Re: [PATCH 1/8] mac_via: update comment for VIA1B_vMystery bit

[Mark Cave-Ayland]

On 15/10/2021 07:14, Laurent Vivier wrote:

> Le 13/10/2021 à 23:21, Mark Cave-Ayland a écrit :
> > According to both Linux and NetBSD, port B bit 6 is used on the Quadra 800 to
> > configure the GLUE logic in A/UX mode. Whilst the name VIA1B_vMystery isn't
> > particularly descriptive, the patch leaves this to ensure that the constants
> > in mac_via.c remain in sync with Linux's mac_via.h.
> >
> > Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> > ---
> >   hw/misc/mac_via.c | 4 ++++
> >   1 file changed, 4 insertions(+)
> >
> > diff --git a/hw/misc/mac_via.c b/hw/misc/mac_via.c
> > index 993bac017d..7a53a8b4c0 100644
> > --- a/hw/misc/mac_via.c
> > +++ b/hw/misc/mac_via.c
> > @@ -130,6 +130,10 @@
> >                                   * On SE/30, vertical sync interrupt enable.
> >                                   * 0=enabled. This vSync interrupt shows up
> >                                   * as a slot $E interrupt.
> > +                                * On Quadra 800 this bit toggles A/UX mode 
> > which
> > +                                * configures the glue logic to deliver some 
> > IRQs
> > +                                * at different levels compared to a classic
> > +                                * Mac.
> >                                   */
> >   #define VIA1B_vADBS2   0x20    /* ADB state input bit 1 (unused on IIfx) */
> >   #define VIA1B_vADBS1   0x10    /* ADB state input bit 0 (unused on IIfx) */
>
> I'm not sure we need to keep in sync a word that neither used by linux or qemu 
> (for now).
>
> Perhaps you can put a word from where it is (NetBSD)?
>
> It seems it's supported by all Quadra, not only Quadra 800 (see NetBSD comment 
> in mac68k/machdep.c
>
> Anyway:
>
> Reviewed-by: Laurent Vivier <laurent@vivier.Eu>

Yeah, it's a hard one: you can see the bit referenced in the via_alt_mapping logic in 
Linux but mac_via.h still shows it as VIA1B_vMystery (and indeed, it seems to have 
different uses on different machines). The thought behind adding the comment was to 
better explain the purpose of VIA1B_vMystery within the series.


ATB,

Mark.