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

From: Marek Szyprowski
Date: Tue Feb 21 2017 - 09:55:18 EST

Dear All,

On 2017-02-21 15:37, Marek Szyprowski wrote:
Hi Christian,

On 2017-02-21 14:59, Christian KÃnig 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

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

Best regards
Marek Szyprowski, PhD
Samsung R&D Institute Poland