On Tue March 12 2013 07:56:25 Hans Verkuil wrote:
> Hi Sylwester,
>
> On Wed January 23 2013 23:21:57 Sylwester Nawrocki wrote:
> > This patch adds a helper function that allows to modify range,
> > i.e. minimum, maximum, step and default value of a v4l2 control,
> > after the control has been created and initialized. This is helpful
> > in situations when range of a control depends on user configurable
> > parameters, e.g. camera sensor absolute exposure time depending on
> > an output image resolution and frame rate.
> >
> > v4l2_ctrl_modify_range() function allows to modify range of an
> > INTEGER, BOOL, MENU, INTEGER_MENU and BITMASK type controls.
> >
> > Based on a patch from Hans Verkuil http://patchwork.linuxtv.org/patch/8654.
> >
> > Signed-off-by: Sylwester Nawrocki <sylvester.nawro...@gmail.com>
> > Acked-by: Hans Verkuil <hans.verk...@cisco.com>
>
> I've been playing around with this a bit, using this vivi patch:
>
> diff --git a/drivers/media/platform/vivi.c b/drivers/media/platform/vivi.c
> index c46d2e8..85bc314 100644
> --- a/drivers/media/platform/vivi.c
> +++ b/drivers/media/platform/vivi.c
> @@ -1093,6 +1093,15 @@ static int vidioc_s_input(struct file *file, void
> *priv, unsigned int i)
> return 0;
>
> dev->input = i;
> + /*
> + * Modify the brightness range depending on the input.
> + * This makes it easy to use vivi to test if applications can
> + * handle control range modifications and is also how this is
> + * typically used in practice as different inputs may be hooked
> + * up to different receivers with different control ranges.
> + */
> + v4l2_ctrl_modify_range(dev->brightness,
> + 128 * i, 255 + 128 * i, 1, 127 + 128 * i);
> precalculate_bars(dev);
> precalculate_line(dev);
> return 0;
>
> And it made me wonder if it wouldn't be more sensible if modify_range would
> also update the current value to the new default value?
Actually, thinking about it some more, I believe that modify_range should
actually include the new control value as argument. That way the caller can
decide what to do: use the current value (which then might be clamped), use
the default_value or use a remembered previous value.
If you agree with this, then I'll make a patch for it. I just need to know
what the only user of this call (ov9650.c) should do. I suspect it should
use the default value as the new value, but I'm not certain.
Regards,
Hans
> You get weird effects otherwise where the new value is clamped to either
> the minimum or maximum value if the current value falls outside the new
> range.
>
> Regards,
>
> Hans
>
> PS: qv4l2 has been updated to support range update events.
>
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