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This patch extends the RAM session interface with the ability to allocate DMA buffers. The client specifies the type of RAM dataspace to allocate via the new 'cached' argument of the 'Ram_session::alloc()' function. By default, 'cached' is true, which correponds to the common case and the original behavior. When setting 'cached' to 'false', core takes the precautions needed to register the memory as uncached in the page table of each process that has the dataspace attached. Currently, the support for allocating DMA buffers is implemented for Fiasco.OC only. On x86 platforms, it is generally not needed. But on platforms with more relaxed cache coherence (such as ARM), user-level device drivers should always use uncacheable memory for DMA transactions.
This is generic part of the Genode implementation. It consists of two parts: :_Core_: is the ultimate root of the Genode application tree and provides abstractions for the lowest-level hardware resources such as RAM, ROM, CPU, and generic device access. All generic parts of Core can be found here - for system-specific implementations refer to the appropriate 'base-<system>' directory. :_Base libraries and protocols_: that are used by each Genode component to interact with other components. This is the glue that holds everything together.