Re: [PATCH] x86/i8259: Work around buggy legacy PIC

Thomas Gleixner
2021-05-14T17:32:59Z

On Fri, May 14 2021 at 13:58, Maximilian Luz wrote:
> On 5/14/21 9:41 PM, Sachi King wrote:
> I'd assume that _some_ sort of interrupt setup is done by the BIOS/UEFI.
> The UEFI on those devices is fairly well-featured, with touch support
> via SPI and all. Furthermore, keyboard (also supported in the device's
> UEFI) is handled via a custom UART protocol. Unless they rely on polling
> for all of that, I believe they'd have to set up some interrupts.

Polling would be truly surprising.

> Although, as you mention later on, that could also be handled via the
> IOAPIC and the PIC is actually not supposed to be used. Maybe some
> legacy component that never got tested and just broke with some new
> hardware/firmware revision without anyone noticing? And since Linux
> still seems to rely on that, we might be the first to notice.

That's a valid assumption. As I said, we can make IOAPIC work even w/o
PIC. I'll have a look how much PIC assumptions are still around.

Thanks,

tglx