linux-kernel - Re: [PATCH] dma-buf: add support for compat ioctl

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Date:   Wed, 22 Feb 2017 20:07:38 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Christian König <deathsimple@...afone.de>
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        "linaro-mm-sig@...ts.linaro.org" <linaro-mm-sig@...ts.linaro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH] dma-buf: add support for compat ioctl

On Tue, Feb 21, 2017 at 4:08 PM, Christian König
<deathsimple@...afone.de> wrote:
> Am 21.02.2017 um 15:55 schrieb Marek Szyprowski:
>>
>> Dear All,
>>
>> On 2017-02-21 15:37, Marek Szyprowski wrote:
>>>
>>> Hi Christian,
>>>
>>> On 2017-02-21 14:59, Christian König wrote:
>>>>
>>>> Am 21.02.2017 um 14:21 schrieb Marek Szyprowski:
>>>>>
>>>>> Add compat ioctl support to dma-buf. This lets one to use
>>>>> DMA_BUF_IOCTL_SYNC
>>>>> ioctl from 32bit application on 64bit kernel. Data structures for both
>>>>> 32
>>>>> and 64bit modes are same, so there is no need for additional
>>>>> translation
>>>>> layer.
>>>>
>>>>
>>>> Well I might be wrong, but IIRC compat_ioctl was just optional and if
>>>> not specified unlocked_ioctl was called instead.
>>>>
>>>> If that is true your patch wouldn't have any effect at all.
>>>
>>>
>>> Well, then why I got -ENOTTY in the 32bit test app for this ioctl on
>>> 64bit ARM64 kernel without this patch?
>>>
>>
>> I've checked in fs/compat_ioctl.c, I see no fallback in
>> COMPAT_SYSCALL_DEFINE3,
>> so one has to provide compat_ioctl callback to have ioctl working with
>> 32bit
>> apps.
>
>
> Then my memory cheated on me.
>
> In this case the patch is Reviewed-by: Christian König
> <christian.koenig@....com>.

Since you have commit rights for drm-misc, care to push this to
drm-misc-next-fixes pls? Also I think this warrants a cc: stable,
clearly an obvious screw-up in creating this api on our side :( So
feel free to smash my ack on the patch.

Thanks, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch