RE: [PATCH 3/3] mptsas: add SMP passthrough support via bsg

[FUJITA Tomonori <tomof@acm.org>]

From: FUJITA Tomonori <tomof@acm.org>
Subject: RE: [PATCH 3/3] mptsas: add SMP passthrough support via bsg
Date: Fri, 27 Jul 2007 02:09:05 +0900

> Use-space applications can put four memory addresses in the bsg (sg
> v4) interface: request, response, dout_xferp, and din_xferp.
> 
> For scsi commands, we use:
> 
> request -> pointer to a scsi command (cmdp in sgv3)
> response -> pointer to a sense buffer (sbp in sgv3)
> dout_xferp -> pointer to out data
> din_xferp -> pointer to in data
> 
> For smp request/response, we use:
> 
> request -> not used
> response -> not used
> dout_xferp -> pointer to a smp request frame
> din_xferp -> pointer to a smp response frame
> 
> 
> So we could use response field to send vendor's unique response to
> user space.
> 
> bsg wrongly assues the response field is used for sense buffer so the
> maxium length is SCSI_SENSE_BUFFERSIZE, 96 bytes. I think that it's a
> bit small for mpt's unique response. But, I'll fix the length
> limitation bug soon.

Oops, 96 bytes is large enough for mpt's unique response. Right?