Re: [PATCH] mos6522: remove anh register

[Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>]

On 13/12/2019 08:45, Laurent Vivier wrote:

> Le 13/12/2019 à 02:44, David Gibson a écrit :
>> On Thu, Dec 12, 2019 at 08:43:59PM +0100, Laurent Vivier wrote:
>>> Register addr 1 is defined as buffer A with handshake (vBufAH),
>>> register addr 15 is also defined as buffer A without handshake (vBufA).
>>>
>>> Linux kernel has a big "DON'T USE!" next to the register 1 addr
>>> definition (vBufAH), and only uses register 15 (vBufA).
>>>
>>> So remove the definition of 'anh' and use only 'a' (with VIA_REG_ANH and
>>> VIA_REG_A).
>>
>> I'm not actually following the rationale for removing the register.
>> Linux doesn't use it, but if it's part of the real hardware model we
>> should keep it, no?
> 
> It's actually two methods to access the same register (with handshake,
> without handshake).
> 
> In the datashit Register 15 is described as "Same as register 1 except
> no handshake".

Indeed, certainly my reading of the specification was that it was the same register.
I'd be inclined to add qemu_log() at unimp for the handshake registers so at least we
can easily spot if anything is using them.


ATB,

Mark.