Re: [PATCH] libata: rewrite SCSI host scheme to be one per ATA host

Jens Axboe
2009-04-23T06:35:42Z

On Wed, Apr 22 2009, Jeff Garzik wrote:
> Jeff Garzik wrote:
>> Currently, libata creates a Scsi_Host per port. This was originally
>> done to leverage SCSI's infrastructure to arbitrate among master/slave
>> devices, but is not needed for most modern SATA controllers. And I
>> _think_ it is not needed for master/slave if done properly, either.
>
> BTW note the above, with regards to the libata SCSI->block conversion.
> libata currently relies on SCSI for some amount of generic device
> arbitration, in several situations (see ->qc_defer,
> SCSI_MLQUEUE_.*_BUSY). libata expects SCSI to be intelligent and not
> starve devices, etc.

Defer looks like internal policy, I don't see that functioning any
different in the block layer. SCSI_MLQUEUE_*_BUSY in SCSI is primarily
using the block layer functionality of BLKPREP_DEFER to begin with, so I
think we're pretty close to providing all that already.

--
Jens Axboe