[SeaBIOS] [RFC PATCH] Add support for Intel Quark UART.

David Woodhouse dwmw2 at infradead.org
Wed May 28 22:06:42 CEST 2014

On Wed, 2014-05-28 at 15:36 -0400, Kevin O'Connor wrote:
> On Mon, May 19, 2014 at 07:49:47PM +0100, David Woodhouse wrote:
> > On Mon, 2014-05-19 at 13:42 -0400, Kevin O'Connor wrote:
> > > I don't see any reference to "int 15h, ax=0xd042" as a standard.  So,
> > > maybe the author of the above text also wrote their own EFI module
> > > which used that magic value?
> > 
> > Well, the INT 15h call would still be on the BIOS side; that doesn't
> > sound like an EFI thing at all. Perhaps that's a special-case hack to
> > make their platform *trigger* the SMM entry, which then gets handled by
> > the EFI code?
> FYI, I just stumbled upon this definition in the std/LegacyBios.h efi
> header file:
> ///
> /// SMM_FUNCTION Function constants.
> ///@{
> #define INT15_D042        0x0000
> [...]
> -Kevin

I've been reading through the EDK2 SMM stuff, and invoking SMM functions
from seems to involve putting parameters into a buffer at a certainly
location, then triggering an SMI. On the EFI side there's obviously a
function you can invoke to *do* it, but we could do it directly.

To make use of it from SeaBIOS-CSM, I think we'd just need to pass in
the location of that buffer. There's space in the EFI_COMPATIBILITY16
table for "IBV-specific" information.


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