linux-kernel - Re: Disk geometry from /sys

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Message-ID: <38b2ab8a0804101223r7f072f39r2b69b79637a6c928@mail.gmail.com>
Date:	Thu, 10 Apr 2008 21:23:32 +0200
From:	"Francis Moreau" <francis.moro@...il.com>
To:	"Lennart Sorensen" <lsorense@...lub.uwaterloo.ca>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Disk geometry from /sys

Hello,

On Wed, Apr 9, 2008 at 11:28 PM, Lennart Sorensen
<lsorense@...lub.uwaterloo.ca> wrote:
>  Many compact flash cards will report 16 heads, and 16 or 32 sectors
>  per track.  Compact flash can of course connect as an IDE drive, so they
>  are worth supporting (I keep trying to get the grub guys to accept my
>  patch to fix their code that also assumed all disks have 63 sectors per
>  track if they use LBA, but which is false since compact flash also
>  supports LBA even with smaller sizes).
>

Ok so assuming 255 heads seems not to be a good idea.

>  Simplest way to find out what geometry a disk pretents to have is to ask
>  fdisk,

or to create a new entry in /sys:

/sys/block/sda/geometry/heads

?

> and since the only use for the information is when creating
>  partitions, then fdisk's opinion is really all that seems to matter.  Of
>  course partitions can start and end anywhere so the total size is
>  actually all that really matters.
>

I'm not sure about that. Some bootloaders have constraint on the start
and end of a partition. It assume they're aligned on a cylinder size
boundary. I got this warning from sfdisk(8).

Thanks
-- 
Francis
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