[syslinux] INT22h/000Dh

[Geert Stappers]

On Wed, Sep 05, 2012 at 10:43:44AM +0200, Piotr Romaniuk wrote:
> On 09/04/2012 03:12 PM, Sebastian Herbszt wrote:
> >Piotr Romaniuk wrote:
> >>
> >>Why this function is disabled?
> >
> >It was likely an oversight in commit
> >1656aefeb6b7195db38d25065137c4f37655f33a [1]:
> >
> >COMBOOT interface to the new shuffler; resurrect comapi_chainboot as
> >that functionality is still potentially relevant.
> >
> >[1] http://git.kernel.org/?p=boot/syslinux/syslinux.git;a=commit;h=1656aefeb6b7195db38d25065137c4f37655f33a
> >
> 
> I added proper entry in vector table (i.e. comapi_chainboot), but
> after I call int22h/000Dh it hangs and does not start my code. Am I
> doing something wrong in setup of this interrupt arguments?
> 
>     com32sys_t input_regs, output_regs;
>     input_regs.eax.l=0xd;
>     input_regs.edx.l=0x0;
>     input_regs.edi.l=OFFS(buffer);
>     input_regs.ecx.l=512;
>     input_regs.ebx.l=0x80;
>     input_regs.esi.l=0x0;
>     input_regs.ds=0;
>     input_regs.es=0;
> 
>     __com32.cs_intcall(0x22, &input_regs, &output_regs);
> 
> The buffer contained simple code, just to signal if it is executed on GPIO:
>     buffer:
>         cli

Why this "clear interrupt"?


>         mov  $GPIO_PORT, dx
>         mov  $GPIO_VALUE, al
>         out  al, (dx)

Those are byte wide actions.

What else is connected to the General Purpose Input/Output pins?

What was the previous value of the GPIO register?
In other words: How is ensured that something new is written to "output"?

>     L:  jmp L

That matches 'it hangs'

> 
> Regards
> Piotr Romaniuk
> 
> PS
> I run this on Atom E640.
> 

And most likely there are more factors that effect "is my code executed?"

My advice is to go to something that works and the make small (very small) steps
to what you want. Keep in mind that if it is easy, every could do it.

And a plea: allow people to read in the discussion order.
So please, reply below the previous text.


Groeten
Geert Stappers
-- 
> And is there a policy on top-posting vs. bottom-posting?
Yes.