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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Sat, 4 May 2019 10:35:02 -0400
Message-ID: <CAK8P3a2EKXrg4amHDi5zVvOQ8AM+u6EAhBc=T8Hk_tU20xSV4w@mail.gmail.com>
Subject: Re: [PATCH V3 04/12] misc: xilinx_sdfec: Add open, close and ioctl
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     Dragan Cvetic <dragan.cvetic@xilinx.com>,
        Michal Simek <michal.simek@xilinx.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        DTML <devicetree@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Derek Kiernan <derek.kiernan@xilinx.com>
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On Thu, May 2, 2019 at 1:23 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Sat, Apr 27, 2019 at 11:04:58PM +0100, Dragan Cvetic wrote:
> > Add char device interface per DT node present and support
> > file operations:
> > - open(),
> > - close(),
> > - unlocked_ioctl(),
> > - compat_ioctl().
>
> Why do you need compat_ioctl() at all?  Any "new" driver should never
> need it.  Just create your structures properly.

The function he added was the version that is needed when the structures
are compatible. I submitted a series to add a generic 'compat_ptr_ioctl'
implementation that would save a few lines here doing the same thing,
but it's not merged yet.

Generally speaking, every driver that has a .ioctl() function should also
have a .compat_ioctl(), and ideally it should be exactly this trivial
version.

        Arnd