On Tue, Dec 20, 2011 at 2:20 PM, Dave Airlie <airlied@xxxxxxxxx> wrote: >>> >>> 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@xxxxxxxx>, Rob Clark <rob@xxxxxx> and >>> Daniel Vetter <daniel@xxxxxxxx>. >>> >>> The implementation is inspired from proof-of-concept patch-set from >>> Tomasz Stanislawski <t.stanislaws@xxxxxxxxxxx>, 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 >> >> I think this is a really good v1 version of dma_buf. It contains all the >> required bits (with well-specified semantics in the doc patch) to >> implement some basic use-cases and start fleshing out the integration with >> various subsystem (like drm and v4l). All the things still under >> discussion like >> - userspace mmap support >> - more advanced (and more strictly specified) coherency models >> - and shared infrastructure for implementing exporters >> are imo much clearer once we have a few example drivers at hand and a >> better understanding of some of the insane corner cases we need to be able >> to handle. >> >> And I think any risk that the resulting clarifications will break a basic >> use-case is really minimal, so I think it'd be great if this could go into >> 3.3 (maybe as some kind of staging/experimental infrastructure). >> >> Hence for both patches: >> Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx> > > Yeah I'm with Daniel, I like this one, I can definitely build the drm > buffer sharing layer on top of this. > > How do we see this getting merged? I'm quite happy to push it to Linus > if we don't have an identified path, though it could go via a Linaro > tree as well. > > so feel free to add: > Reviewed-by: Dave Airlie <airlied@xxxxxxxxxx> fwiw, patches to share buffers between drm and v4l2 are here: https://github.com/robclark/kernel-omap4/commits/drmplane-dmabuf (need a bit of cleanup before the vb2 patches are submitted.. but that is unrelated to the dmabuf patches) so, Reviewed-and-Tested-by: Rob Clark <rob.clark@xxxxxxxxxx> > Dave. > -- > To unsubscribe from this list: send the line "unsubscribe linux-media" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
