Re: Proposals to change the way all drivers work with SCSI commands

[Stefan Richter <stefanr@s5r6.in-berlin.de>]

James Bottomley wrote:
> Right at the moment, we're planning to clean up the way SCSI drivers
> process commands.  The proposals are essentially:
> 
>      1. Get rid of the now unnecessary map_single path (every command is
>         either zero transfer or scatter/gather)
>      2. use accessors to manipulate the SG lists (mainly so that we can
>         alter the implementation without affecting the drivers)

Should be fine with the old and the new SBP-2 driver.

> It strikes me that in all of this, we could also consider doing the DMA
> mapping inside the mid layer (instead of in every driver).  This is
> essentially what libata is already doing ... leading to confusion in
> SCSI drivers that use libata for SATA.
> 
> So what do people think about this?

The old SBP-2 driver needs the virtual addresses of S/G elements if
compiled with a certain config option.  This option is meant for use
with FireWire controllers which do not implement OHCI-1394, or to run
the IEEE 1394 stack in a more secure mode.   However, sbp2 seems to be
broken in multiple ways with this option at the moment, and I don't plan
to fix it anytime soon.

So in short, moving the DMA mapping into mid layer should also be fine
with the old and the new SBP-2 driver.
-- 
Stefan Richter
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