[libcamera-devel] [PATCH 1/9] libcamera: bayer_format: Add toMbusCode method

[Jacopo Mondi]

Hi David
   sorry to revive this, but I'm carrying this series in my tree and I
just found a bug in this patches


On Thu, Nov 24, 2022 at 01:12:12PM +0100, Jacopo Mondi wrote:
> From: David Plowman <david.plowman at raspberrypi.com>
>
> This makes it easier to perform transformations on Bayer type mbus
> codes by converting them to a BayerFormat, doing the transform, and
> then converting them back again.
>
> Signed-off-by: David Plowman <david.plowman at raspberrypi.com>
> Reviewed-by: Jacopo Mondi <jacopo at jmondi.org>
> ---
>  include/libcamera/internal/bayer_format.h |  1 +
>  src/libcamera/bayer_format.cpp            | 11 +++++++++++
>  2 files changed, 12 insertions(+)
>
> diff --git a/include/libcamera/internal/bayer_format.h b/include/libcamera/internal/bayer_format.h
> index 78ba3969913d..3601dccb7228 100644
> --- a/include/libcamera/internal/bayer_format.h
> +++ b/include/libcamera/internal/bayer_format.h
> @@ -47,6 +47,7 @@ public:
>  	}
>
>  	static const BayerFormat &fromMbusCode(unsigned int mbusCode);
> +	unsigned int toMbusCode() const;
>  	bool isValid() const { return bitDepth != 0; }
>
>  	std::string toString() const;
> diff --git a/src/libcamera/bayer_format.cpp b/src/libcamera/bayer_format.cpp
> index f27cc1662d25..fdbc4af1dcc0 100644
> --- a/src/libcamera/bayer_format.cpp
> +++ b/src/libcamera/bayer_format.cpp
> @@ -226,6 +226,17 @@ const BayerFormat &BayerFormat::fromMbusCode(unsigned int mbusCode)
>  		return it->second;
>  }
>
> +/**
> + * \brief Retrieve the media bus code corresponding this this BayerFormat
> + * \return The corresponding media bus code, or zero if none was found
> + */
> +unsigned int BayerFormat::toMbusCode() const
> +{
> +	auto it = std::find_if(mbusCodeToBayer.begin(), mbusCodeToBayer.end(),
> +			       [this](const auto &i) { return i.second == *this; });
> +	return it != mbusCodeToBayer.end() ? it->first : 0;

I'm working with a sensor that produces MEDIA_BUS_FMT_SBGGR10_1X10
It doesn't register flips, so the bayer pattern should not be changed

The code you added in the next patch for the CameraSensor class goes
as

	for (const auto &format : formats) {
		unsigned int mbusCode = format.first;
		BayerFormat bayerFormat = BayerFormat::fromMbusCode(mbusCode);

		if (bayerFormat.isValid())
			mbusCode = bayerFormat.transform(transform).toMbusCode();

		if (mbusCode)
			formats_[mbusCode] = std::move(format.second);
	}


The first

		BayerFormat bayerFormat = BayerFormat::fromMbusCode(mbusCode);

returns  { BayerFormat::BGGR, 10, BayerFormat::Packing::None }

we go throgh a transform() which does nothing as it receives Indentity
and then call toMbusCode() on it

The above implementation of toMbusCode() walks the mbusCodeToBayer map
looking for a matching bayer. Look at this table section

	{ MEDIA_BUS_FMT_SBGGR10_2X8_PADHI_BE, { BayerFormat::BGGR, 10, BayerFormat::Packing::None } },
	{ MEDIA_BUS_FMT_SBGGR10_2X8_PADHI_LE, { BayerFormat::BGGR, 10, BayerFormat::Packing::None } },
	{ MEDIA_BUS_FMT_SBGGR10_2X8_PADLO_BE, { BayerFormat::BGGR, 10, BayerFormat::Packing::None } },
	{ MEDIA_BUS_FMT_SBGGR10_2X8_PADLO_LE, { BayerFormat::BGGR, 10, BayerFormat::Packing::None } },
	{ MEDIA_BUS_FMT_SBGGR10_1X10, { BayerFormat::BGGR, 10, BayerFormat::Packing::None } },

So here we have that all the MEDIA_BUS_FMT_SBGGR10_2X8_PAD.. and
MEDIA_BUS_FMT_SBGGR10_1X10 codes match on the same
{ BayerFormat::BGGR, 10, BayerFormat::Packing::None } and I suddenly
get my original 0x3007 code transformed to 0x3003!

I'm afraid the fact mbus_code-to-BayerFormat relationship is not
unique is a blocker for this patch





> +}
> +
>  /**
>   * \fn BayerFormat::isValid()
>   * \brief Return whether a BayerFormat is valid
> --
> 2.38.1
>