[libcamera-devel] [PATCH 2/2] libcamera: v4l2_device: Add methods to get/set format

[Kieran Bingham]

Hi Jacopo,

I only have variable/layout concerns here - which is certainly not a
blocker at the moment.

Also - if the outcome of the discussion below changes this patches
expectations - then we'll need to adapt other patches too - so that
would be a global patch fix at that point.

Thus I don't think that discussion blocks this patch.


On 28/01/2019 15:11, Jacopo Mondi wrote:
> Add methods to set and get the image format programmed on a V4L2Device
> for both the single and multi planar use case.
> 
> Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>

Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>


> ---
>  src/libcamera/include/v4l2_device.h |  10 +++
>  src/libcamera/v4l2_device.cpp       | 128 ++++++++++++++++++++++++++++
>  2 files changed, 138 insertions(+)
> 
> diff --git a/src/libcamera/include/v4l2_device.h b/src/libcamera/include/v4l2_device.h
> index c70959e..fe54220 100644
> --- a/src/libcamera/include/v4l2_device.h
> +++ b/src/libcamera/include/v4l2_device.h
> @@ -86,10 +86,20 @@ public:
>  	const char *deviceName() const { return caps_.card(); }
>  	const char *busName() const { return caps_.bus_info(); }
>  
> +	int format(V4L2DeviceFormat *fmt);
> +	int setFormat(V4L2DeviceFormat *fmt);
> +
>  private:
>  	std::string deviceNode_;
>  	int fd_;
>  	V4L2Capability caps_;
> +	enum v4l2_buf_type bufferType_;
> +
> +	int getFormatSingleplane(V4L2DeviceFormat *fmt);
> +	int setFormatSingleplane(V4L2DeviceFormat *fmt);
> +
> +	int getFormatMultiplane(V4L2DeviceFormat *fmt);
> +	int setFormatMultiplane(V4L2DeviceFormat *fmt);


Can I confirm <or prompt discussion> on our class layouts?

Have we defined a layout anywhere?

Here this creates:


class ClassName
{
public:
	ClassName();
	~ClassName();
	void publicFunctions();

	int publicData;
	bool publicBool;

private:
	int privateData;
	bool privateBool;

	int privateFunctions();
	int morePrivateFunctions();
}

Which is:
	PublicFunctions
	PublicData
	PrivateData
	PrivateFunctions


So the 'data' both public and private is sandwiched in the middle.
I don't mind this - but in my mind I thought we were doing:


class ClassName
{
public:
	ClassName();
	~ClassName();
	void publicFunctions();

	int publicData;
	bool publicBool;

private:
	int privateFunctions();
	int morePrivateFunctions();

	int privateData;
	bool privateBool;
}

Which is:
	PublicFunctions
	PublicData
	PrivateFunctions
	PrivateData

so that the public, and private (or protected) sections follow the same
sequence?

Any comments from the team here?

>  };
>  
>  } /* namespace libcamera */
> diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
> index d6143f2..5c415d0 100644
> --- a/src/libcamera/v4l2_device.cpp
> +++ b/src/libcamera/v4l2_device.cpp
> @@ -227,6 +227,15 @@ int V4L2Device::open()
>  		return -EINVAL;
>  	}
>  
> +	if (caps_.isCapture())
> +		bufferType_ = caps_.isMultiplanar()
> +			    ? V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE
> +			    : V4L2_BUF_TYPE_VIDEO_CAPTURE;
> +	else
> +		bufferType_ = caps_.isMultiplanar()
> +			    ? V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE
> +			    : V4L2_BUF_TYPE_VIDEO_OUTPUT;
> +
>  	return 0;
>  }
>  
> @@ -269,4 +278,123 @@ void V4L2Device::close()
>   * \return The string containing the device location
>   */
>  
> +/**
> + * \brief Retrieve the image format set on the V4L2 device
> + * \return 0 for success, a negative error code otherwise
> + */
> +int V4L2Device::format(V4L2DeviceFormat *fmt)
> +{> +	return caps_.isMultiplanar() ? getFormatMultiplane(fmt) :

I think the precedence is that the : would be below the ? here ?

But I'm doubting myself - so hopefully Laurent will chime in with his
preferences here.


If so perhaps we should set the following change in .clang-format:

-BreakBeforeTernaryOperators: false
+BreakBeforeTernaryOperators: true

which would produce the following:


+       return caps_.isMultiplanar() ? getFormatMultiplane(fmt)
+                                    : getFormatSingleplane(fmt);



It doesn't however align the ? with the = in the bufferType_ above:

              bufferType_ = caps_.isMultiplanar()
                          ? V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE
                          : V4L2_BUF_TYPE_VIDEO_OUTPUT;
                                    ? V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE
                                    : V4L2_BUF_TYPE_VIDEO_OUTPUT;

So again - I think that's a non-blocker currently.


> +				       getFormatSingleplane(fmt);
> +}
> +
> +/**
> + * \brief Configure an image format on the V4L2 device
> + * \return 0 for success, a negative error code otherwise
> + */
> +int V4L2Device::setFormat(V4L2DeviceFormat *fmt)
> +{
> +	return caps_.isMultiplanar() ? setFormatMultiplane(fmt) :
> +				       setFormatSingleplane(fmt);
> +}
> +
> +int V4L2Device::getFormatSingleplane(V4L2DeviceFormat *fmt)
> +{
> +	struct v4l2_format v4l2Fmt;
> +	struct v4l2_pix_format *pix = &v4l2Fmt.fmt.pix;
> +	int ret;
> +
> +	v4l2Fmt.type = bufferType_;
> +	ret = ioctl(fd_, VIDIOC_S_FMT, &v4l2Fmt);
> +	if (ret) {
> +		ret = -errno;
> +		LOG(Error) << "Unable to get format: " << strerror(-ret);
> +		return ret;
> +	}
> +
> +	fmt->width = pix->width;
> +	fmt->height = pix->height;
> +	fmt->fourcc = pix->pixelformat;
> +	fmt->planes = 1;
> +	fmt->planesFmt[0].bpl = pix->bytesperline;
> +	fmt->planesFmt[0].size = pix->sizeimage;
> +

I think we might need to cache the V4L2DeviceFormat in the V4L2Device
somewhere...

But perhaps that's not required by this patch - if something needs to
access this (like the BufferPool creation) it can handle caching the
format object.



> +	return 0;
> +}
> +
> +int V4L2Device::setFormatSingleplane(V4L2DeviceFormat *fmt)
> +{
> +	struct v4l2_format v4l2Fmt;
> +	struct v4l2_pix_format *pix = &v4l2Fmt.fmt.pix;
> +	int ret;
> +
> +	v4l2Fmt.type = bufferType_;
> +	pix->width = fmt->width;
> +	pix->height = fmt->height;
> +	pix->pixelformat = fmt->fourcc;
> +
> +	ret = ioctl(fd_, VIDIOC_S_FMT, &v4l2Fmt);
> +	if (ret) {
> +		ret = -errno;
> +		LOG(Error) << "Unable to set format: " << strerror(-ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +int V4L2Device::getFormatMultiplane(V4L2DeviceFormat *fmt)
> +{
> +	struct v4l2_format v4l2Fmt;
> +	struct v4l2_pix_format_mplane *pix = &v4l2Fmt.fmt.pix_mp;
> +	int ret;
> +
> +	v4l2Fmt.type = bufferType_;
> +	ret = ioctl(fd_, VIDIOC_G_FMT, &v4l2Fmt);
> +	if (ret) {
> +		ret = -errno;
> +		LOG(Error) << "Unable to get format: " << strerror(-ret);
> +		return ret;
> +	}
> +
> +	fmt->width = pix->width;
> +	fmt->height = pix->height;
> +	fmt->fourcc = pix->pixelformat;
> +	fmt->planes = pix->num_planes;
> +
> +	for (unsigned int i = 0; i < fmt->planes; ++i) {
> +		fmt->planesFmt[i].bpl = pix->plane_fmt[i].bytesperline;
> +		fmt->planesFmt[i].size = pix->plane_fmt[i].sizeimage;
> +	}
> +
> +	return 0;
> +}
> +
> +int V4L2Device::setFormatMultiplane(V4L2DeviceFormat *fmt)
> +{
> +	struct v4l2_format v4l2Fmt;
> +	struct v4l2_pix_format_mplane *pix = &v4l2Fmt.fmt.pix_mp;
> +	int ret;
> +
> +	v4l2Fmt.type = bufferType_;
> +	pix->width = fmt->width;
> +	pix->height = fmt->height;
> +	pix->pixelformat = fmt->fourcc;
> +	pix->num_planes = fmt->planes;
> +
> +	for (unsigned int i = 0; i < pix->num_planes; ++i) {
> +		pix->plane_fmt[i].bytesperline = fmt->planesFmt[i].bpl;
> +		pix->plane_fmt[i].sizeimage = fmt->planesFmt[i].size;
> +	}
> +
> +	ret = ioctl(fd_, VIDIOC_S_FMT, &v4l2Fmt);
> +	if (ret) {
> +		ret = -errno;
> +		LOG(Error) << "Unable to set format: " << strerror(-ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
>  } /* namespace libcamera */
> 

-- 
Regards
--
Kieran