[OpenBIOS] [commit] r969 - in trunk/openbios-devel/arch: ppc/qemu ppc64/qemu

[Andreas Färber]

Am 30.11.2010 um 21:41 schrieb Mark Cave-Ayland:

> Andreas Färber wrote:
>
>> I noticed that Haiku uses the set-callback ciface method shortly  
>> before, but it appears that we only save the callback-function in  
>> forth/system/ciface.fs and - according to grep - never use it  
>> elsewhere.
>> Shouldn't every ofmem function check if we have a non-zero callback- 
>> function (how? Cf. below) and then call that instead?
>> variable callback-function
>> : set-callback ( newfunc -- oldfunc )
>>  callback-function @
>>  swap
>>  callback-function !
>> ;
>
> AIUI the callback function provides a way for open firmware to call  
> a function within the client image, e.g. allow a Forth function to  
> invoke a "named" C function within the kernel image. I don't believe  
> it is related to OFMEM at all.

The callback function apparently provides a way for the OS to take  
over memory management from OpenFirmware. Thus the relation to ofmem.

http://dev.haiku-os.org/browser/haiku/trunk/src/system/boot/platform/openfirmware/arch/ppc/mmu.cpp?rev=39430#L636

Haiku sets up a new page table based on the one from OpenFirmware,  
calls set-callback and expects to be asked for future memory  
allocations etc.

Andreas