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

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Date:   Thu, 23 Feb 2017 12:07:12 +0530
From:   Sumit Semwal <sumit.semwal@...aro.org>
To:     Daniel Vetter <daniel@...ll.ch>
Cc:     Christian König <deathsimple@...afone.de>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        "linaro-mm-sig@...ts.linaro.org" <linaro-mm-sig@...ts.linaro.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>
Subject: Re: [PATCH] dma-buf: add support for compat ioctl

Hi Marek,

On 23 February 2017 at 00:37, Daniel Vetter <daniel@...ll.ch> wrote:
> 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>.
>

Thanks much for spotting this!

> 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.
>
Daniel, Christian,

I saw this just now, so if Christian hasn't already pulled it into
drm-misc-next-fixes, I'll give it a stab.

> Thanks, Daniel
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
> _______________________________________________
> dri-devel mailing list
> dri-devel@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

Best,
Sumit.

-- 
Thanks and regards,

Sumit Semwal
Linaro Mobile Group - Kernel Team Lead
Linaro.org │ Open source software for ARM SoCs

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