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

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Date:   Tue, 21 Feb 2017 16:08:25 +0100
From:   Christian König <deathsimple@...afone.de>
To:     Marek Szyprowski <m.szyprowski@...sung.com>,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org
Cc:     linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH] dma-buf: add support for compat ioctl

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>.

Regards,
Christian.

>
> Best regards