linux-kernel - [RFC 0/2] Introduce dma buffer sharing mechanism

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Message-ID: <1318325033-32688-1-git-send-email-sumit.semwal@ti.com>
Date:	Tue, 11 Oct 2011 14:53:51 +0530
From:	Sumit Semwal <sumit.semwal@...com>
To:	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-mm@...ck.org>,
	<linaro-mm-sig@...ts.linaro.org>,
	<dri-devel@...ts.freedesktop.org>, <linux-media@...r.kernel.org>
CC:	<linux@....linux.org.uk>, <arnd@...db.de>,
	<jesse.barker@...aro.org>, <m.szyprowski@...sung.com>,
	<rob@...com>, <daniel@...ll.ch>, <t.stanislaws@...sung.com>,
	Sumit Semwal <sumit.semwal@...com>
Subject: [RFC 0/2] Introduce dma buffer sharing mechanism

Hello Everyone,

Various subsystems - V4L2, GPU-accessors, DRI to name a few - have felt the 
need to have a common mechanism to share memory buffers across different
devices - ARM, video hardware, GPU.

This need comes forth from a variety of use cases including cameras, image 
processing, video recorders, sound processing, DMA engines, GPU and display
buffers, and others.

This RFC is the first attempt in defining such a buffer sharing mechanism- it is
the result of discussions from a couple of memory-management mini-summits held
by Linaro to understand and address common needs around memory management. [1]

A new dma_buf buffer object is added, with operations and API to allow easy
sharing of this buffer object across devices.

The framework allows:
- a new buffer-object to be created with fixed size.
- different devices to 'attach' themselves to this buffer, to facilitate
  backing storage negotiation, using dma_buf_attach() API.
- association of a file pointer with each user-buffer and associated
   allocator-defined operations on that buffer. This operation is called the
   'export' operation.
- this exported buffer-object to be shared with the other entity by asking for
   its 'file-descriptor (fd)', and sharing the fd across.
- a received fd to get the buffer object back, where it can be accessed using
   the associated exporter-defined operations.
- the exporter and user to share the scatterlist using get_scatterlist and
   put_scatterlist operations.

Documentation present in the patch-set gives more details.

This is based on design suggestions from many people at the mini-summits,
most notably from Arnd Bergmann <arnd@...db.de>, Rob Clark <rob@...com> and
Daniel Vetter <daniel@...ll.ch>.

The implementation is inspired from proof-of-concept patch-set from
Tomasz Stanislawski <t.stanislaws@...sung.com>, who demonstrated buffer sharing
between two v4l2 devices. [2]

References:
[1]: https://wiki.linaro.org/OfficeofCTO/MemoryManagement
[2]: http://lwn.net/Articles/454389

Sumit Semwal (2):
  dma-buf: Introduce dma buffer sharing mechanism
  dma-buf: Documentation for buffer sharing framework

 Documentation/dma-buf-sharing.txt |  210 ++++++++++++++++++++++++++++++++
 drivers/base/Kconfig              |   10 ++
 drivers/base/Makefile             |    1 +
 drivers/base/dma-buf.c            |  242 +++++++++++++++++++++++++++++++++++++
 include/linux/dma-buf.h           |  162 +++++++++++++++++++++++++
 5 files changed, 625 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/dma-buf-sharing.txt
 create mode 100644 drivers/base/dma-buf.c
 create mode 100644 include/linux/dma-buf.h

-- 
1.7.4.1

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