[Linaro-mm-sig] [RFC 1/2] dma-buf: Introduce dma buffer sharing mechanism

[Dave Airlie]

> But then we'd need a different set of accessors for every different
> drm/v4l/etc driver, wouldn't we?

Not any more different than you need for this, you just have a new
interface that you request a sw object from,
then mmap that object, and underneath it knows who owns it in the kernel.

mmap just feels wrong in this API, which is a buffer sharing API not a
buffer mapping API.

> I guess if sharing a buffer between multiple drm devices, there is
> nothing stopping you from having some NOT_DMABUF_MMAPABLE flag you
> pass when the buffer is allocated, then you don't have to support
> dmabuf->mmap(), and instead mmap via device and use some sort of
> DRM_CPU_PREP/FINI ioctls for synchronization..

Or we could make a generic CPU accessor that we don't have to worry about.

Dave.