On Wed, 2022-05-04 at 21:58 +0200, Arnd Bergmann wrote: > On Wed, May 4, 2022 at 7:53 PM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > > On Fri, Apr 29, 2022 at 03:50:00PM +0200, Niklas Schnelle wrote: > > > In a future patch HAS_IOPORT=n will result in inb()/outb() and friends > > > not being declared. As ACPI always uses I/O port access we simply depend > > > on HAS_IOPORT. > > > > CONFIG_ACPI depends on ARCH_SUPPORTS_ACPI, which is only set by arm64, > > ia64, and x86, all of which support I/O port access. So does this > > actually solve a problem? I wouldn't think you'd be able to build > > ACPI on s390 even without this patch. > > "ACPI always uses I/O port access" is a pretty broad brush, and it > > would be useful to know specifically what the dependencies are. > > > > Many ACPI hardware accesses use acpi_hw_read()/acpi_hw_write(), which > > use either MMIO or I/O port accesses depending on what the firmware > > told us. > > I think this came from my original prototype of the series where I tested it > out on arm64 with HAS_IOPORT disabled. I would like to hide the definition > of inb()/outb() from include/asm-generic/io.h whenever CONFIG_HAS_IOPORT > is not set, and I was prototyping this on arm64. > > There are uses of inb()/outb() in drivers/acpi/ec.c and drivers/acpi/osl.c, > which in turn are not optional in ACPI, so it seems that those are > required. > > If we want to allow building arm64 without HAS_IOPORT for some reason, > that means either force-disabling ACPI as well, or changin ACPI to not > rely on port I/O. I think it's fine to leave that as a problem for whoever > wants to make HAS_IOPORT optional in the future, and drop the > dependency here. > > Arnd I'll improve the commit message to make the dependency on HAS_IOPORT more clear. I also agree with Arnd that since all architectures where ACPI is useful have I/O ports making it work without I/O port access compiled in is for another day.
