genode/base/include/ram_session/ram_session.h

/*
 * \brief  RAM session interface
 * \author Norman Feske
 * \date   2006-05-11
 */

/*
 * Copyright (C) 2006-2012 Genode Labs GmbH
 *
 * This file is part of the Genode OS framework, which is distributed
 * under the terms of the GNU General Public License version 2.
 */

#ifndef _INCLUDE__RAM_SESSION__RAM_SESSION_H_
#define _INCLUDE__RAM_SESSION__RAM_SESSION_H_

#include <base/stdint.h>
#include <base/capability.h>
#include <base/exception.h>
#include <dataspace/capability.h>
#include <ram_session/capability.h>
#include <session/session.h>

namespace Genode {

	struct Ram_dataspace : Dataspace { };

	typedef Capability<Ram_dataspace> Ram_dataspace_capability;

	struct Ram_session : Session
	{
		static const char *service_name() { return "RAM"; }


		/*********************
		 ** Exception types **
		 *********************/

		class Alloc_failed    : public Exception    { };
		class Quota_exceeded  : public Alloc_failed { };
		class Out_of_metadata : public Alloc_failed { };

		/**
		 * Destructor
		 */
		virtual ~Ram_session() { }

		/**
		 * Allocate RAM dataspace
		 *
		 * \param  size    size of RAM dataspace
		 * \param  cached  true for cached memory, false for allocating
		 *                 uncached memory, i.e., for DMA buffers
		 *
		 * \throw  Quota_exceeded
		 * \throw  Out_of_metadata
		 * \return capability to new RAM dataspace
		 */
		virtual Ram_dataspace_capability alloc(size_t size,
		                                       bool cached = true) = 0;

		/**
		 * Free RAM dataspace
		 *
		 * \param ds  dataspace capability as returned by alloc
		 */
		virtual void free(Ram_dataspace_capability ds) = 0;

		/**
		 * Define reference account for the RAM session
		 *
		 * \param   ram_session    reference account
		 *
		 * \return  0 on success
		 *
		 * Each RAM session requires another RAM session as reference
		 * account to transfer quota to and from. The reference account can
		 * be defined only once.
		 */
		virtual int ref_account(Ram_session_capability ram_session) = 0;

		/**
		 * Transfer quota to another RAM session
		 *
		 * \param ram_session  receiver of quota donation
		 * \param amount       amount of quota to donate
		 * \return             0 on success
		 *
		 * Quota can only be transfered if the specified RAM session is
		 * either the reference account for this session or vice versa.
		 */
		virtual int transfer_quota(Ram_session_capability ram_session, size_t amount) = 0;

		/**
		 * Return current quota limit
		 */
		virtual size_t quota() = 0;

		/**
		 * Return used quota
		 */
		virtual size_t used() = 0;

		/**
		 * Return amount of available quota
		 */
		size_t avail()
		{
			size_t q = quota(), u = used();
			return q > u ? q - u : 0;
		}

		/*********************
		 ** RPC declaration **
		 *********************/

		GENODE_RPC_THROW(Rpc_alloc, Ram_dataspace_capability, alloc,
		                 GENODE_TYPE_LIST(Quota_exceeded, Out_of_metadata),
		                 size_t, bool);
		GENODE_RPC(Rpc_free, void, free, Ram_dataspace_capability);
		GENODE_RPC(Rpc_ref_account, int, ref_account, Ram_session_capability);
		GENODE_RPC(Rpc_transfer_quota, int, transfer_quota, Ram_session_capability, size_t);
		GENODE_RPC(Rpc_quota, size_t, quota);
		GENODE_RPC(Rpc_used, size_t, used);

		GENODE_RPC_INTERFACE(Rpc_alloc, Rpc_free, Rpc_ref_account,
		                     Rpc_transfer_quota, Rpc_quota, Rpc_used);
	};
}

#endif /* _INCLUDE__RAM_SESSION__RAM_SESSION_H_ */