linux-kernel - Re: [patch 6/7] um: Convert mmapper to unlocked

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Date:	Sat, 17 Oct 2009 04:58:10 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Arnd Bergmann <arndbergmann@...glemail.com>
cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jeff Dike <jdike@...toit.com>
Subject: Re: [patch 6/7] um: Convert mmapper to unlocked_ioctl

On Fri, 16 Oct 2009, Arnd Bergmann wrote:

> On Thursday 15 October 2009, Alan Cox wrote:
> > On Thu, 15 Oct 2009 15:00:34 +0200
> > Arnd Bergmann <arndbergmann@...glemail.com> wrote:
> >
> > > 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.
> 
> Right, I forgot about the EINVAL/ENOTTY difference. The code currently
> returns -ENOIOCTLCMD, which is worse. Thomas' patch makes it return
> -EINVAL, which as you said is still wrong. Removing the ioctl function
> will do the right thing and return -ENOTTY, so that should be done
> here in um/mmapper, with an appropriate changelog.
> 
> For the common code in fs/ioctl.c, I think the current behaviour is
> correct. It returns -EINVAL if the driver returns -ENOIOCTLCMD, iow

Only the unlocked_ioctl code path, the locked one returns whatever
crap comes from the ioctl implementation.

> "the request [...] argument is not valid for this device", as specified
> by http://www.opengroup.org/onlinepubs/009695399/functions/ioctl.html.
 
> Drivers returning ENOIOCTLCMD for every request are broken and should
> be changed to have no ioctl function.

Ack.

	tglx
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