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List:       openbios
Subject:    [OpenBIOS] Re: [PATCH v3 3/6] Define register access words
From:       BALATON Zoltan <balaton () eik ! bme ! hu>
Date:       2022-10-11 10:43:40
Message-ID: 4eb43c7e-14e6-569c-1e54-8e63c267e13 () eik ! bme ! hu
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On Mon, 10 Oct 2022, Segher Boessenkool wrote:
> Hi!
>
> On Sun, Oct 09, 2022 at 09:41:21PM +0200, BALATON Zoltan wrote:
>> On Sun, 25 Sep 2022, BALATON Zoltan wrote:
>>> Define the r[bwl][!@] register access words as io[bwl][!@] for now.
>>> I'm not sure this is correct.
>
>> https://github.com/aik/SLOF/blob/master/slof/fs/fcode/evaluator.fs#L107
>> https://github.com/aik/SLOF/blob/master/slof/fs/fcode/tokens.fs#L19
>>
>> (If these are FCode tokens I don't get when the big endian versions could
>> be used as these should only be called from FCode so not sure this change
>> of rokens is really necessary and we could just do little endian access in
>> these register access words.)
>
> And the user interface rb@ etc. should use get-token (or equivalent):
>
>
> rb@ (user interface) ( addr -- byte )
> Fetch a byte from device register at addr.
>
> Compilation: ( -- )
> Perform the equivalent of the phrase:
>  h# 230 get-token if execute else compile, then
>
> Interpretation: ( addr -- byte )
> Perform the equivalent of the phrase:
>  h# 230 get-token drop execute
>
> NOTE— A bus device can substitute (see set-token) a bus-specific
> implementation of rb@ for use by its children. This is sometimes
> necessary to correctly implement its semantics with respect to bit-order
> and write-buffer flushing. The given user interface semantics of rb@
> ensure that such substitutions are visible at the user interface level.

OK so what does all that mean? We could do what you say in 
openbios/forth/device/other.fs for r[bwl][!@] words. There are already 
rx[!@] words that seem to do that so I could just copy that with modified 
token numbers for the other words. But where to assign the tokens for PCI 
then? Or is it OK for now to just add little endian versions which should 
work for FCode ROMs and nothing else uses these words otherwise as they 
are currently unimplemented.

Regards,
BALATON Zoltan

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