[OpenBIOS] Tokenizer (fcode-utils 1.0.2) support for 64-bit constants.

[Asif Haswarey]

After the responses to my post about the utility of 64-bit
constant support and talking to David Paktor (the one who
did a major re-implementation of (de)toke), I am not sure
if it's worthwhile. 64-bit constants is not currently clearly
supported in the OpenFirmware std.
I originally used 64-bit constants in my fcode as part of a
data-structure scheme. I then modified portions of the toke
source to support 64-bit constants and did very minimal tests.
It seems to produce the same image as Sun Microsystem's tokenizer
would produce.
For now I simply re-implemented my fcode's data-structure scheme
using 32-bit constants and it's fine.
My major partially related concern is the limited token-number size as
defined in the OpenFirmware spec, although, toke does allow a
way to "re-use" token numbers by placing a tokenizer-directive
in strategic points in the fcode.
I original data-structure design scheme was to minimize the use of
token numbers.

Thanks very much for your responses, everyone!

-Asif

-----Original Message-----
From: openbios-bounces at openbios.org [mailto:openbios-bounces at openbios.org] On Behalf Of Segher Boessenkool
Sent: Saturday, April 18, 2009 3:52 AM
To: The OpenBIOS Mailinglist
Subject: Re: [OpenBIOS] Tokenizer (fcode-utils 1.0.2) support for 64-bit constants.

> I think 64bit constants won't work on architectures with a 32bit  
> cell size, so FCode using them will not be platform independent.

An FCode driver can check for 64-bit support at runtime and skip over
some code if it's not there.

> Can you give a usage example of 64bit constants? I would assume  
> it's not BARs as those can be read from PCI config space?

Some devices have 64-bit MMIO registers that should not be accessed as
(pairs of) 32-bit registers.

> What's the expected output of the tokenizer? put two 32bit  
> constants on the stack, shift one by 32bit and OR them?

32-bit-const-1 32-bit-const-2 lxjoin

Note that 32-bit consts are sign-extended on 64-bit systems.

> To be sure, we could add a command line option for enabling 64bit  
> constants support and print a warning or an error in case it is not  
> set. Does that sound reasonable?

Sure.  Error please.


Segher


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