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Re: [PATCH v2 10/12] mac_via: make SCSI_DATA (DRQ) bit live rather than


From: Philippe Mathieu-Daudé
Subject: Re: [PATCH v2 10/12] mac_via: make SCSI_DATA (DRQ) bit live rather than latched
Date: Thu, 24 Feb 2022 15:00:36 +0100
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.6.1

On 24/2/22 12:59, Mark Cave-Ayland wrote:
The VIA2 on the Q800 machine is not a separate chip as in older Macs but instead
is integrated into the on-board logic. From analysing the SCSI routines in the
MacOS toolbox ROM (and to a lesser extent NetBSD and Linux) the expectation 
seems
to be that the SCSI_DATA (DRQ) bit is live on the Q800 and not latched.

Fortunately we can use the recently introduced mos6522 last_irq_levels variable
which tracks the edge-triggered state to return the SCSI_DATA (DRQ) bit live to
the guest OS.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
---
  hw/misc/mac_via.c | 17 ++++++++++++++++-
  1 file changed, 16 insertions(+), 1 deletion(-)

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>



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