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From: Arnd Bergmann <arnd@arndb.de>
To: Ming Lei <ming.lei@canonical.com>
Subject: Re: [RFC PATCH v1 5/7] media: v4l2: introduce two IOCTLs for face detection
Date: Mon, 5 Dec 2011 14:37:27 +0000
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On Sunday 04 December 2011, Ming Lei wrote:
> >
> > This data structure is not 32/64 bit safe: running a 64 bit kernel with 32 bit
> > user space will see an incompatible layout.
> 
> I agree that this is not 32/64 bit safe, but I understand lib32 can handle
> this correctly, otherwise many 32bit applications can't run on current
> 64bit kernel
> since many kernel structures used by user space contained pointer,
> such as struct v4l2_buffer, struct v4l2_ext_controls in v4l2 ABI.

The other ones you mentioned are handled in the kernel in
drivers/media/video/v4l2-compat-ioctl32.c. For new ioctl commands,
it's better to define the data structure in a compatible way
so you do not need a wrapper like that.

	Arnd