[linux-lvm] Re: [RFLART] kdev_t in ioctls

[Andries.Brouwer at cwi.nl]

    On Mon, 14 Jan 2002, Christoph Hellwig wrote:
    >
    > I know - still it makes Linus' suggestion not work on ~90% of the
    > systems.

    It doesn't matter if user-land compilation breaks. As long as old binaries
    work (and they will), we're fine.

    User-land was _already_ broken. By virtue of using a type that it should
    NOT have used.

    If you want to use __kernel_dev_t, go ahead.

            Linus

Yes. As everyone knows, one should not use kernel includes.
On the other hand, having local copies of everything is also
a bad habit, to be avoided when possible.
With Linux it is generally impossible to avoid going to local
copies, but so far losetup survived with the construction

% cat loop.h
#include <linux/posix_types.h>
#undef dev_t
#define dev_t __kernel_dev_t
#include <linux/loop.h>
#undef dev_t
%

Yecch.

(This is terribly ugly, but the alternative may be even worse:
lots of #ifdef's testing architecture etc.)

It is a pity that dev_t, a type that is not used anywhere in the
kernel except at the interface with user space, is a different
type from what user space uses.

Andries