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SubjectRe: [PATCH 2/5] drivers/media/video/uvc: Use DIV_ROUND_CLOSEST
On Sat, 1 Aug 2009, Laurent Pinchart wrote:

> On Saturday 01 August 2009 21:49:04 Julia Lawall wrote:
> > From: Julia Lawall <julia@diku.dk>
> >
> > The kernel.h macro DIV_ROUND_CLOSEST performs the computation (x + d/2)/d
> > but is perhaps more readable.
> >
> > The semantic patch that makes this change is as follows:
> > (http://www.emn.fr/x-info/coccinelle/)
> >
> > // <smpl>
> > @haskernel@
> > @@
> >
> > #include <linux/kernel.h>
> >
> > @depends on haskernel@
> > expression x,__divisor;
> > @@
> >
> > - (((x) + ((__divisor) / 2)) / (__divisor))
> > + DIV_ROUND_CLOSEST(x,__divisor)
> > // </smpl>
> >
> > Signed-off-by: Julia Lawall <julia@diku.dk>
> >
> > ---
> > drivers/media/video/uvc/uvc_v4l2.c | 2 +-
> > 1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/drivers/media/video/uvc/uvc_v4l2.c
> > b/drivers/media/video/uvc/uvc_v4l2.c index 87cb9cc..6edaaf6 100644
> > --- a/drivers/media/video/uvc/uvc_v4l2.c
> > +++ b/drivers/media/video/uvc/uvc_v4l2.c
> > @@ -95,7 +95,7 @@ static __u32 uvc_try_frame_interval(struct uvc_frame
> > *frame, __u32 interval) const __u32 max = frame->dwFrameInterval[1];
> > const __u32 step = frame->dwFrameInterval[2];
> >
> > - interval = min + (interval - min + step/2) / step * step;
> > + interval = min + DIV_ROUND_CLOSEST(interval-min, step) * step;
> > if (interval > max)
> > interval = max;
> > }
>
> The purpose of the above code is to clamp the interval value to the [min, max]
> range at round it to the closest multiple of step. Other drivers might need
> similar code. Do you think it might be useful to introduce a clamp_step macro
> for this ?

I tried searching for the following:

@@
expression interval, min, max, step, E;
@@

* interval = min + (interval - min + step/2) / step * step;
... when != interval = E
* if (interval > max)
{ ...
interval = max;
... }

@@
expression interval, min, max, step, E;
@@

* interval = min + DIV_ROUND_CLOSEST(interval-min, step) * step;
... when != interval = E
* if (interval > max) { ...
interval = max;
... }

and the only occurrence I found was the code above. Perhaps there is some
other way in which the pattern would appear?

julia


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