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    SubjectRe: [RFC PATCH v1 5/7] media: v4l2: introduce two IOCTLs for face detection
    From
    Hi,

    On Mon, Dec 5, 2011 at 10:37 PM, Arnd Bergmann <arnd@arndb.de> wrote:
    > 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.

    OK, I opt to use __u64 to pass the user pointer, so how about the blow
    changes on this patch?

    diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
    index 073eb4d..8aeaa1e 100644
    --- a/include/linux/videodev2.h
    +++ b/include/linux/videodev2.h
    @@ -2214,7 +2214,12 @@ struct v4l2_fd_result {
    __u32 buf_index;
    __u32 face_cnt;
    __u32 reserved[6];
    - struct v4l2_fd_detection *fd;
    +
    + /*make 64/32 compatible*/
    + union {
    + struct v4l2_fd_detection *fd;
    + __u64 dummy;
    + };
    };

    /**
    thanks,
    --
    Ming Lei


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