source: mainline/uspace/lib/libc/generic/ipc.c@ badbd888

/*
 * Copyright (c) 2006 Ondrej Palkovsky
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup libc
 * @{
 * @}
 */

/** @addtogroup libcipc IPC
 * @brief HelenOS uspace IPC
 * @{
 * @ingroup libc
 */
/** @file
 */ 

#include <ipc/ipc.h>
#include <libc.h>
#include <malloc.h>
#include <errno.h>
#include <libadt/list.h>
#include <stdio.h>
#include <unistd.h>
#include <futex.h>
#include <kernel/synch/synch.h>
#include <async.h>
#include <fibril.h>
#include <assert.h>

/**
 * Structures of this type are used for keeping track of sent asynchronous calls
 * and queing unsent calls.
 */
typedef struct {
        link_t list;

        ipc_async_callback_t callback;
        void *private;
        union {
                ipc_callid_t callid;
                struct {
                        ipc_call_t data;
                        int phoneid;
                } msg;
        } u;
        fid_t fid;      /**< Fibril waiting for sending this call. */
} async_call_t;

LIST_INITIALIZE(dispatched_calls);

/** List of asynchronous calls that were not accepted by kernel.
 *
 * It is protected by async_futex, because if the call cannot be sent into the
 * kernel, the async framework is used automatically.
 */
LIST_INITIALIZE(queued_calls);

static atomic_t ipc_futex = FUTEX_INITIALIZER;

/** Make a fast synchronous call.
 *
 * Only three payload arguments can be passed using this function. However, this
 * function is faster than the generic ipc_call_sync_slow() because the payload
 * is passed directly in registers.
 *
 * @param phoneid       Phone handle for the call.
 * @param method        Requested method.
 * @param arg1          Service-defined payload argument.
 * @param arg2          Service-defined payload argument.
 * @param arg3          Service-defined payload argument.
 * @param result1       If non-NULL, the return ARG1 will be stored there.
 * @param result2       If non-NULL, the return ARG2 will be stored there.
 * @param result3       If non-NULL, the return ARG3 will be stored there.
 * @param result4       If non-NULL, the return ARG4 will be stored there.
 * @param result5       If non-NULL, the return ARG5 will be stored there.
 *
 * @return              Negative values represent errors returned by IPC.
 *                      Otherwise the RETVAL of the answer is returned.
 */
int
ipc_call_sync_fast(int phoneid, ipcarg_t method, ipcarg_t arg1, ipcarg_t arg2,
    ipcarg_t arg3, ipcarg_t *result1, ipcarg_t *result2, ipcarg_t *result3,
    ipcarg_t *result4, ipcarg_t *result5)
{
        ipc_call_t resdata;
        int callres;
        
        callres = __SYSCALL6(SYS_IPC_CALL_SYNC_FAST, phoneid, method, arg1,
            arg2, arg3, (sysarg_t) &resdata);
        if (callres)
                return callres;
        if (result1)
                *result1 = IPC_GET_ARG1(resdata);
        if (result2)
                *result2 = IPC_GET_ARG2(resdata);
        if (result3)
                *result3 = IPC_GET_ARG3(resdata);
        if (result4)
                *result4 = IPC_GET_ARG4(resdata);
        if (result5)
                *result5 = IPC_GET_ARG5(resdata);

        return IPC_GET_RETVAL(resdata);
}

/** Make a synchronous call transmitting 5 arguments of payload.
 *
 * @param phoneid       Phone handle for the call.
 * @param method        Requested method.
 * @param arg1          Service-defined payload argument.
 * @param arg2          Service-defined payload argument.
 * @param arg3          Service-defined payload argument.
 * @param arg4          Service-defined payload argument.
 * @param arg5          Service-defined payload argument.
 * @param result1       If non-NULL, storage for the first return argument.
 * @param result2       If non-NULL, storage for the second return argument.
 * @param result3       If non-NULL, storage for the third return argument.
 * @param result4       If non-NULL, storage for the fourth return argument.
 * @param result5       If non-NULL, storage for the fifth return argument.
 *
 * @return              Negative value means IPC error.
 *                      Otherwise the RETVAL of the answer.
 */
int
ipc_call_sync_slow(int phoneid, ipcarg_t method, ipcarg_t arg1, ipcarg_t arg2,
    ipcarg_t arg3, ipcarg_t arg4, ipcarg_t arg5, ipcarg_t *result1,
    ipcarg_t *result2, ipcarg_t *result3, ipcarg_t *result4, ipcarg_t *result5)
{
        ipc_call_t data;
        int callres;

        IPC_SET_METHOD(data, method);
        IPC_SET_ARG1(data, arg1);
        IPC_SET_ARG2(data, arg2);
        IPC_SET_ARG3(data, arg3);
        IPC_SET_ARG4(data, arg4);
        IPC_SET_ARG5(data, arg5);

        callres = __SYSCALL3(SYS_IPC_CALL_SYNC_SLOW, phoneid, (sysarg_t) &data,
            (sysarg_t) &data);
        if (callres)
                return callres;

        if (result1)
                *result1 = IPC_GET_ARG1(data);
        if (result2)
                *result2 = IPC_GET_ARG2(data);
        if (result3)
                *result3 = IPC_GET_ARG3(data);
        if (result4)
                *result4 = IPC_GET_ARG4(data);
        if (result5)
                *result5 = IPC_GET_ARG5(data);

        return IPC_GET_RETVAL(data);
}

/** Syscall to send asynchronous message.
 *
 * @param phoneid       Phone handle for the call.
 * @param data          Call data with the request.
 *
 * @return              Hash of the call or an error code.
 */
static ipc_callid_t _ipc_call_async(int phoneid, ipc_call_t *data)
{
        return __SYSCALL2(SYS_IPC_CALL_ASYNC_SLOW, phoneid, (sysarg_t) data);
}

/** Prolog to ipc_call_async_*() functions.
 *
 * @param private       Argument for the answer/error callback.
 * @param callback      Answer/error callback.
 *
 * @return              New, partially initialized async_call structure or NULL.
 */
static inline async_call_t *ipc_prepare_async(void *private,
    ipc_async_callback_t callback)
{
        async_call_t *call;

        call = malloc(sizeof(*call));
        if (!call) {
                if (callback)
                        callback(private, ENOMEM, NULL);
                return NULL;
        }
        call->callback = callback;
        call->private = private;

        return call;
}

/** Epilogue of ipc_call_async_*() functions.
 *
 * @param callid        Value returned by the SYS_IPC_CALL_ASYNC_* syscall.
 * @param phoneid       Phone handle through which the call was made.
 * @param call          async_call structure returned by ipc_prepare_async().
 * @param can_preempt   If non-zero, the current fibril can be preempted in this
 *                      call.
 */
static inline void ipc_finish_async(ipc_callid_t callid, int phoneid,
    async_call_t *call, int can_preempt)
{
        if (!call) { /* Nothing to do regardless if failed or not */
                futex_up(&ipc_futex);
                return;
        }

        if (callid == IPC_CALLRET_FATAL) {
                futex_up(&ipc_futex);
                /* Call asynchronous handler with error code */
                if (call->callback)
                        call->callback(call->private, ENOENT, NULL);
                free(call);
                return;
        }

        if (callid == IPC_CALLRET_TEMPORARY) {
                futex_up(&ipc_futex);

                call->u.msg.phoneid = phoneid;
                
                futex_down(&async_futex);
                list_append(&call->list, &queued_calls);

                if (can_preempt) {
                        call->fid = fibril_get_id();
                        fibril_switch(FIBRIL_TO_MANAGER);
                        /* Async futex unlocked by previous call */
                } else {
                        call->fid = 0;
                        futex_up(&async_futex);
                }
                return;
        }
        call->u.callid = callid;
        /* Add call to the list of dispatched calls */
        list_append(&call->list, &dispatched_calls);
        futex_up(&ipc_futex);
        
}

/** Make a fast asynchronous call.
 *
 * This function can only handle four arguments of payload. It is, however,
 * faster than the more generic ipc_call_async_slow().
 *
 * Note that this function is a void function.
 * During normal opertation, answering this call will trigger the callback.
 * In case of fatal error, call the callback handler with the proper error code.
 * If the call cannot be temporarily made, queue it.
 *
 * @param phoneid       Phone handle for the call.
 * @param method        Requested method.
 * @param arg1          Service-defined payload argument.
 * @param arg2          Service-defined payload argument.
 * @param arg3          Service-defined payload argument.
 * @param arg4          Service-defined payload argument.
 * @param private       Argument to be passed to the answer/error callback.
 * @param callback      Answer or error callback.
 * @param can_preempt   If non-zero, the current fibril will be preempted in
 *                      case the kernel temporarily refuses to accept more
 *                      asynchronous calls.
 */
void ipc_call_async_fast(int phoneid, ipcarg_t method, ipcarg_t arg1,
    ipcarg_t arg2, ipcarg_t arg3, ipcarg_t arg4, void *private,
    ipc_async_callback_t callback, int can_preempt)
{
        async_call_t *call = NULL;
        ipc_callid_t callid;

        if (callback) {
                call = ipc_prepare_async(private, callback);
                if (!call)
                        return;
        }

        /*
         * We need to make sure that we get callid before another thread
         * accesses the queue again.
         */
        futex_down(&ipc_futex);
        callid = __SYSCALL6(SYS_IPC_CALL_ASYNC_FAST, phoneid, method, arg1,
            arg2, arg3, arg4);

        if (callid == IPC_CALLRET_TEMPORARY) {
                if (!call) {
                        call = ipc_prepare_async(private, callback);
                        if (!call)
                                return;
                }
                IPC_SET_METHOD(call->u.msg.data, method);
                IPC_SET_ARG1(call->u.msg.data, arg1);
                IPC_SET_ARG2(call->u.msg.data, arg2);
                IPC_SET_ARG3(call->u.msg.data, arg3);
                IPC_SET_ARG4(call->u.msg.data, arg4);
                /*
                 * To achieve deterministic behavior, we always zero out the
                 * arguments that are beyond the limits of the fast version.
                 */
                IPC_SET_ARG5(call->u.msg.data, 0);
        }
        ipc_finish_async(callid, phoneid, call, can_preempt);
}

/** Make an asynchronous call transmitting the entire payload.
 *
 * Note that this function is a void function.
 * During normal opertation, answering this call will trigger the callback.
 * In case of fatal error, call the callback handler with the proper error code.
 * If the call cannot be temporarily made, queue it.
 *
 * @param phoneid       Phone handle for the call.
 * @param method        Requested method.
 * @param arg1          Service-defined payload argument.
 * @param arg2          Service-defined payload argument.
 * @param arg3          Service-defined payload argument.
 * @param arg4          Service-defined payload argument.
 * @param arg5          Service-defined payload argument.
 * @param private       Argument to be passed to the answer/error callback.
 * @param callback      Answer or error callback.
 * @param can_preempt   If non-zero, the current fibril will be preempted in
 *                      case the kernel temporarily refuses to accept more
 *                      asynchronous calls.
 *
 */
void ipc_call_async_slow(int phoneid, ipcarg_t method, ipcarg_t arg1,
    ipcarg_t arg2, ipcarg_t arg3, ipcarg_t arg4, ipcarg_t arg5, void *private,
    ipc_async_callback_t callback, int can_preempt)
{
        async_call_t *call;
        ipc_callid_t callid;

        call = ipc_prepare_async(private, callback);
        if (!call)
                return;

        IPC_SET_METHOD(call->u.msg.data, method);
        IPC_SET_ARG1(call->u.msg.data, arg1);
        IPC_SET_ARG2(call->u.msg.data, arg2);
        IPC_SET_ARG3(call->u.msg.data, arg3);
        IPC_SET_ARG4(call->u.msg.data, arg4);
        IPC_SET_ARG5(call->u.msg.data, arg5);
        /*
         * We need to make sure that we get callid before another thread
         * accesses the queue again.
         */
        futex_down(&ipc_futex);
        callid = _ipc_call_async(phoneid, &call->u.msg.data);

        ipc_finish_async(callid, phoneid, call, can_preempt);
}


/** Answer a received call - fast version.
 *
 * The fast answer makes use of passing retval and first four arguments in
 * registers. If you need to return more, use the ipc_answer_slow() instead.
 *
 * @param callid        Hash of the call being answered.
 * @param retval        Return value.
 * @param arg1          First return argument.
 * @param arg2          Second return argument.
 * @param arg3          Third return argument.
 * @param arg4          Fourth return argument.
 *
 * @return              Zero on success or a value from @ref errno.h on failure.
 */
ipcarg_t ipc_answer_fast(ipc_callid_t callid, ipcarg_t retval, ipcarg_t arg1,
    ipcarg_t arg2, ipcarg_t arg3, ipcarg_t arg4)
{
        return __SYSCALL6(SYS_IPC_ANSWER_FAST, callid, retval, arg1, arg2, arg3,
            arg4);
}

/** Answer a received call - slow full version.
 *
 * @param callid        Hash of the call being answered.
 * @param retval        Return value.
 * @param arg1          First return argument.
 * @param arg2          Second return argument.
 * @param arg3          Third return argument.
 * @param arg4          Fourth return argument.
 * @param arg5          Fifth return argument.
 *
 * @return              Zero on success or a value from @ref errno.h on failure.
 */
ipcarg_t ipc_answer_slow(ipc_callid_t callid, ipcarg_t retval, ipcarg_t arg1,
    ipcarg_t arg2, ipcarg_t arg3, ipcarg_t arg4, ipcarg_t arg5)
{
        ipc_call_t data;

        IPC_SET_RETVAL(data, retval);
        IPC_SET_ARG1(data, arg1);
        IPC_SET_ARG2(data, arg2);
        IPC_SET_ARG3(data, arg3);
        IPC_SET_ARG4(data, arg4);
        IPC_SET_ARG5(data, arg5);

        return __SYSCALL2(SYS_IPC_ANSWER_SLOW, callid, (sysarg_t) &data);
}


/** Try to dispatch queued calls from the async queue. */
static void try_dispatch_queued_calls(void)
{
        async_call_t *call;
        ipc_callid_t callid;

        /** @todo
         * Integrate intelligently ipc_futex, so that it is locked during
         * ipc_call_async_*(), until it is added to dispatched_calls.
         */
        futex_down(&async_futex);
        while (!list_empty(&queued_calls)) {
                call = list_get_instance(queued_calls.next, async_call_t, list);
                callid = _ipc_call_async(call->u.msg.phoneid,
                    &call->u.msg.data);
                if (callid == IPC_CALLRET_TEMPORARY) {
                        break;
                }
                list_remove(&call->list);

                futex_up(&async_futex);
                if (call->fid)
                        fibril_add_ready(call->fid);
                
                if (callid == IPC_CALLRET_FATAL) {
                        if (call->callback)
                                call->callback(call->private, ENOENT, NULL);
                        free(call);
                } else {
                        call->u.callid = callid;
                        futex_down(&ipc_futex);
                        list_append(&call->list, &dispatched_calls);
                        futex_up(&ipc_futex);
                }
                futex_down(&async_futex);
        }
        futex_up(&async_futex);
}

/** Handle a received answer.
 *
 * Find the hash of the answer and call the answer callback.
 *
 * @todo Make it use hash table.
 *
 * @param callid        Hash of the received answer.
 *                      The answer has the same hash as the request OR'ed with
 *                      the IPC_CALLID_ANSWERED bit.
 * @param data          Call data of the answer.
 */
static void handle_answer(ipc_callid_t callid, ipc_call_t *data)
{
        link_t *item;
        async_call_t *call;

        callid &= ~IPC_CALLID_ANSWERED;
        
        futex_down(&ipc_futex);
        for (item = dispatched_calls.next; item != &dispatched_calls;
            item = item->next) {
                call = list_get_instance(item, async_call_t, list);
                if (call->u.callid == callid) {
                        list_remove(&call->list);
                        futex_up(&ipc_futex);
                        if (call->callback)
                                call->callback(call->private, 
                                    IPC_GET_RETVAL(*data), data);
                        free(call);
                        return;
                }
        }
        futex_up(&ipc_futex);
}


/** Wait for a first call to come.
 *
 * @param call          Storage where the incoming call data will be stored.
 * @param usec          Timeout in microseconds
 * @param flags         Flags passed to SYS_IPC_WAIT (blocking, nonblocking).
 *
 * @return              Hash of the call. Note that certain bits have special
 *                      meaning. IPC_CALLID_ANSWERED will be set in an answer
 *                      and IPC_CALLID_NOTIFICATION is used for notifications.
 *                      
 */
ipc_callid_t ipc_wait_cycle(ipc_call_t *call, uint32_t usec, int flags)
{
        ipc_callid_t callid;

        callid = __SYSCALL3(SYS_IPC_WAIT, (sysarg_t) call, usec, flags);
        /* Handle received answers */
        if (callid & IPC_CALLID_ANSWERED) {
                handle_answer(callid, call);
                try_dispatch_queued_calls();
        }

        return callid;
}

/** Wait some time for an IPC call.
 *
 * The call will return after an answer is received.
 *
 * @param call          Storage where the incoming call data will be stored.
 * @param usec          Timeout in microseconds.
 *
 * @return              Hash of the answer.
 */
ipc_callid_t ipc_wait_for_call_timeout(ipc_call_t *call, uint32_t usec)
{
        ipc_callid_t callid;

        do {
                callid = ipc_wait_cycle(call, usec, SYNCH_FLAGS_NONE);
        } while (callid & IPC_CALLID_ANSWERED);

        return callid;
}

/** Check if there is an IPC call waiting to be picked up.
 *
 * @param call          Storage where the incoming call will be stored.
 * @return              Hash of the answer.
 */
ipc_callid_t ipc_trywait_for_call(ipc_call_t *call)
{
        ipc_callid_t callid;

        do {
                callid = ipc_wait_cycle(call, SYNCH_NO_TIMEOUT,
                    SYNCH_FLAGS_NON_BLOCKING);
        } while (callid & IPC_CALLID_ANSWERED);

        return callid;
}

/** Ask destination to do a callback connection.
 *
 * @param phoneid       Phone handle used for contacting the other side.
 * @param arg1          Service-defined argument.
 * @param arg2          Service-defined argument.
 * @param arg3          Service-defined argument.
 * @param phonehash     Storage where the library will store an opaque
 *                      identifier of the phone that will be used for incoming
 *                      calls. This identifier can be used for connection
 *                      tracking.
 *
 * @return              Zero on success or a negative error code.
 */
int ipc_connect_to_me(int phoneid, int arg1, int arg2, int arg3, 
    ipcarg_t *phonehash)
{
        return ipc_call_sync_3_5(phoneid, IPC_M_CONNECT_TO_ME, arg1, arg2,
            arg3, NULL, NULL, NULL, NULL, phonehash);
}

/** Ask through phone for a new connection to some service.
 *
 * @param phoneid       Phone handle used for contacting the other side.
 * @param arg1          User defined argument.
 * @param arg2          User defined argument.
 * @param arg3          User defined argument.
 *
 * @return              New phone handle on success or a negative error code.
 */
int ipc_connect_me_to(int phoneid, int arg1, int arg2, int arg3)
{
        ipcarg_t newphid;
        int res;

        res = ipc_call_sync_3_5(phoneid, IPC_M_CONNECT_ME_TO, arg1, arg2, arg3, 
            NULL, NULL, NULL, NULL, &newphid);
        if (res)
                return res;
        return newphid;
}

/** Hang up a phone.
 *
 * @param phoneid       Handle of the phone to be hung up.
 *
 * @return              Zero on success or a negative error code.
 */
int ipc_hangup(int phoneid)
{
        return __SYSCALL1(SYS_IPC_HANGUP, phoneid);
}

/** Register IRQ notification.
 *
 * @param inr           IRQ number.
 * @param devno         Device number of the device generating inr.
 * @param method        Use this method for notifying me.
 * @param ucode         Top-half pseudocode handler.
 *
 * @return              Value returned by the kernel.
 */
int ipc_register_irq(int inr, int devno, int method, irq_code_t *ucode)
{
        return __SYSCALL4(SYS_IPC_REGISTER_IRQ, inr, devno, method,
            (sysarg_t) ucode);
}

/** Unregister IRQ notification.
 *
 * @param inr           IRQ number.
 * @param devno         Device number of the device generating inr.
 *
 * @return              Value returned by the kernel.
 */
int ipc_unregister_irq(int inr, int devno)
{
        return __SYSCALL2(SYS_IPC_UNREGISTER_IRQ, inr, devno);
}

/** Forward a received call to another destination.
 *
 * @param callid        Hash of the call to forward.
 * @param phoneid       Phone handle to use for forwarding.
 * @param method        New method for the forwarded call.
 * @param arg1          New value of the first argument for the forwarded call.
 * @param arg2          New value of the second argument for the forwarded call.
 * @param mode          Flags specifying mode of the forward operation.
 *
 * @return              Zero on success or an error code.
 *
 * For non-system methods, the old method, arg1 and arg2 are rewritten by the
 * new values. For system methods, the new method, arg1 and arg2 are written 
 * to the old arg1, arg2 and arg3, respectivelly. Calls with immutable 
 * methods are forwarded verbatim.
 */
int ipc_forward_fast(ipc_callid_t callid, int phoneid, int method,
    ipcarg_t arg1, ipcarg_t arg2, int mode)
{
        return __SYSCALL6(SYS_IPC_FORWARD_FAST, callid, phoneid, method, arg1, 
            arg2, mode);
}

/** Wrapper for making IPC_M_DATA_READ calls.
 *
 * @param phoneid       Phone that will be used to contact the receiving side.
 * @param dst           Address of the beginning of the destination buffer.
 * @param size          Size of the destination buffer.
 *
 * @return              Zero on success or a negative error code from errno.h.
 */
int ipc_data_read_send(int phoneid, void *dst, size_t size)
{
        return ipc_call_sync_2_0(phoneid, IPC_M_DATA_READ, (ipcarg_t) dst,
            (ipcarg_t) size);
}

/** Wrapper for receiving the IPC_M_DATA_READ calls.
 *
 * This wrapper only makes it more comfortable to receive IPC_M_DATA_READ calls
 * so that the user doesn't have to remember the meaning of each IPC argument.
 *
 * So far, this wrapper is to be used from within a connection fibril.
 *
 * @param callid        Storage where the hash of the IPC_M_DATA_READ call will
 *                      be stored.
 * @param size          Storage where the maximum size will be stored. Can be
 *                      NULL.
 *
 * @return              Non-zero on success, zero on failure.
 */
int ipc_data_read_receive(ipc_callid_t *callid, size_t *size)
{
        ipc_call_t data;
        
        assert(callid);

        *callid = async_get_call(&data);
        if (IPC_GET_METHOD(data) != IPC_M_DATA_READ)
                return 0;
        if (size)
                *size = (size_t) IPC_GET_ARG2(data);
        return 1;
}

/** Wrapper for answering the IPC_M_DATA_READ calls.
 *
 * This wrapper only makes it more comfortable to answer IPC_M_DATA_READ calls
 * so that the user doesn't have to remember the meaning of each IPC argument.
 *
 * @param callid        Hash of the IPC_M_DATA_READ call to answer.
 * @param src           Source address for the IPC_M_DATA_READ call.
 * @param size          Size for the IPC_M_DATA_READ call. Can be smaller than
 *                      the maximum size announced by the sender.
 *
 * @return              Zero on success or a value from @ref errno.h on failure.
 */
int ipc_data_read_deliver(ipc_callid_t callid, void *src, size_t size)
{
        return ipc_answer_2(callid, EOK, (ipcarg_t) src, (ipcarg_t) size);
}

/** Wrapper for making IPC_M_DATA_WRITE calls.
 *
 * @param phoneid       Phone that will be used to contact the receiving side.
 * @param src           Address of the beginning of the source buffer.
 * @param size          Size of the source buffer.
 *
 * @return              Zero on success or a negative error code from errno.h.
 */
int ipc_data_write_send(int phoneid, void *src, size_t size)
{
        return ipc_call_sync_3_0(phoneid, IPC_M_DATA_WRITE, 0, (ipcarg_t) src,
            (ipcarg_t) size);
}

/** Wrapper for receiving the IPC_M_DATA_WRITE calls.
 *
 * This wrapper only makes it more comfortable to receive IPC_M_DATA_WRITE calls
 * so that the user doesn't have to remember the meaning of each IPC argument.
 *
 * So far, this wrapper is to be used from within a connection fibril.
 *
 * @param callid        Storage where the hash of the IPC_M_DATA_WRITE call will
 *                      be stored.
 * @param dst           Storage where the suggested destination address will
 *                      be stored. May be NULL.
 * @param size          Storage where the suggested size will be stored. May be
 *                      NULL
 *
 * @return              Non-zero on success, zero on failure.
 */
int ipc_data_write_receive(ipc_callid_t *callid, void **dst, size_t *size)
{
        ipc_call_t data;
        
        assert(callid);

        *callid = async_get_call(&data);
        if (IPC_GET_METHOD(data) != IPC_M_DATA_WRITE)
                return 0;
        if (dst)
                *dst = (void *) IPC_GET_ARG1(data);
        if (size)
                *size = (size_t) IPC_GET_ARG3(data);
        return 1;
}

/** Wrapper for answering the IPC_M_DATA_WRITE calls.
 *
 * This wrapper only makes it more comfortable to answer IPC_M_DATA_WRITE calls
 * so that the user doesn't have to remember the meaning of each IPC argument.
 *
 * @param callid        Hash of the IPC_M_DATA_WRITE call to answer.
 * @param dst           Final destination address for the IPC_M_DATA_WRITE call.
 * @param size          Final size for the IPC_M_DATA_WRITE call.
 *
 * @return              Zero on success or a value from @ref errno.h on failure.
 */
int ipc_data_write_deliver(ipc_callid_t callid, void *dst, size_t size)
{
        return ipc_answer_3(callid, EOK, (ipcarg_t) dst, 0, (ipcarg_t) size);
}
 
/** @}
 */