HDIO_GETGEO vs. BLKGETSIZE
aeb at veritas.com
Mon May 22 10:17:56 EDT 2000
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
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.)
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