[PATCH v5 18/39] [media] v4l: subdev: Add function to validate frame interval

Sakari Ailus sakari.ailus at iki.fi
Sat Mar 11 05:41:19 PST 2017

Hi Steve,

On Thu, Mar 09, 2017 at 08:52:58PM -0800, Steve Longerbeam wrote:
> If the pads on both sides of a link specify a frame interval, then
> those frame intervals should match. Create the exported function
> v4l2_subdev_link_validate_frame_interval() to verify this. This
> function can be called in a subdevice's media_entity_operations
> or v4l2_subdev_pad_ops link_validate callbacks.
> Signed-off-by: Steve Longerbeam <steve_longerbeam at mentor.com>

If your only goal is to configure frame dropping on a sub-device, I suggest
to implement s_frame_interval() on the pads of that sub-device only. The
frames are then dropped according to the configured frame rates between the
sink and source pads. Say, configuring sink for 1/30 s and source 1/15 would
drop half of the incoming frames.

Considering that supporting specific frame interval on most sub-devices adds
no value or is not the interface through which it the frame rate configured,
I think it is overkill to change the link validation to expect otherwise.

Kind regards,

Sakari Ailus
e-mail: sakari.ailus at iki.fi	XMPP: sailus at retiisi.org.uk

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