RE: Kernel newbie finds "infelicity", if not bug, in IDE[-PROBE]. C ?

Guest section DW (dwguest@win.tue.nl)
Wed, 21 Apr 1999 18:27:51 +0200 (MET DST)


<quote from other thread "Wierd IDE configuration">
>> (aeb)It is well documented how to avoid having problems.
>> (aeb)(For example, boot with hdc=c,h,s, or give fdisk an explicit
geometry.)
</quote from other thread "Wierd IDE configuration">

One thing I'm quite certain of, is that Joe Public is not about to put Linux
on his machine if he needs to get CHS values right in the boot command line.
We appear to have two categories of people who are likely to hit this
problem:
- anyone with IDE drives, SCSI drives, and a SCSI BIOS
- anyone with hard drives hda and hdc; for example, if hdb is a CD.
That's a small, but not trivial, percentage of the user population.

You don't have to convince me. I agree entirely.

Is this important? No, I don't think so. Linux will run fine without
such boot parameters, only fdisk and LILO will give strange warnings.
People read a FAQ or ask around in a newsgroup, and presto - all works.
[For example, the fact that accessing a FAT filesystem may destroy it
is important. Compared to that this geometry stuff is a microscopic flaw.]

Is this annoying? Yes, very. Especially since better code is available
already.

>(aeb)And calling INT 13h AH=8 does not necessarily give you IDE
information.
It does, however, give us all the disks which the BIOS knows about, which I
presume ought to include the IDE drives, plus any SCSI drives which the BIOS
can handle.

Not necessarily. For example, a good way to avoid all problems with
BIOS translations is to take the disks out of the BIOS setup.
With the setup set to None, the BIOS will not report anything and
Linux will just use the values from Identify.
This works fine, unless you also want to use other operating systems
that use the BIOS, or unless you want to boot from one of these disks.

I suppose we then hit the question of when the IDE/SCSI distinction should
be made. I wonder if there's enough information to do this around at
setup.S time; I suspect it will involve the IDE driver asking the BIOS and
*somehow* reconciling the BIOS drive list with the do_identify()-type data.

I do not know of any method that would do this reliably, except on very
modern BIOSes.

A more fundamental question, perhaps: why do we need BIOS-translated
geometry at all ?

For fdisk and LILO.
Not for Linux.

Andries

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