genode/base/include/rom_session/rom_session.h
Norman Feske 9a00ad7ae3 Support for dynamic ROM sessions, fix #170
This patch introduces support for ROM sessions that update their
provided data during the lifetime of the session. The 'Rom_session'
interface had been extended with the new 'release()' and 'sigh()'
functions, which are needed to support the new protocol. All ROM
services have been updated to the new interface.

Furthermore, the patch changes the child policy of init
with regard to the handling of configuration files. The 'Init::Child'
used to always provide the ROM dataspace with the child's config file
via a locally implemented ROM service. However, for dynamic ROM
sessions, we need to establish a session to the real supplier of the ROM
data. This is achieved by using a new 'Child_policy_redirect_rom_file'
policy to handle the 'configfile' rather than handling the 'configfile'
case entirely within 'Child_config'.

To see the new facility in action, the new 'os/run/dynamic_config.run'
script provides a simple scenario. The config file of the test program
is provided by a service, which generates and updates the config data
at regular intervals.

In addition, new support has been added to let slaves use dynamic
reconfiguration. By using the new 'Child_policy_dynamic_rom_file', the
configuration of a slave can be changed dynamically at runtime via the
new 'configure()' function.

The config is provided as plain null-terminated string (instead of a
dataspace capability) because we need to buffer the config data anyway.
So there is no benefit of using a dataspace. For buffering configuration
data, a 'Ram_session' must be supplied. If no 'Ram_session' is specified
at construction time of a 'Slave_policy', no config is supplied to the
slave (which is still a common case).

An example for dynamically reconfiguring a slave is provided by
'os/run/dynamic_config_slave.run'.
2012-04-05 11:25:26 +02:00

83 lines
2.6 KiB
C++

/*
* \brief ROM session interface
* \author Norman Feske
* \date 2006-07-06
*
* A ROM session corresponds to an open file. The file name is specified as an
* argument on session creation.
*/
/*
* 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__ROM_SESSION__ROM_SESSION_H_
#define _INCLUDE__ROM_SESSION__ROM_SESSION_H_
#include <dataspace/capability.h>
#include <session/session.h>
#include <base/signal.h>
namespace Genode {
struct Rom_dataspace : Dataspace { };
typedef Capability<Rom_dataspace> Rom_dataspace_capability;
struct Rom_session : Session
{
static const char *service_name() { return "ROM"; }
virtual ~Rom_session() { }
/**
* Request dataspace containing the ROM session data
*
* \return capability to ROM dataspace
*
* The capability may be invalid.
*
* Consecutive calls of this functions are not guaranteed to return the
* same dataspace as dynamic ROM sessions may update the ROM data
* during the lifetime of the session. When calling the function, the
* server may destroy the old dataspace and replace it with a new one
* containing the updated data. Hence, prior calling this function, the
* client should make sure to detach the previously requested dataspace
* from its local address space.
*/
virtual Rom_dataspace_capability dataspace() = 0;
/**
* Register signal handler to be notified of ROM data changes
*
* The ROM session interface allows for the implementation of ROM
* services that dynamically update the data exported as ROM dataspace
* during the lifetime of the session. This is useful in scenarios
* where this data is generated rather than originating from a static
* file, for example to update a program's configuration at runtime.
*
* By installing a signal handler using the 'sigh()' function, the
* client will receive a notification each time the data changes at the
* server. From the client's perspective, the original data contained
* in the currently used dataspace remains unchanged until the client
* calls 'dataspace()' the next time.
*/
virtual void sigh(Signal_context_capability sigh) = 0;
/*********************
** RPC declaration **
*********************/
GENODE_RPC(Rpc_dataspace, Rom_dataspace_capability, dataspace);
GENODE_RPC(Rpc_sigh, void, sigh, Signal_context_capability);
GENODE_RPC_INTERFACE(Rpc_dataspace, Rpc_sigh);
};
}
#endif /* _INCLUDE__ROM_SESSION__ROM_SESSION_H_ */