[743] in linux-scsi channel archive
Re: Boot Kernels
daemon@ATHENA.MIT.EDU (Eric Youngdale)
Wed Nov 1 23:43:00 1995
From: "Eric Youngdale" <eric@aib.com>
Date: Wed, 1 Nov 1995 09:13:09 -0500
In-Reply-To: "Leonard N. Zubkoff" <lnz@dandelion.com>
"Boot Kernels" (Oct 31, 4:25pm)
To: "Leonard N. Zubkoff" <lnz@dandelion.com>, linux-scsi@vger.rutgers.edu
On Oct 31, 4:25pm, Leonard N. Zubkoff wrote:
> Subject: Boot Kernels
> As far as I understand it, it's not possible to provide any kernel command
> line options when booting off floppy to install a system. If I am
> incorrect in this, someone please correct me.
>
> The issue I'm looking to address is the following. By default, my new
> BusLogic driver will have it's performance features enabled, such as
tagged > queuing and multiple outstanding commands per logical unit, but
command
> line options will allow control over these features as necessary to
> compensate for buggy hardware or poorly configured SCSI systems. However,
> it would be nice to also give folks with buggy or poorly configured
> hardware the possibility of installing successfully. Once their system is
> installed, they can use kernel command line options to turn off tagged
> queuing if necessary, or to reduce the concurrency,
> but I don't see a way to do this during installation from boot floppy.
The approach that had been informally discussed earlier is to
use the /proc/scsi/ interface to turn on/off features like tagged queueing
and some of these other features. The idea is that the driver would come
up with many of these things turned off, and the sysmgr could enable them
if they appear to work reliably. The procedure would be to write some kind
of ascii string to the device like:
echo "tagged_queue=enable" > /proc/scsi/aha1542/0
which would be meaningless in this case, since the 1542 does not support
tagged queueing, but you get the idea. This is something that could easily
be integrated into rc scripts.
> Since a large number of users will never build custom kernels, I am
unwilling
> to cripple the standard driver to support broken hardware, nor do I really
> expect builders of installation boot kernels to build them specially. One
> possibility I have considered is to disable performance features whenever
> booting an installation kernel (i.e. root = floppy and ramdisk exists),
but
> this really feels like a kludge.
No, it is definitely work considering and discussing. The solution
you outlined above does seem like a kluge to me too.
Another solution would be one boot option like "wussy-scsi" that
disables some of the things like tagged queueing and so forth to increase
the chances of a successful boot. The idea is that there would be only one
such switch that could be tested by all of the low-level drivers.
-Eric
--
"The woods are lovely, dark and deep. But I have promises to keep,
And lines to code before I sleep, And lines to code before I sleep."
