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Date: Thu, 15 Oct 2009 11:22:40 -0400
From: Jeff Garzik <jeff@garzik.org>
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To: Alan Cox <alan@lxorguk.ukuu.org.uk>
CC: Thomas Gleixner <tglx@linutronix.de>, LKML <linux-kernel@vger.kernel.org>,
       Arnd Bergmann <arnd@arndb.de>, Ingo Molnar <mingo@elte.hu>,
       Peter Zijlstra <peterz@infradead.org>,
       Frederic Weisbecker <fweisbec@gmail.com>
Subject: Re: [RFC] Remove or convert empty ioctls ?
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On 10/15/2009 11:01 AM, Alan Cox wrote:
>> "no particular value" is highly subjective, and I think unprovable,
>> without an exhaustive survey of userland programs interacting with
>> kernel drivers.  Userland programs often interact with a -class- of
>> drivers, expecting predictable behavior from a DoThisThing ioctl, with
>> EINVAL or "other weird error code" returned intentionally.
>>
>> Changing the return codes seems quite unwise.
>
> We've changed lots of them to -ENOTTY over the past few years, nobody has
> even noticed (you included ;))
>
> SuS says an unknown ioctl code returns -ENOTTY.

These are not unknown ioctls; they are ioctls that the driver author 
close to implement rather than the default (ENOTTY).

	Jeff