[libcamera-devel] [PATCH 3/4] ipa: vimc: Map and unmap buffers

[Laurent Pinchart]

Hi Umang,

Thank you for the patch.

On Fri, Aug 06, 2021 at 03:44:08PM +0530, Umang Jain wrote:
> Since VIMC is a virtual test driver, the support for IPA
> buffers(parameter and statistics) is missing. We could create

s/buffers/buffers /

> our own and pass it around, but created buffers needs to be
> backed by dmabuf file-descriptors ideally.
> 
> This might prove cubersome given that we use vimc for test purposes.
> Hence, pass actual frame data buffers into the IPA instead, which
> would result in exercising these code paths for now. Introduce plumbing
> support for mapping and un-mapping of these buffers into the IPA.

I know what this is about, but if I didn't I'd have trouble following
the rationale. Here's a possible improvement.


VIMC is a virtual test driver that doesn't generate statistics or
consume parameters buffers. Its pipeline handler thus doesn't map any
buffer to the IPA. This limits the ability to test corresponding code
paths in unit tests, as they use VIMC extensively.

Creating fake statistics and parameters buffers would be cumbersome. Map
the frame buffers to the IPA instead, to extend test coverage.

> Signed-off-by: Umang Jain <umang.jain at ideasonboard.com>
> ---
>  include/libcamera/ipa/vimc.mojom     |  3 +++
>  src/ipa/vimc/vimc.cpp                | 26 ++++++++++++++++++++++++++
>  src/libcamera/pipeline/vimc/vimc.cpp | 25 ++++++++++++++++++++++++-
>  3 files changed, 53 insertions(+), 1 deletion(-)
> 
> diff --git a/include/libcamera/ipa/vimc.mojom b/include/libcamera/ipa/vimc.mojom
> index 99b6412b..8452461d 100644
> --- a/include/libcamera/ipa/vimc.mojom
> +++ b/include/libcamera/ipa/vimc.mojom
> @@ -26,6 +26,9 @@ interface IPAVimcInterface {
>  
>  	start() => (int32 ret);
>  	stop();
> +
> +	mapBuffers(array<libcamera.IPABuffer> buffers);
> +	unmapBuffers(array<uint32> ids);
>  };
>  
>  interface IPAVimcEventInterface {
> diff --git a/src/ipa/vimc/vimc.cpp b/src/ipa/vimc/vimc.cpp
> index 54d9086a..2b00687f 100644
> --- a/src/ipa/vimc/vimc.cpp
> +++ b/src/ipa/vimc/vimc.cpp
> @@ -19,6 +19,8 @@
>  #include <libcamera/ipa/ipa_interface.h>
>  #include <libcamera/ipa/ipa_module_info.h>
>  
> +#include "libcamera/internal/framebuffer.h"
> +
>  namespace libcamera {
>  
>  LOG_DEFINE_CATEGORY(IPAVimc)
> @@ -38,11 +40,15 @@ public:
>  		      const std::map<unsigned int, IPAStream> &streamConfig,
>  		      const std::map<unsigned int, ControlInfoMap> &entityControls) override;
>  
> +	void mapBuffers(const std::vector<IPABuffer> &buffers) override;
> +	void unmapBuffers(const std::vector<unsigned int> &ids) override;
> +
>  private:
>  	void initTrace();
>  	void trace(enum ipa::vimc::IPATraceCode operation);
>  
>  	int fd_;
> +	std::map<unsigned int, MappedFrameBuffer> buffers_;
>  };
>  
>  IPAVimc::IPAVimc()
> @@ -99,6 +105,26 @@ int IPAVimc::configure([[maybe_unused]] const IPACameraSensorInfo &sensorInfo,
>  	return 0;
>  }
>  
> +void IPAVimc::mapBuffers(const std::vector<IPABuffer> &buffers)
> +{
> +	for (const IPABuffer &buffer : buffers) {
> +		const FrameBuffer fb(buffer.planes);
> +		buffers_.emplace(buffer.id,
> +				 MappedFrameBuffer(&fb, PROT_READ));
> +	}
> +}
> +
> +void IPAVimc::unmapBuffers(const std::vector<unsigned int> &ids)
> +{
> +	for (unsigned int id : ids) {
> +		auto it = buffers_.find(id);
> +		if (it == buffers_.end())
> +			continue;
> +
> +		buffers_.erase(it);
> +	}
> +}
> +
>  void IPAVimc::initTrace()
>  {
>  	struct stat fifoStat;
> diff --git a/src/libcamera/pipeline/vimc/vimc.cpp b/src/libcamera/pipeline/vimc/vimc.cpp
> index b7dd6595..fa21128d 100644
> --- a/src/libcamera/pipeline/vimc/vimc.cpp
> +++ b/src/libcamera/pipeline/vimc/vimc.cpp
> @@ -45,7 +45,7 @@ class VimcCameraData : public CameraData
>  {
>  public:
>  	VimcCameraData(PipelineHandler *pipe, MediaDevice *media)
> -		: CameraData(pipe), media_(media)
> +		: CameraData(pipe), media_(media), buffers_(nullptr)
>  	{
>  	}
>  
> @@ -61,6 +61,9 @@ public:
>  	Stream stream_;
>  
>  	std::unique_ptr<ipa::vimc::IPAProxyVimc> ipa_;
> +
> +	std::vector<std::unique_ptr<FrameBuffer>> *buffers_;
> +	std::vector<IPABuffer> ipaBuffers_;
>  };
>  
>  class VimcCameraConfiguration : public CameraConfiguration
> @@ -319,6 +322,7 @@ int PipelineHandlerVimc::exportFrameBuffers(Camera *camera, Stream *stream,
>  {
>  	VimcCameraData *data = cameraData(camera);
>  	unsigned int count = stream->configuration().bufferCount;
> +	data->buffers_ = buffers;
>  
>  	return data->video_->exportBuffers(count, buffers);
>  }
> @@ -332,6 +336,19 @@ int PipelineHandlerVimc::start(Camera *camera, [[maybe_unused]] const ControlLis
>  	if (ret < 0)
>  		return ret;
>  
> +	/*
> +	 * We don't have actual parameters/statistics buffers in VIMC.
> +	 * Hence, map frame buffers to exercise IPA IPC code paths for now.
> +	 */
> +	ASSERT(data->buffers_ != nullptr);

We have a problem here. There's nothing that guarantees that the frame
buffers that have been queued have been exported by the pipeline
handler. I'm afraid we won't be able to use frame buffers for this :-(
It looks like we'll have to instead allocate fake stats buffers, even if
it's cumbersome. There are at least two options to create dmabufs from
userspace, dmabuf heaps or udmabuf. I'm not sure which one is best, but
let's take into account the default permissions that distributions set
on the related devices, to minimize issues.

> +	unsigned int ipaBufferId = 1;
> +	for (unsigned int i = 0; i< count; i++) {
> +		std::unique_ptr<FrameBuffer> &buffer = data->buffers_->at(i);
> +		buffer->setCookie(ipaBufferId++);
> +                data->ipaBuffers_.emplace_back(buffer->cookie(), buffer->planes());
> +	}
> +	data->ipa_->mapBuffers(data->ipaBuffers_);
> +
>  	ret = data->ipa_->start();
>  	if (ret) {
>  		data->video_->releaseBuffers();
> @@ -352,7 +369,13 @@ void PipelineHandlerVimc::stop(Camera *camera)
>  {
>  	VimcCameraData *data = cameraData(camera);
>  	data->video_->streamOff();
> +
> +	std::vector<unsigned int> ids;
> +	for (IPABuffer &ipabuf : data->ipaBuffers_)
> +		ids.push_back(ipabuf.id);
> +	data->ipa_->unmapBuffers(ids);
>  	data->ipa_->stop();
> +
>  	data->video_->releaseBuffers();
>  }
>  

-- 
Regards,

Laurent Pinchart