Re: [hatari-devel] Natfeats doc?

[Eero Tamminen <oak@xxxxxxxxxxxxxx>]

Hi,

On 7.9.2021 18.14, Troed Sångberg wrote:
> On Tue, Sep 7, 2021 at 16:27, Thorsten Otto <admin@xxxxxxxxxxx> wrote:
> > On Dienstag, 7. September 2021 15:50:56 CEST Troed Sångberg wrote:
> >
> > > I don't see "trigger debugger" in the Aranym Natfeats doc)
> >
> > That's because that NatFeat is only implemented by Hatari, but not by Aranym.
> >
> > The principle is the same as with other natfeats:
> >
> > - get the ID of the function, by executing the NATFEAD_ID opcode, passing it "NF_DEBUGGER" as function name. If that opcode does not throw an illegal exception, and D0 after the call contains some other value as zero, the feature is supported.
> >
> > - or in the subfunction number. In your case, the feature does not have any subfunctions.
> >
> > - pass that value to nf_call, along with any arguments (if any)
> >
> > tests/natfeats/natfeats.c in Hatari has some example code, as well as the various nf_*.c files in mintlib.

And there are also examples for doing NF detection
in 3 different assembler dialects:
https://git.tuxfamily.org/hatari/hatari.git/tree/tests/natfeats/

(Example for getting the IDs after NF detection
is just in C, but translating those few lines to
asm is trivial for anybody who actually uses m68k
asm...)


> Thanks.
>
> With assembler developers in mind, I'd like to voice my support for the simple move.b trigger as added by Tat (which is the same as in Steem if I understood things correctly). When doing demo development having to care for changes to registers etc when just wanting to trigger the debugger is very cumbersome.

Is using stack (register) a problem in demos?

After your demo init fetches the relevant NF IDs,
I think invoking e.g. debugger is just:

	pea nf_debugger_id
	bsr _nf_call

Where nf_call is:
-------------------------
; call native feature by its ID
_nf_call:
        dc.w   $7301
        rts
-------------------------

And if you don't want nf_call to branch
elsewhere, you add assembler macro to inline
that functionality... Right?


> I agree about not needing lots of duplicate functionality - so let's remove the already deprecated Xbios call when adding it?
>
> Natfeats is a bit more targeted towards high level development, imho.


	- Eero