Re: RFC: disk geometry via sysfs

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Seewer Philippe wrote:
Hello all!

I don't want to start another geometry war, but with the introduction of
the general getgeo function by Christoph Hellwig for all disks this
simply would become a matter of extending the basic gendisk block driver.

There are people out there (like me) who need to know about disk
geometry. But since this is clearly post 2.6.16 I prefer to ask here
before writing a patch...

Why do you need to know about geometry? Geometry is a useless fiction that only still exists in PC system BIOS for the sake of backward compatibility with software that was originally designed to operate with MFM and RLL disks that actually used geometric addressing. These days there is no such thing; it's just made up by the bios.
Q1: Yes or No?
If no, the other questions do not apply

Q2: Where under sysfs?
Either do /sys/block/hdx/heads, /sys/block/hdx/sectors, etc. or should
there be a new sub-object like /sys/block/hdx/geometry/heads?

This is not suitable because block devices may not be bios accessible, and thus, nowhere to get any bogus geometry information from. Even if it is, do we really want to be calling the bios to get this information and keep it around?

Q3: Writable?
Under some (weird) circumstances it would actually be quite nice to
overwrite the kernels idea of a disks geometry. This would require a
general function like setgeo. Acceptable?


What for? The only purpose to geometry is bios compatibility. Changing the kernel's copy of the values won't do any good because the bios won't be changed.

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