Re: Restoring HDIO_GETGEO semantics for 2.6 (was: Re: [RFC] Restoring HDIO_GETGEO semantics)

Bartlomiej Zolnierkiewicz
2004-07-05T18:59:35Z

Andries, the question was "What should we do with HDIO_GETGEO breakage?"
not "Why does somebody need the BIOS geometry?". :-)

We can fix HDIO_GETGEO to behave like in 2.4 or remove it (preferable),
current situation is bad.

On Monday 05 of July 2004 16:00, Andries Brouwer wrote:
> On Mon, Jul 05, 2004 at 03:13:48PM +0200, Bartlomiej Zolnierkiewicz wrote:
> > We can restore ide-geometry.c or try to return values obtained from
> > EDD code through IDE driver. Alternatively we can add new ioctl for
> > start of partition and remove HDIO_GETGEO from IDE driver completely
> > but probably it is too late for this for 2.6 (we should do it early
> > in 2.7 then). Andries?
>
> For Linux purposes geometry is almost irrelevant.
> (But, as I remarked in another letter, some RAIDs need something.)
>
> This means as a first approximation that "geometry" is not a kernel
> business. Certainly the present discussion is not about the ide-driver.
> Indeed, what people want is the geometry that a certain BIOS will assign
> to a disk. That depends on the BIOS, and on whether the user has
> set things up with Normal / Large / LBA in the BIOS setup.
> (In case the disk was left out of the BIOS setup, this particular
> concept of geometry does not exist at all.)
>
> So, the question is whether information from the BIOS can be
> exposed. Well, that is not impossible, and EDD already does this.
>
> Why would people want to know what a BIOS would do?
> So far I have mostly seen two classes of wishes.
> One is to install lots of new Windows systems on blank disks
> - that is done faster and more conveniently from Linux -
> where there is no partition table yet to inspect.
> The other is to create or modify NTFS filesystems.
>
> Such are reasonable wishes, but rather special purpose.
> For the time being I have good hopes that it will turn out
> to be possible to do these things. Maybe using present EDD.
> Maybe by extending EDD a little.
>
> Five years ago I wrote a library that takes collected BIOS info,
> and collected Linux info, and tries to match BIOS disks with
> Linux disks. Of course it is impossible to do this right, but
> one can find heuristics that often work. Such heuristics do not
> belong in the kernel, but a user space application can decide,
> given the known situation, whether a guess is probably right,
> or perhaps consult the user.
>
> I am awaiting the discussion with Szaka.
>
> Andries