Re: [PATCH v4 02/20] nubus-device: expose separate super slot memory region

[Mark Cave-Ayland]

On 20/09/2021 20:54, Laurent Vivier wrote:

> Le 17/09/2021 à 09:50, Mark Cave-Ayland a écrit :
> > According to "Designing Cards and Drivers for the Macintosh Family" each 
> > physical
> > nubus slot can access 2 separate address ranges: a super slot memory region 
> > which
> > is 256MB and a standard slot memory region which is 16MB.
> >
> > Currently a Nubus device uses the physical slot number to determine whether it 
> > is
> > using a standard slot memory region or a super slot memory region rather than
> > exposing both memory regions for use as required.
> >
> > Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> > Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> > ---
> >   hw/nubus/nubus-device.c  | 36 ++++++++++++++++++------------------
> >   include/hw/nubus/nubus.h |  1 +
> >   2 files changed, 19 insertions(+), 18 deletions(-)
> >
> > diff --git a/hw/nubus/nubus-device.c b/hw/nubus/nubus-device.c
> > index be01269563..36203848e5 100644
> > --- a/hw/nubus/nubus-device.c
> > +++ b/hw/nubus/nubus-device.c
> > @@ -168,26 +168,26 @@ static void nubus_device_realize(DeviceState *dev, Error 
> > **errp)
> >       }
> >   
> >       nd->slot = nubus->current_slot++;
> > -    name = g_strdup_printf("nubus-slot-%d", nd->slot);
> > -
> > -    if (nd->slot < NUBUS_FIRST_SLOT) {
> > -        /* Super */
> > -        slot_offset = (nd->slot - 6) * NUBUS_SUPER_SLOT_SIZE;
> > -
> > -        memory_region_init(&nd->slot_mem, OBJECT(dev), name,
> > -                           NUBUS_SUPER_SLOT_SIZE);
> > -        memory_region_add_subregion(&nubus->super_slot_io, slot_offset,
> > -                                    &nd->slot_mem);
> > -    } else {
> > -        /* Normal */
> > -        slot_offset = nd->slot * NUBUS_SLOT_SIZE;
> > -
> > -        memory_region_init(&nd->slot_mem, OBJECT(dev), name, NUBUS_SLOT_SIZE);
> > -        memory_region_add_subregion(&nubus->slot_io, slot_offset,
> > -                                    &nd->slot_mem);
> > -    }
> >   
> > +    /* Super */
> > +    slot_offset = (nd->slot - 6) * NUBUS_SUPER_SLOT_SIZE;
> > +
>
> Is it possible to remove this patch?
>
> The "(nd->slot - 6)" looks weird and it is removed in patch 20.

This is another place where I decided to keep the existing logic as-is and then make 
the change to remove the -6 offset later on in patch 12 ("nubus: move nubus to its 
own 32-bit address space").

Certainly the existing offset is wrong, but given that there are currently no devices 
that use the super slot then I will bring the change to remove the offset forward to 
this patch in v5.

> If not:
>
> Reviewed-by: Laurent Vivier <laurent@vivier.eu>
>
> Thanks,
> Laurent


ATB,

Mark.