[syslinux] Read disk not working in 3.35+
H. Peter Anvin
hpa at zytor.com
Mon Feb 19 20:45:22 PST 2007
H. Peter Anvin wrote:
> Ram Yalamanchili wrote:
>> Thanks for the fix. I'm ok with waiting to 3.40.
>>
>> Another question would be, would you want to provide a library
>> function which can allocate the memory in the fashion 0x19h needs it:
>> aligned and not crossing 64k boundaries?
>>
>> I am not sure if static allocation of a variable and using it's
>> address will work since it might be above the 16bit address range.
>
> Not just might, but *will* be.
>
>> eg: char sectorBuf[64*1024*2] and getting an address within it which
>> is aligning to 64k.
>>
>> If you dont think the lib function is a good idea, what options do i
>> have other than using the bounce buffer?
>
> None. The bounce buffer is actually by definition *all* the memory
> below 1 MB available to the COM32 program.
>
By the way, the best way to use the bounce buffer is really to consider
it local around the intcall: copy your data to the bounce buffer
immediately before invocation, and copy your data from the bounce buffer
immediately after. This is pretty much what the library functions
should do.
-hpa
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