On Sunday, June 05, 2011 13:55:30 Sakari Ailus wrote:
> On Thu, May 26, 2011 at 04:12:47PM +0900, Kim, HeungJun wrote:
> > >> +
> > >> + struct v4l2_ctrl_handler handle;
> > >> + /* Autoexposure/exposure control cluster */
> > >> + struct {
> > >> + struct v4l2_ctrl *autoexposure;
> > >> + struct v4l2_ctrl *exposure;
> > >> + };
> > >
> > > Would it be different without the anonymous struct?
> > These two v4l2_ctrl is clustered. So, anonymous struct should be used
> > for v4l2_ctrl_cluster().
>
> It makes no difference in how the pointers are arranged in the memory.
The reason I use an anonymous struct for control clusters is that they
nicely highlight that these two pointers belong together.
You don't need to do this, of course, but in that case you have to clearly
group such pointers using comment(s). Alternatively, you can use a pointer
array, but that's a pain in the ass to use in practice.
So the sole purpose of the anonymous struct is to visually group the pointers
without making it harder to access them.
It is debatable whether it is needed if you have only one cluster. But when
you have more than one cluster this approach is very effective.
Regards,
Hans
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