Messages in this thread | | | Date | Wed, 23 Apr 2008 09:02:33 +0200 | From | "Francis Moreau" <> | Subject | Re: Disk geometry from /sys |
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On Wed, Apr 23, 2008 at 12:44 AM, Mark Lord <lkml@rtr.ca> wrote: > > On Fri, Apr 18, 2008 at 3:22 PM, Mark Lord <lkml@rtr.ca> wrote: > > > > > That can sound a bit misleading. The complete story, for ATA/SATA > drives, > > > is that the disk has two geometries: an internal physical one, with a > > > fixed number of heads and cylinders, but variable sectors/track > > > (which normally varies by cylinder zone). > > > > > > Software *never* sees or knows about that geometry, so ignore it. > > > > > > The second geometry, is the one that the drive reports to software > > > as its "native" geometry. This is what you see from "hdparm -I" > > > and friends, and this geometry is what has to be used by software > > > when using cylinder/head/sector (CHS) addressing for I/O operations. > > > The hardware interface has a limit of 4-bits for the head value, > > > so the maximum number of heads can never be more than 16. > > > > > > Nobody uses CHS addressing for I/O operations, at least not on > > > any hardware newer than at least ten years old, so this geometry > > > is also unimportant for most uses. > > > > > > > > > > Is it because IDE drives support several IO operation modes ? > > > .. > > The earliest IDE drives for Compaq used only CHS sector addressing mode. > > Within four years, though, all new drives had support for the more sensible > linear block addressing (LBA) mode, as well. >
My last question I promise ;)
If I'd like to take a look in the kernel code to see where the kernel translates an offset provided by sys_read into a LBA or CHS address, where should I go ? drivers/block ?
Thanks ! -- Francis
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