288fd4e56e
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.
132 lines
3.4 KiB
C++
132 lines
3.4 KiB
C++
/*
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* \brief RAM session interface
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* \author Norman Feske
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* \date 2006-05-11
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*/
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/*
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* Copyright (C) 2006-2012 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU General Public License version 2.
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*/
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#ifndef _INCLUDE__RAM_SESSION__RAM_SESSION_H_
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#define _INCLUDE__RAM_SESSION__RAM_SESSION_H_
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#include <base/stdint.h>
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#include <base/capability.h>
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#include <base/exception.h>
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#include <dataspace/capability.h>
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#include <ram_session/capability.h>
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#include <session/session.h>
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namespace Genode {
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struct Ram_dataspace : Dataspace { };
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typedef Capability<Ram_dataspace> Ram_dataspace_capability;
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struct Ram_session : Session
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{
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static const char *service_name() { return "RAM"; }
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/*********************
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** Exception types **
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*********************/
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class Alloc_failed : public Exception { };
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class Quota_exceeded : public Alloc_failed { };
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class Out_of_metadata : public Alloc_failed { };
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/**
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* Destructor
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*/
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virtual ~Ram_session() { }
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/**
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* Allocate RAM dataspace
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*
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* \param size size of RAM dataspace
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* \param cached true for cached memory, false for allocating
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* uncached memory, i.e., for DMA buffers
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*
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* \throw Quota_exceeded
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* \throw Out_of_metadata
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* \return capability to new RAM dataspace
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*/
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virtual Ram_dataspace_capability alloc(size_t size,
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bool cached = true) = 0;
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/**
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* Free RAM dataspace
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*
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* \param ds dataspace capability as returned by alloc
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*/
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virtual void free(Ram_dataspace_capability ds) = 0;
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/**
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* Define reference account for the RAM session
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*
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* \param ram_session reference account
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*
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* \return 0 on success
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*
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* Each RAM session requires another RAM session as reference
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* account to transfer quota to and from. The reference account can
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* be defined only once.
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*/
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virtual int ref_account(Ram_session_capability ram_session) = 0;
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/**
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* Transfer quota to another RAM session
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*
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* \param ram_session receiver of quota donation
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* \param amount amount of quota to donate
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* \return 0 on success
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*
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* Quota can only be transfered if the specified RAM session is
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* either the reference account for this session or vice versa.
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*/
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virtual int transfer_quota(Ram_session_capability ram_session, size_t amount) = 0;
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/**
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* Return current quota limit
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*/
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virtual size_t quota() = 0;
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/**
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* Return used quota
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*/
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virtual size_t used() = 0;
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/**
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* Return amount of available quota
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*/
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size_t avail()
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{
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size_t q = quota(), u = used();
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return q > u ? q - u : 0;
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}
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/*********************
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** RPC declaration **
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*********************/
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GENODE_RPC_THROW(Rpc_alloc, Ram_dataspace_capability, alloc,
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GENODE_TYPE_LIST(Quota_exceeded, Out_of_metadata),
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size_t, bool);
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GENODE_RPC(Rpc_free, void, free, Ram_dataspace_capability);
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GENODE_RPC(Rpc_ref_account, int, ref_account, Ram_session_capability);
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GENODE_RPC(Rpc_transfer_quota, int, transfer_quota, Ram_session_capability, size_t);
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GENODE_RPC(Rpc_quota, size_t, quota);
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GENODE_RPC(Rpc_used, size_t, used);
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GENODE_RPC_INTERFACE(Rpc_alloc, Rpc_free, Rpc_ref_account,
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Rpc_transfer_quota, Rpc_quota, Rpc_used);
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};
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}
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#endif /* _INCLUDE__RAM_SESSION__RAM_SESSION_H_ */
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