Re: RFC: disk geometry via sysfs

[Matt Domsch]

On Wed, Feb 15, 2006 at 04:06:55PM +0000, Alan Cox wrote:
> On Mer, 2006-02-15 at 10:20 -0500, Phillip Susi wrote:
> > I thought that C/H/S addressing was purely a function of int 13, not the 
> > hardware interface?  If it is a function of some older hardware 
> > interfaces, then we are still talking about two different, and likely 
> > incompatible geometries:  the one the disk reports, and the one the bios 
> > reports.  The values in the MBR must be the values the bios reports. 
> 
> We have at least three
> 
> Disk reported C/H/S
> BIOS reported C/H/S (hda/hdb only)
> Actual C/H/S (if it exists)
> Partition table C/H/S
> 
> A partitioning tool needs to know
> 	Disk reported C/H/S
> 	Partition table C/H/S
> 	Preferably BIOS reported C/H/S if there is one
> 
> The partition table C/H/S is on disk so trivial
> The disk reported ones are in the identify block so could be pulled via
> 	/proc and sysfs
> The BIOS one is PC specific low memory poking around

On i386 and x86_64, the edd module reports the 2 types of C/H/S values
as BIOS knows them, in /sys/firmware/edd/int13_dev*/

legacy_max_cylinder, legacy_max_head, and legacy_max_sectors_per_track
are int13 AH=08h values.

default_cylinders, default_heads, and default_sectors_per_track are
int13 AH=48h values.

Files not in that directory mean the value reported by BIOS was zero.

-- 
Matt Domsch
Software Architect
Dell Linux Solutions linux.dell.com & www.dell.com/linux
Linux on Dell mailing lists @ http://lists.us.dell.com
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