[libcamera-devel] [PATCH v6 3/3] libcamera: Add exportFrameBuffers in HeapAllocator

[Laurent Pinchart]

On Mon, May 29, 2023 at 10:02:18AM +0200, Jacopo Mondi via libcamera-devel wrote:
> Hi Harvey
> 
> On Mon, May 22, 2023 at 08:35:08AM +0000, Harvey Yang via libcamera-devel wrote:
> > From: Cheng-Hao Yang <chenghaoyang at chromium.org>
> 
> This is the same email address with 2 different names. Unless this is
> intentional could you change the authorship of the patch and use a
> single identity (git commit --amend --autor="...")
> 
> > Add a helper function exportFrameBuffers in HeapAllocator to make it
> > easier to use.
> >
> > Signed-off-by: Harvey Yang <chenghaoyang at chromium.org>
> > ---
> >  include/libcamera/internal/heap_allocator.h |  9 +++
> >  src/libcamera/heap_allocator.cpp            | 62 +++++++++++++++++++++
> >  2 files changed, 71 insertions(+)
> >
> > diff --git a/include/libcamera/internal/heap_allocator.h b/include/libcamera/internal/heap_allocator.h
> > index 92d4488a..92beaaa4 100644
> > --- a/include/libcamera/internal/heap_allocator.h
> > +++ b/include/libcamera/internal/heap_allocator.h
> > @@ -9,12 +9,16 @@
> >  #pragma once
> >
> >  #include <stddef.h>
> > +#include <vector>
> >
> >  #include <libcamera/base/unique_fd.h>
> >
> >  namespace libcamera {
> >
> > +class Camera;
> > +class FrameBuffer;
> >  class Heap;
> > +class Stream;
> >
> >  class HeapAllocator
> >  {
> > @@ -24,7 +28,12 @@ public:
> >  	bool isValid() const;
> >  	UniqueFD alloc(const char *name, std::size_t size);
> >
> > +	int exportFrameBuffers(Camera *camera, Stream *stream,
> > +			       std::vector<std::unique_ptr<FrameBuffer>> *buffers);
> > +
> >  private:
> > +	std::unique_ptr<FrameBuffer> createBuffer(Stream *stream);
> > +
> >  	std::unique_ptr<Heap> heap_;
> >  };
> >
> > diff --git a/src/libcamera/heap_allocator.cpp b/src/libcamera/heap_allocator.cpp
> > index 8f99f590..e99cdbe5 100644
> > --- a/src/libcamera/heap_allocator.cpp
> > +++ b/src/libcamera/heap_allocator.cpp
> > @@ -22,6 +22,12 @@
> >
> >  #include <libcamera/base/log.h>
> >
> > +#include <libcamera/camera.h>
> > +#include <libcamera/framebuffer.h>
> > +#include <libcamera/stream.h>
> > +
> > +#include "libcamera/internal/formats.h"
> > +
> >  namespace libcamera {
> >
> >  /*
> > @@ -227,4 +233,60 @@ UniqueFD HeapAllocator::alloc(const char *name, std::size_t size)
> >  	return heap_->alloc(name, size);
> >  }
> >
> > +int HeapAllocator::exportFrameBuffers([[maybe_unused]] Camera *camera, Stream *stream,
> > +				      std::vector<std::unique_ptr<FrameBuffer>> *buffers)

Why do you pass a camera pointer to this function if it's unused ?

> > +{
> > +	unsigned int count = stream->configuration().bufferCount;

You're creating a tight dependency between the allocator and the stream
here, as you require the stream to have already been configured, and
rely on the current configuration. Passing a stream configuration
explicitly would be better to make the allocator more generic.

> > +
> > +	/** \todo Support multiplanar allocations */

I'd like to see this being addressed already, as it's a key requirement
that will show whether the API design is good or not.

> > +
> > +	for (unsigned i = 0; i < count; ++i) {
> > +		std::unique_ptr<FrameBuffer> buffer = createBuffer(stream);
> > +		if (!buffer) {
> > +			LOG(HeapAllocator, Error) << "Unable to create buffer";
> > +
> > +			buffers->clear();
> > +			return -EINVAL;
> > +		}
> > +
> > +		buffers->push_back(std::move(buffer));
> > +	}
> > +
> > +	return count;
> > +}
> > +
> > +std::unique_ptr<FrameBuffer> HeapAllocator::createBuffer(Stream *stream)
> > +{
> > +	std::vector<FrameBuffer::Plane> planes;
> > +
> > +	unsigned int frameSize = stream->configuration().frameSize;
> > +	int pageSize = getpagesize();
> > +	/** Allocation size need to be a direct multiple of |pageSize|. */
> 
> No need for /**, just use /*
> 
> > +	unsigned int numPage = (frameSize + pageSize - 1) / pageSize;

What are the pros and cons for rounding it up to the page size here
compared to the alloc() function ? Does the kernel require a rounded
size, of will it round internally ?

> > +
> > +	UniqueFD fd = alloc("FrameBuffer", numPage * pageSize);
> > +	if (!fd.isValid())
> > +		return nullptr;
> > +
> > +	auto info = PixelFormatInfo::info(stream->configuration().pixelFormat);
> > +	SharedFD shared_fd(std::move(fd));
> 
> s/shared_fd/sharedFd/
> 
> > +	unsigned int offset = 0;
> > +	for (size_t i = 0; i < info.planes.size(); ++i) {
> > +		unsigned int planeSize = info.planeSize(stream->configuration().size, i);

This doesn't take line stride into account.

> > +		if (planeSize == 0)
> > +			continue;
> > +
> > +		/** \todo We don't support allocating buffers with a dedicated fd per plane */

This then makes the buffer incompatible with V4L2, that seems to be a
bad issue for a generic allocator in libcamera.

> > +		FrameBuffer::Plane plane;
> > +		plane.fd = shared_fd;
> > +		plane.offset = offset;
> > +		plane.length = planeSize;
> > +		planes.push_back(std::move(plane));
> > +
> > +		offset += planeSize;
> > +	}
> > +
> > +	return std::make_unique<FrameBuffer>(planes);
> > +}
> > +
> 
> Only minors, the patch looks good. The series looks good as well,
> please add documentation and fix all the minors and I think we can
> collect it :)

I'm afraid I disagree. See my comment in patch 2/3, in addition to the
above.

> >  } /* namespace libcamera */

-- 
Regards,

Laurent Pinchart