HDIO_GETGEO vs. BLKGETSIZE

[Andre Hedrick]

If we have a superior answer over the "HDIO_GETBIGGEO" kludge, I am up for
change.  I would ask it to stay until we verify that the newest changes
are what we desire........after that.....rip it......

On Mon, 22 May 2000, Andries Brouwer wrote:

> On Mon, May 22, 2000 at 01:06:17PM +0100, David Woodhouse wrote:
> 
> > Is it permitted for a driver to returns CHS values for HDIO_GETGEO which, 
> > when multiplied together, don't match the value returned by BLKGETSIZE?
> 
> Yes - HDIO_GETGEO may contain whatever you want.
> A modern fdisk will use the values for heads and sectors/track
> given by HDIO_GETGEO, but ignore the value for cylinders.
> 
> Indeed, since cylinders is a 16-bit field and the number of cylinders
> can be larger than 65535, the value may be truncated, and is to be
> considered worthless.
> 
> Instead, the number of cylinders is computed as BLKGETSIZE/(H*S).
> (Thus, there is no need for a new ioctl HDIO_GETBIGGEO or so.
> I think the code for it should be deleted from the kernel.)
> 
> Andries
> 
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Andre Hedrick
The Linux ATA/IDE guy



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