring up and setting values for the "want an integer" case and restrict qemu_irq() to bool only, but the lazy path is to use the same function for both. (If we had machinery that made it easy to construct arbitrary strongly-typed signal connections, that might perhaps be ideal. But it's probably not very easy especially in C.) thanks -- PMM
