From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [RFC PATCH v1 5/7] media: v4l2: introduce two IOCTLs for face detection Date: Fri, 02 Dec 2011 13:33:36 +0100 Message-ID: <42689146.OPtqLboC2m@wuerfel> References: <1322817178-8931-1-git-send-email-ming.lei@canonical.com> <1322817178-8931-6-git-send-email-ming.lei@canonical.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: <1322817178-8931-6-git-send-email-ming.lei@canonical.com> Sender: linux-kernel-owner@vger.kernel.org To: linux-arm-kernel@lists.infradead.org Cc: Ming Lei , Mauro Carvalho Chehab , Tony Lindgren , Greg KH , linux-kernel@vger.kernel.org, Sylwester Nawrocki , Alan Cox , linux-omap@vger.kernel.org List-Id: linux-omap@vger.kernel.org On Friday 02 December 2011 17:12:56 Ming Lei wrote: > +/** > + * struct v4l2_fd_result - VIDIOC_G_FD_RESULT argument > + * @buf_index: entry, index of v4l2_buffer for face detection > + * @face_cnt: return, how many faces detected from the @buf_index > + * @fd: return, result of faces' detection > + */ > +struct v4l2_fd_result { > + __u32 buf_index; > + __u32 face_cnt; > + __u32 reserved[6]; > + struct v4l2_fd_detection *fd; > +}; This data structure is not 32/64 bit safe: running a 64 bit kernel with 32 bit user space will see an incompatible layout. One way to solve this is to remove the pointer and just start the array directly after the __u32 members. Alternatively, you can use a __u64 to pass the pointer in an integer representation. A nicer interface from the data structure perspective would be to get rid of the array altogether and always return exactly one face. Arnd