From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [PATCH] libata: rewrite SCSI host scheme to be one per ATA host Date: Wed, 22 Apr 2009 05:23:49 -0400 Message-ID: <49EEE225.3010700@garzik.org> References: <20090422090929.GA14928@havoc.gtf.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20090422090929.GA14928@havoc.gtf.org> Sender: linux-kernel-owner@vger.kernel.org To: linux-ide@vger.kernel.org, linux-scsi@vger.kernel.org Cc: LKML , Jens Axboe , Tejun Heo List-Id: linux-ide@vger.kernel.org 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. > I was able to successfully boot the following patch on > AHCI/x86-64/Fedora. > > It may work with other controllers -- TRY AT YOUR OWN RISK. It will > probably fail for master/slave configurations, and SAS & PMP also > need looking at. It yielded this lsscsi output on my AHCI box: > > [0:0:0:0] disk ATA ST3500320AS SD15 /dev/sda > [0:2:0:0] disk ATA G.SKILL 128GB SS 02.1 /dev/sdb > [0:5:0:0] cd/dvd PIONEER BD-ROM BDC-202 1.04 /dev/sr0 For comparison, here is unmodified 2.6.30-rc3: [jgarzik@bd ~]$ lsscsi [0:0:0:0] disk ATA ST3500320AS SD15 /dev/sda [2:0:0:0] disk ATA G.SKILL 128GB SS 02.1 /dev/sdb [5:0:0:0] cd/dvd PIONEER BD-ROM BDC-202 1.04 /dev/sr0