Re: bug in setup.S / IDE code

Andre M. Hedrick (hedrick@Astro.Dyer.Vanderbilt.Edu)
Thu, 21 Jan 1999 09:17:56 -0600 (CST)


This has puzzled me also, due to booting order events and I do not have an
answer.

We first INIT all IDE-code.
Then we do the SCSI-code.
Next we register SCSI-disks.
Finally we register IDE-disks.

In the meantime, we later poke the partition table.

I may not have the exact order, but it goes something like above.

On Thu, 21 Jan 1999 Andries.Brouwer@cwi.nl wrote:

> After installing a new large IDE disk in some machine, I found
> to my surprise that Linux detects the geometry as 1020/200/62
> while the BIOS had 16383/16/63, as was to be expected for
> a large disk. The CMOS has the right values.
>
> What goes wrong?
>
> Well, the IDE code gets the BIOS information from setup.S,
> and the code there gets hd0 and hd1 data via the INT 41 and INT 46
> addresses. But who says that hd0 and hd1 are IDE disks?
>
> This machine (Pentium with Award BIOS) has both IDE and SCSI
> disks, and boots from SCSI. And indeed, /dev/sda has geometry
> 1020/200/62.
>
> Thus, the IDE driver mistook "first disk" for "first IDE disk".
>
> Clearly, we would like to know which disks the BIOS called
> "first" and "second" disk. I guess that the first disk is
> the one on which the BIOS starts the boot loader.
> But the kernel no longer has this information.
> Moreover, maybe it was booted by loadlin or so.
>
> Is there something meaningful the kernel can do?

Nope.......a question of who gets first crack at booting is a major
rehack and a tought one too.

> Or should the user just tell the kernel on the command line:
> "first disk is sda"?
>
> Andries
>
>
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Cheers,
Andre Hedrick
The (NEW) Linux IDE guy
The APC UPS Specialist for Linux

http://www.dyer.vanderbilt.edu/server/udma/
http://www.dyer.vanderbilt.edu/server/apcupsd/apcupsd-3.5.2.bin.tar.gz

You just need a bigger hammer, or learn how to swing the one you have better.
(C) me.....

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