linux-kernel - RE: [Xen-devel] [PATCH 1/3] xen/privcmd: return -ENOSYS for unimplemented IOCTLs

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Message-ID: <1bf3a822caf94d7a9e9afee86d5ec1b5@AMSPEX02CL03.citrite.net>
Date:   Thu, 9 Feb 2017 15:28:54 +0000
From:   Paul Durrant <Paul.Durrant@...rix.com>
To:     'Boris Ostrovsky' <boris.ostrovsky@...cle.com>,
        Jan Beulich <JBeulich@...e.com>
CC:     "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        "Juergen Gross" <JGross@...e.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [Xen-devel] [PATCH 1/3] xen/privcmd: return -ENOSYS for
 unimplemented IOCTLs

> -----Original Message-----
> From: Boris Ostrovsky [mailto:boris.ostrovsky@...cle.com]
> Sent: 09 February 2017 15:26
> To: Jan Beulich <JBeulich@...e.com>; Paul Durrant
> <Paul.Durrant@...rix.com>
> Cc: xen-devel@...ts.xenproject.org; Juergen Gross <JGross@...e.com>;
> linux-kernel@...r.kernel.org
> Subject: Re: [Xen-devel] [PATCH 1/3] xen/privcmd: return -ENOSYS for
> unimplemented IOCTLs
> 
> 
> 
> On 02/09/2017 09:40 AM, Jan Beulich wrote:
> >>>> On 09.02.17 at 15:17, <paul.durrant@...rix.com> wrote:
> >> The code goes so far as to set the default return code to -ENOSYS but
> >> then overrides this to -EINVAL in the switch() statement's default
> >> case.
> >
> > If you already change this, isn't -ENOTTY the traditional way of
> > indicating unsupported ioctls?
> 
> In fact, a while ago David submitted a patch to do just that:
> 
> https://lists.xenproject.org/archives/html/xen-devel/2016-
> 08/msg00744.html
> 
> but it never went anywhere.
> 
> My question is whether anyone might be relying on current error return
> behavior.

I doubt it. It's certainly not a safe thing to do anyway. I'll change to -ENOTTY in v2 of the patch.

  Paul

> 
> 
> -boris