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Date:      Wed, 2 Dec 1998 17:30:35 -0700 (MST)
From:      "Kenneth D. Merry" <ken@plutotech.com>
To:        aa8vb@pagesz.net (Randall Hopper)
Cc:        Wayne.Baety@kadena.af.mil, freebsd-current@FreeBSD.ORG, freebsd-questions@FreeBSD.ORG
Subject:   Re: CAM
Message-ID:  <199812030030.RAA28810@panzer.plutotech.com>
In-Reply-To: <19981202191134.B868@pagesz.net> from Randall Hopper at "Dec 2, 98 07:11:34 pm"

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Randall Hopper wrote...
> Baety Wayne Amn 18CS/SCBD:
>  |Where's documentation on properly configuring a kernel for use with this new
>  |CAM SCSI subsystem.  I have a Mylex DAC960PL (uses Symbios 53C720SE
>  |controller) and am wondering how to enable it in the kernel.
> 
> I asked for that a week or so ago, and didn't get any response.  So I don't
> know if there are any such docs.  For example, CAM is in 3.0-RELEASE, and
> there's really nothing on it in the handbook or FAQ.  There is cam(3),
> pass(4), and xpt(4), but that isn't really a how-to.

I sent a response to the original poster on the SCSI list.  There are quite
a few CAM man pages, actually.  Some other interesting ones:

scsi(4)
cam_cdbparse(3)
camcontrol(8)

> My limited understanding is that if you're running a CAM-enabled kernel,
> CAM is just "there".  My original pre-CAM SCSI-related kernel lines flew
> with a CAM kernel with no change except "sd" disks are now "da" disks:
> 
>     controller   ncr0
>     controller   scbus0 at ncr0                     # Single bus device
>     disk         cd0 at scbus0 target 0 unit 0      # SCSI CD-ROM
>     device       sa0 at scbus0 target 4 unit 0      # SCSI tapes
>     disk         da0 at scbus0 target 5 unit 0      # da0 = ZIP Drive

And 'st' is now 'sa'.

> There's this new concept of a pass-through device (/dev/pass*) which I'm
> not too sure about; these are doled out to detected SCSI devices.  And
> there's a TLI device (/dev/xpt*) which I think is allocated 1 per bus.

TLI?  What's that?  There's one transport layer device per transport layer,
not per bus.  Right now, there's only one transport layer.

Depending on how (or if) ATAPI support is integrated into CAM, there may
be another transport layer instance eventually.

> In addition to the above lines, I also added a wired-down pass0 so I
> could configure SANE to find my scanner consistently.  I also wired down my
> CDRW, though I don't know if that's necessary or not:
> 
>     device       pass0 at scbus0 target 6 unit 0    # CAM passthrough = Scanner
>     device       pass1 at scbus0 target 0 unit 0    # RICOH MP6200S CDRW

You shouldn't need to wire down your CDRW at least.  I'm not sure exactly
how Corey did the SANE port, so that may be necessary.  If you configure
the pt driver in your kernel, you should be able to specify the passthrough
driver that way as well.

You should be able to access the CDRW via cdrecord by specifying its bus,
target and lun.

> SCSI bus rescans and lists are much simpler with CAM (from a user's
> perpective at least):
> 
>     camcontrol rescan 0
>     camcontrol devlist
> 
> That's about all I know at this point.

Well, for the average user, most of the documentation available now is
probably sufficient.  There are docs describing:

 - all CAM userland utilities (just camcontrol(8) right now)
 - most CAM userland programming interfaces (except CCB types, see below)
 - how to configure your kernel for CAM (scsi(4) and LINT)
 - how to configure debugging printfs (camcontrol(8) and scsi(4))
 - basic man pages on all the peripheral drivers
 - basic man pages for most of the controller drivers

The main pieces of documentation that are missing now are:

 - all of the CCB types, what they do, etc.
 - the internal structure of the transport layer
 - "HBA" driver to transport layer interface
 - peripheral driver to transport layer interface

Ken
-- 
Kenneth Merry
ken@plutotech.com

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