[libcamera-devel] [RFC PATCH 3/6] libcamera: v4l2_subdevice: Add methods to get/set frame interval

[Laurent Pinchart]

Hi Marian,

Thank you for the patch.

On Tue, Mar 16, 2021 at 04:52:08PM +0100, Marian Cichy wrote:
> Add API-methods to get and set the frame interval on V4L2-subdevices.
> 
> Signed-off-by: Marian Cichy <m.cichy at pengutronix.de>
> ---
>  include/libcamera/internal/v4l2_subdevice.h |  4 ++
>  src/libcamera/v4l2_subdevice.cpp            | 43 +++++++++++++++++++++
>  2 files changed, 47 insertions(+)
> 
> diff --git a/include/libcamera/internal/v4l2_subdevice.h b/include/libcamera/internal/v4l2_subdevice.h
> index d2b9ca55..310746d9 100644
> --- a/include/libcamera/internal/v4l2_subdevice.h
> +++ b/include/libcamera/internal/v4l2_subdevice.h
> @@ -12,6 +12,7 @@
>  #include <vector>
>  
>  #include <libcamera/class.h>
> +#include <libcamera/fraction.h>
>  #include <libcamera/geometry.h>
>  
>  #include "libcamera/internal/formats.h"
> @@ -60,6 +61,9 @@ public:
>  	int setFormat(unsigned int pad, V4L2SubdeviceFormat *format,
>  		      Whence whence = ActiveFormat);
>  
> +	int getFrameInterval(unsigned int pad, Fraction *frameInterval);
> +	int setFrameInterval(unsigned int pad, Fraction *frameInterval);
> +
>  	static std::unique_ptr<V4L2Subdevice>
>  	fromEntityName(const MediaDevice *media, const std::string &entity);
>  
> diff --git a/src/libcamera/v4l2_subdevice.cpp b/src/libcamera/v4l2_subdevice.cpp
> index 721ff5a9..eac2d7d3 100644
> --- a/src/libcamera/v4l2_subdevice.cpp
> +++ b/src/libcamera/v4l2_subdevice.cpp
> @@ -17,6 +17,7 @@
>  #include <linux/media-bus-format.h>
>  #include <linux/v4l2-subdev.h>
>  
> +#include <libcamera/fraction.h>
>  #include <libcamera/geometry.h>
>  
>  #include "libcamera/internal/log.h"
> @@ -440,6 +441,48 @@ int V4L2Subdevice::setFormat(unsigned int pad, V4L2SubdeviceFormat *format,
>  	return 0;
>  }
>  
> +int V4L2Subdevice::getFrameInterval(unsigned int pad, Fraction *frameInterval)
> +{
> +	struct v4l2_subdev_frame_interval subdevFrameInterval = {};
> +	subdevFrameInterval.pad = pad;
> +
> +	int ret = ioctl(VIDIOC_SUBDEV_G_FRAME_INTERVAL, &subdevFrameInterval);

Sensor drivers are supposed to control the frame rate through horizontal
and vertical blanking. Only in very specific cases do we want to use
these ioctls, when the sensor exposes a frame interval at the register
level (this will only be applicable to sensors containing an ISP). What
sensor are you using ?

> +	if (ret) {
> +		LOG(V4L2, Debug)
> +			<< "Unable to get frame interval on pad " << pad
> +			<< ": " << strerror(-ret);
> +		return ret;
> +	}
> +
> +	frameInterval->numerator = subdevFrameInterval.interval.numerator;
> +	frameInterval->denominator = subdevFrameInterval.interval.denominator;
> +
> +	return 0;
> +}
> +
> +int V4L2Subdevice::setFrameInterval(unsigned int pad, Fraction *frameInterval)
> +{
> +	struct v4l2_subdev_frame_interval subdevFrameInterval = {};
> +	struct v4l2_fract fract = { frameInterval->numerator,
> +				    frameInterval->denominator };
> +
> +	subdevFrameInterval.pad = pad;
> +	subdevFrameInterval.interval = fract;
> +
> +	int ret = ioctl(VIDIOC_SUBDEV_S_FRAME_INTERVAL, &subdevFrameInterval);
> +	if (ret) {
> +		LOG(V4L2, Debug)
> +			<< "Unable to set frame interval on pad " << pad
> +			<< ": " << strerror(-ret);
> +		return ret;
> +	}
> +
> +	frameInterval->numerator = subdevFrameInterval.interval.numerator;
> +	frameInterval->denominator = subdevFrameInterval.interval.denominator;
> +
> +	return 0;
> +}
> +
>  /**
>   * \brief Create a new video subdevice instance from \a entity in media device
>   * \a media

-- 
Regards,

Laurent Pinchart