Linaro-mm-sig January 2012

linaro-mm-sig@lists.linaro.org

42 participants
23 discussions

[RFC v2 0/2] Introduce DMA buffer sharing mechanism

by Sumit Semwal

Hello Everyone, This is RFC v2 for DMA buffer sharing mechanism - changes from v1 are in the changelog below. 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 an attempt to define 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 map_dma_buf and unmap_dma_buf 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(a)arndb.de>, Rob Clark <rob(a)ti.com> and Daniel Vetter <daniel(a)ffwll.ch>. The implementation is inspired from proof-of-concept patch-set from Tomasz Stanislawski <t.stanislaws(a)samsung.com>, who demonstrated buffer sharing between two v4l2 devices. [2] References: [1]: https://wiki.linaro.org/OfficeofCTO/MemoryManagement [2]: http://lwn.net/Articles/454389 Patchset based on top of 3.2-rc3, the current version can be found at http://git.linaro.org/gitweb?p=people/sumitsemwal/linux-3.x.git Branch: dma-buf-upstr-v2 Earlier version at: https://lkml.org/lkml/2011/10/11/92 Best regards, ~Sumit Semwal History: v2: - Review comments incorporated: - from Tomasz Stanislawski [https://lkml.org/lkml/2011/10/14/136] - kzalloc moved out of critical section - corrected some in-code comments - from Dave Airlie [https://lkml.org/lkml/2011/11/25/123] - from Daniel Vetter and Rob Clark [https://lkml.org/lkml/2011/11/26/53] - use struct sg_table in place of struct scatterlist - rename {get,put}_scatterlist to {map,unmap}_dma_buf - add new wrapper APIs dma_buf_{map,unmap}_attachment for ease of users - documentation updates as per review comments from Randy Dunlap [https://lkml.org/lkml/2011/10/12/439] v1: original Sumit Semwal (2): dma-buf: Introduce dma buffer sharing mechanism dma-buf: Documentation for buffer sharing framework Documentation/dma-buf-sharing.txt | 223 ++++++++++++++++++++++++++++ drivers/base/Kconfig | 10 ++ drivers/base/Makefile | 1 + drivers/base/dma-buf.c | 290 +++++++++++++++++++++++++++++++++++++ include/linux/dma-buf.h | 176 ++++++++++++++++++++++ 5 files changed, 700 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

12 years, 11 months

[PATCH] cma: fix limit adjustment in dma_declare_contiguous()

by Mans Rullgard

The upper limit needs to be rounded down to a multiple of the alignment, not up. Signed-off-by: Mans Rullgard <mans.rullgard(a)linaro.org> --- drivers/base/dma-contiguous.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c index 924c052..e10120f 100644 --- a/drivers/base/dma-contiguous.c +++ b/drivers/base/dma-contiguous.c @@ -256,7 +256,7 @@ int __init dma_declare_contiguous(struct device *dev, unsigned long size, alignment = PAGE_SIZE << max(MAX_ORDER, pageblock_order); base = ALIGN(base, alignment); size = ALIGN(size, alignment); - limit = ALIGN(limit, alignment); + limit &= ~(alignment - 1); /* Reserve memory */ if (base) { -- 1.7.8.3

12 years, 11 months

[RFC v3 0/2] Introduce DMA buffer sharing mechanism

by Sumit Semwal

Hello Everyone, This is RFC v3 for DMA buffer sharing mechanism - changes from v2 are in the changelog below. 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 an attempt to define 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 map_dma_buf and unmap_dma_buf 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(a)arndb.de>, Rob Clark <rob(a)ti.com> and Daniel Vetter <daniel(a)ffwll.ch>. The implementation is inspired from proof-of-concept patch-set from Tomasz Stanislawski <t.stanislaws(a)samsung.com>, who demonstrated buffer sharing between two v4l2 devices. [2] References: [1]: https://wiki.linaro.org/OfficeofCTO/MemoryManagement [2]: http://lwn.net/Articles/454389 Patchset based on top of 3.2-rc3, the current version can be found at http://git.linaro.org/gitweb?p=people/sumitsemwal/linux-3.x.git Branch: dma-buf-upstr-v2 Earlier versions: v2 at: https://lkml.org/lkml/2011/12/2/53 v1 at: https://lkml.org/lkml/2011/10/11/92 Best regards, ~Sumit Semwal History: v3: - Review comments incorporated: - from Konrad Rzeszutek Wilk [https://lkml.org/lkml/2011/12/3/45] - replaced BUG_ON with WARN_ON - various places - added some error-checks - replaced EXPORT_SYMBOL with EXPORT_SYMBOL_GPL - some cosmetic / documentation comments - from Arnd Bergmann, Daniel Vetter, Rob Clark [https://lkml.org/lkml/2011/12/5/321] - removed mmap() fop and dma_buf_op, also the sg_sync* operations, and documented that mmap is not allowed for exported buffer - updated documentation to clearly state when migration is allowed - changed kconfig - some error code checks - from Rob Clark [https://lkml.org/lkml/2011/12/5/572] - update documentation to allow map_dma_buf to return -EINTR v2: - Review comments incorporated: - from Tomasz Stanislawski [https://lkml.org/lkml/2011/10/14/136] - kzalloc moved out of critical section - corrected some in-code comments - from Dave Airlie [https://lkml.org/lkml/2011/11/25/123] - from Daniel Vetter and Rob Clark [https://lkml.org/lkml/2011/11/26/53] - use struct sg_table in place of struct scatterlist - rename {get,put}_scatterlist to {map,unmap}_dma_buf - add new wrapper APIs dma_buf_{map,unmap}_attachment for ease of users - documentation updates as per review comments from Randy Dunlap [https://lkml.org/lkml/2011/10/12/439] v1: original Sumit Semwal (2): dma-buf: Introduce dma buffer sharing mechanism dma-buf: Documentation for buffer sharing framework Documentation/dma-buf-sharing.txt | 222 ++++++++++++++++++++++++++++ drivers/base/Kconfig | 10 ++ drivers/base/Makefile | 1 + drivers/base/dma-buf.c | 289 +++++++++++++++++++++++++++++++++++++ include/linux/dma-buf.h | 172 ++++++++++++++++++++++ 5 files changed, 694 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

12 years, 11 months

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Linaro-mm-sig January 2012