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SubjectRe: [patch 6/7] um: Convert mmapper to unlocked_ioctl
On Thu, 15 Oct 2009 15:00:34 +0200
Arnd Bergmann <arndbergmann@googlemail.com> wrote:

> On Thursday 15 October 2009, Thomas Gleixner wrote:
> > The ioctl is empty and needs no serialization. We might remove it
> > completely but that would change the return value from -ENOIOCTLCMD to
> > -ENOTTY.
> >
> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> > Cc: Jeff Dike <jdike@addtoit.com>
>
> This one is tricky if you want to get it right according to the
> book. ENOIOCTLCMD is never a valid return code for user space,
> but sys_ioctl passes it down anyway.
>
> However, returning -ENOIOCTLCMD from an *unlocked_ioctl* function
> automatically gets turned into -EINVAL. It does this to allow
> the same functions to be used for unlocked_ioctl and compat_ioctl.
> In effect, this patch is functionally identical to removing the
> ioctl function, which I think is what should be done here.

That is wrong.

SuS requires an unknown ioctl code returns -ENOTTY. If the code is
currently remapping it to EINVAL then it wants fixing.


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