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Date: Thu, 17 Mar 2016 16:33:42 -0400
Message-ID: <CAF6AEGvQa8SOWCtoEfcFAxz6MQ0Nqc-ktqNCdfJU-32-m-mCEQ@mail.gmail.com>
Subject: Re: [PATCH v9 2/3] kernel.h: add to_user_ptr()
From: Rob Clark <robdclark@gmail.com>
To: Joe Perches <joe@perches.com>
Cc: Gustavo Padovan <gustavo@padovan.org>,
        Gustavo Padovan <gustavo.padovan@collabora.co.uk>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        devel@driverdev.osuosl.org,
        "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>,
        Daniel Stone <daniels@collabora.com>,
        =?UTF-8?B?QXJ2ZSBIasO4bm5ldsOlZw==?= <arve@android.com>,
        Riley Andrews <riandrews@android.com>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        Greg Hackmann <ghackmann@google.com>,
        John Harrison <John.C.Harrison@intel.com>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel.vetter@intel.com>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
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On Thu, Mar 17, 2016 at 4:22 PM, Joe Perches <joe@perches.com> wrote:
> On Thu, 2016-03-17 at 15:43 -0300, Gustavo Padovan wrote:
>> 2016-03-17 Gustavo Padovan <gustavo.padovan@collabora.co.uk>:
>> > 2016-03-17 Joe Perches <joe@perches.com>:
>> > > On Thu, 2016-03-17 at 14:30 -0300, Gustavo Padovan wrote:
>> > > >
>> > > > This function had copies in 3 different files. Unify them in
>> > > > kernel.h.
>> > > This is only used by gpu/drm.
>> > >
>> > > I think this is a poor name for a generic function
>> > > that would be in kernel.h.
>> > >
>> > > Isn't there an include file in linux/drm that's
>> > > appropriate for this.  Maybe drmP.h
>> > >
>> > > Maybe prefix this function name with drm_ too.
>> > No, the next patch adds a user to drivers/staging (which will be moved
>> > to drivers/dma-buf) soon. Maybe move to a different header in
>> > include/linux/? not sure which one.
>> >
>> > >
>> > > Also, there's this that might conflict:
>> > >
>> > > arch/powerpc/kernel/signal_32.c:#define to_user_ptr(p)          ptr_to_compat(p)
>> > > arch/powerpc/kernel/signal_32.c:#define to_user_ptr(p)          ((unsigned long)(p))
>> > Right, I'll figure out how to replace these two too.
>> The powerpc to_user_ptr has a different meaning from the one I'm adding
>> in this patch. I propose we just rename powerpc's to_user_ptr to
>> __to_user_ptr and leave the rest as is.
>
> I think that's not a good idea, and you should really check
> this concept with the powerpc folk (added to to:s and cc:ed)
>
> If it were really added, then the function meaning is incorrect.
>
> This is taking a u64, casting that to (unsigned long/uint_ptr_t),
> then converting that to a user pointer.
>
> Does that naming and use make sense on x86-32 or arm32?
>

fwiw Gustavo's version of to_user_ptr() is in use on arm32 and arm64..
Not entirely sure what doesn't make sense about it

BR,
-R