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

[Daniela Engert]

Boaz Harrosh wrote:
> On 04/22/2009 12:23 PM, 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.

> > > 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
>
> Could the master/slave be simply solved by emulating a SCSI LUN

Don't forget, there are ATAPI devices (some Sony CD burners and old 
phase-changers come into mind) which *do* have multiple LUNs sitting 
beyond the PATA port. I don't know if libata supports such setups (my 
old OS/2 driver does) but one shouldn't hijack LUNs to emulate targets.

Ciao,
  Dani
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