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

[David Miller <davem@davemloft.net>]

From: James Bottomley <James.Bottomley@SteelEye.com>
Date: Fri, 11 May 2007 13:33:41 -0500

> 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)
> 
> 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?

This would require platforms to handle all of their bus types
behind the generic dma_*() and that's isn't true everywhere yet.

For example, SBUS still requires explicitly using sbus_map_sg() etc.

I plan to fix that of course, but we're not there now.