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Message-ID: <38b2ab8a0804221316o7cab5641q16814849a1099b9a@mail.gmail.com> Date: Tue, 22 Apr 2008 22:16:01 +0200 From: "Francis Moreau" <francis.moro@...il.com> To: "Mark Lord" <lkml@....ca> Cc: "Seewer Philippe" <philippe.seewer@....ch>, linux-kernel@...r.kernel.org Subject: Re: Disk geometry from /sys Hello Mark On Fri, Apr 18, 2008 at 3:22 PM, Mark Lord <lkml@....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 ? thanks -- Francis -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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