On Tue, Oct 11, 2011 at 10:23 AM, Sumit Semwal <sumit.semwal@xxxxxx> wrote: > This is the first step in defining a dma buffer sharing mechanism. > > A new buffer object dma_buf 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. > > Atleast one 'attach()' call is required to be made prior to calling the > get_scatterlist() operation. > > Couple of building blocks in get_scatterlist() are added to ease introduction > of sync'ing across exporter and users, and late allocation by the exporter. > > mmap() file operation is provided for the associated 'fd', as wrapper over the > optional allocator defined mmap(), to be used by devices that might need one. > > More details are there in the documentation patch. > Some questions, I've started playing around with using this framework to do buffer sharing between DRM devices, Why struct scatterlist and not struct sg_table? it seems like I really want to use an sg_table, I'm not convinced fd's are really useful over just some idr allocated handle, so far I'm just returning the "fd" to userspace as a handle, and passing it back in the other side, so I'm not really sure what an fd wins us here, apart from the mmap thing which I think shouldn't be here anyways. (if fd's do win us more we should probably record that in the docs patch). Dave. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
