On Wed, Aug 21, 2013 at 05:57:07PM +0200, Linus Walleij wrote: > - The I2C address is specified in "reg" - maybe ACPI have > some other way to assign I2C addresses to I2C devices? > In any case, it *must* reference the parent I2C controller, > here that is done implicitly by placing this DT node inside > the I2C controllers DT node. That's fine. You put the child device inside the I2C contorller's scope, which can be done from a separate ACPI table if you want. The address can be provided via _ADR(). > - Then it is using a GPIO line as interrupt, and specify that > this shall be configured as a falling edge IRQ. ACPI 5 permits this. > - It then tells the interrupt controller parent. So it needs > to have a reference to whatever interrupt chip device > will handle that IRQ. By interrupt controller, do you mean the GPIO controller? ACPI GPIO definitions include the parent device. > - Further it *is* an interrupt controller, so devices connected > to the GPIO lines may generate IRQs and then this > device should service them. Is it possible that the devices > connected to this expander in turn use ACPI to describe > themselves? Then we need a reference in the other > direction. I think that's also doable. > - Further it is a wakeup source, so each IRQ it provides > on its GPIO lines can be set as a wakeup. I wonder how > this plays with D-states and ACPI. That's fine. GPIO lines can be described as causing ACPI events and then that simply referenced as a wakeup event. > I did present the above as an extreme example, but if we > start to combine DT and ACPI we have to have that kind of > hardware in mind. GPIO expanders with IRQs and all are > maybe rare on desktops and laptops but very common on > embedded systems. Yeah, describing complicated device topology isn't really the problem I think we'll end up facing - it's the wider range of device configuration data that worries me. -- Matthew Garrett | mjg59@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
