Re: [PATCH 1/1] scsi: retrieve cache mode using ATA_16 if normal routine fails

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Wed, 2011-12-14 at 09:14 +0530, Amit Sahrawat wrote:
> Just to add a thought - this issues is not related with ATA, this is
> primarily related with HDD's with a USB interface i.e., SCSI <-> USB.
> And, when I check my kernel config, CONFIG_ATA is not selected,
> libata-scsi - this gets compiled only in case CONFIG_ATA is on.
> Are these two things inter-related?

OK, so what you're telling us is that you're trying to correct a
deficiency in a SATL inside a USB device?  The device itself is ATA but
it doesn't use our libata connectors.

I think in that case, the best way forwards is a mini-SATL correction
layer within USB storage.  USB storage is certainly the place to
black/white list whether this should be done.  ATA_16 is a bit of a
dangerous command to be throwing around because it's known to crash
various USB devices (and some old SCSI ones might even choke on it).

depending on how big this SATL ends up being we should consider whether
it should share processing with the libata SATL.  If it's just a single
mode sense, my instinct is that it's probably OK to implement separately
(however, you need to use the libata headers ... no duplication of
libata opcodes and status defines like you had in the original SCSI
patch).  If there are more commands to correct on the way, it might be
better as shared code.

James