Alan Cox <alan <at> lxorguk.ukuu.org.uk> writes:

> 
> > So then ap->prd[idx].flags_len gets set to (0x10000 & 0xFFFF) = 0 !
> > So this sg element ends up with a zero length, even though the
> > transfer size should be 64k.
> > 
> > Is this correct behaviour, if not, should it be corrected ?
> 
> The specification says that 0x0000 means 64K. A couple of controllers do
> get this wrong and we did recently add a second sg list builder for those.
> 
> Perhaps a comment or two is in order ?
> -

Thanks - but which specification is this ?

As far as I am aware there is no spec for DMA controllers running ATA.

Since DMA controller details may vary according to hardware, I
would have expected that ata_fill_sg() would be one of the overloadable
function entries with a driver-specific function that knew about
the DMA controller niceties, and how to stuff a sg entry.

Cheers,
MikeW




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