[libcamera-devel] [PATCH v4 3/3] libcamera: Add exportFrameBuffers in HeapAllocator

[Cheng-Hao Yang]

Thanks Jacopo!

On Sun, May 14, 2023 at 12:29 AM Jacopo Mondi <jacopo.mondi at ideasonboard.com>
wrote:

> Hi Harvey
>
> On Tue, Mar 28, 2023 at 05:55:34PM +0800, Harvey Yang via libcamera-devel
> wrote:
> > From: Cheng-Hao Yang <chenghaoyang at chromium.org>
> >
> > Add a helper function exportFrameBuffers in HeapAllocator to make it
> > easier to use.
>
> Will you use these with the Virtual pipeline handler ?
>
>
Yes, you can find it in |PipelindHandlerVirtual::exportFrameBuffer|.
Ref: https://patchwork.libcamera.org/patch/18533/



> >
> > Signed-off-by: Harvey Yang <chenghaoyang at chromium.org>
> > ---
> >  include/libcamera/heap_allocator.h | 11 ++++++
> >  src/libcamera/heap_allocator.cpp   | 56 ++++++++++++++++++++++++++++++
> >  2 files changed, 67 insertions(+)
> >
> > diff --git a/include/libcamera/heap_allocator.h
> b/include/libcamera/heap_allocator.h
> > index cd7ed1a3..076f0951 100644
> > --- a/include/libcamera/heap_allocator.h
> > +++ b/include/libcamera/heap_allocator.h
> > @@ -8,6 +8,7 @@
> >  #pragma once
> >
> >  #include <stddef.h>
> > +#include <vector>
> >
> >  #include <libcamera/base/unique_fd.h>
> >
> > @@ -15,6 +16,11 @@
> >
> >  namespace libcamera {
> >
> > +class Camera;
> > +class Stream;
> > +class FrameBuffer;
> > +class PixelFormatInfo;
>
> Not used
>
>
Removed.


> > +
> >  class HeapAllocator
> >  {
> >  public:
> > @@ -23,7 +29,12 @@ public:
> >       bool isValid() const { return heap_->isValid(); }
> >       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 179c2c21..33e9eaca 100644
> > --- a/src/libcamera/heap_allocator.cpp
> > +++ b/src/libcamera/heap_allocator.cpp
> > @@ -17,7 +17,11 @@
> >
> >  #include <libcamera/base/log.h>
> >
> > +#include <libcamera/camera.h>
> >  #include <libcamera/dma_heap.h>
> > +#include <libcamera/framebuffer.h>
> > +#include <libcamera/internal/formats.h>
> > +#include <libcamera/stream.h>
> >  #include <libcamera/udma_heap.h>
> >
> >  namespace libcamera {
> > @@ -43,4 +47,56 @@ 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)
> > +{
> > +     unsigned int count = stream->configuration().bufferCount;
> > +
> > +     /** \todo: Support multiplanar allocations */
>
> no : after \todo
>
>
Done

> +
> > +     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;
> > +
> > +     int num_page = (stream->configuration().frameSize + getpagesize()
> - 1) / getpagesize();
>
> Could you break this rather long line ?
>

Defined "frameSize" and "pageSize" beforehand. Should be shorter now.


> Can num_page be unsigned ?
>

Sure.


> libcamera uses camelCase and not snake_case for variables
>
>         unsigned int numPage = (stream->configuration().frameSize +
> getpagesize() - 1)
>                              / getpagesize();
>
> What are the implications of overallocating ? The last plane will be
> slightly larger, is this an issue at all ?
>
>
The allocation only works if the requested size is a direct multiple of
|getpagesize()|. Added a comment.
Ref:
https://elixir.bootlin.com/linux/latest/source/tools/testing/selftests/drivers/dma-buf/udmabuf.c#L72


> > +
> > +     UniqueFD fd = alloc("Buffer", num_page * getpagesize());
>
> What are the implications of using the same name ?
>
>
Since it's a private function that is only called by |exportFrameBuffer|,
renamed it to "FrameBuffer" instead.


> > +     if (!fd.isValid())
> > +             return nullptr;
> > +
> > +     auto info =
> PixelFormatInfo::info(stream->configuration().pixelFormat);
> > +     SharedFD shared_fd(std::move(fd));
> > +     unsigned int offset = 0;
> > +     for (long unsigned int i = 0; i < info.planes.size(); ++i) {
>
> Does this need to be long ?
>
>
I should use size_t instead.


> > +             unsigned int planeSize =
> info.planeSize(stream->configuration().size, i);
>
> configuration().size is the size in pixel, is this intended ?
>
>
Yes, I guess so, according to the comment of PixelFormatInfo:
https://github.com/kbingham/libcamera/blob/master/src/libcamera/formats.cpp#L1056


> > +             if (planeSize == 0)
> > +                     continue;
> > +
> > +             FrameBuffer::Plane plane;
>
> I would note down a \todo to remind that we don't support allocating
> buffers with a dedicated fd per plane
>
>
Is it preferred to do so? I guess we can also support that by calling
|alloc()| multiple times...?


> Sorry, lot of questions :)
>
>
Thanks for doing so :)


> Cheers
>   j
>
>
> > +             plane.fd = shared_fd;
> > +             plane.offset = offset;
> > +             plane.length = planeSize;
> > +             planes.push_back(std::move(plane));
> > +
> > +             offset += planeSize;
> > +     }
> > +
> > +     return std::make_unique<FrameBuffer>(planes);
> > +}
> > +
> >  } /* namespace libcamera */
> > --
> > 2.40.0
> >
>
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