260 lines
7.9 KiB
C
260 lines
7.9 KiB
C
/****************************************************************************
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* drivers/ipcc/ipcc_read.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <nuttx/ipcc.h>
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#include <nuttx/kmalloc.h>
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#include <nuttx/semaphore.h>
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#include <assert.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <sys/types.h>
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#include "ipcc_priv.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: ipcc_rxfree_notify
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*
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* Description:
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* Notifies all blocked threads or those waiting in poll/select that
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* there is data on buffer to perform reading.
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*
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* Input Parameters:
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* ipcc - pointer to driver instance
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*
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* Returned Value:
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* None
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*
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* Assumptions/Limitations:
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* This function can be called from interrupt handler from lower half.
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*
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****************************************************************************/
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void ipcc_rxfree_notify(FAR struct ipcc_driver_s *priv)
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{
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int semval;
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if (priv == NULL)
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{
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/* priv can be NULL when ipcc lower half is initialized but
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* upper half has not yet been initialized, and rx interrupt
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* has been received. In such case we don't wake any reader,
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* because since ipcc is not yet initialized there cannot be
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* any readers yet. We can safely return here, first read()
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* to this ipcc channel will immediately read data.
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*/
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return;
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}
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if ((nxsem_get_value(&priv->rxsem, &semval) == 0) && semval > 0)
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{
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/* Notify all poll/select waiters that they can read from the driver.
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* Do it only when there are no already blocked readers to avoid
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* situation where thread that is polling gets notified only to
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* be blocked in read() because another thread have read from
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* buffer before polling thread could.
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*/
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ipcc_pollnotify(priv, POLLIN);
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return;
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}
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/* Notify all blocked readers that data is available to read */
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while (nxsem_get_value(&priv->rxsem, &semval) >= 0 && semval <= 0)
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{
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nxsem_post(&priv->rxsem);
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}
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}
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/****************************************************************************
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* Name: ipcc_read
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*
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* Description:
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* Reads data from the IPCC lower driver. Will block if no data is
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* available, unless O_NONBLOCK flag is set.
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*
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* Input Parameters:
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* filep - file on vfs associated with the driver
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* buffer - buffer where read data should be copied to
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* buflen - size of the buffer... buffer
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*
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* Returned Value:
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* Will return number of bytes read or negated errno
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*
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* Assumptions/Limitations:
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*
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****************************************************************************/
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ssize_t ipcc_read(FAR struct file *filep, FAR char *buffer,
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size_t buflen)
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{
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FAR struct ipcc_driver_s *priv;
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ssize_t nread;
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int ret;
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int flags;
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/* Get our private data structure */
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priv = filep->f_inode->i_private;
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/* Get exclusive access to driver */
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if ((ret = nxmutex_lock(&priv->lock)))
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{
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/* nxsem_wait() will return on signal, we did not start
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* any transfer yet, so we can safely return with error
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*/
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return ret;
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}
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/* Disable interrupts, or we might get in situation when we:
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* - read 0 bytes from circbuf
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* - interrupt comes in
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* - it copies data to buffer and notifies blocked readers
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* (in this case sem count is 0, so no sem_post() is called)
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* - interrupt ends
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* - since we are in blocking mode, and we read 0 from buffer
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* we call sem_wait() and we hang in there cause rx interrupt
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* will not be triggered again.
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*/
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flags = enter_critical_section();
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for (; ; )
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{
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#ifdef CONFIG_IPCC_BUFFERED
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/* Data is buffered in interrupt handler, so we simply
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* have to return buffers content to the user
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*/
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if (circbuf_used(&priv->ipcc->rxbuf))
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{
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/* There is some data on buffer, we are sure we won't block
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* so immediately leave critical section to not block other
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* more important drivers
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*/
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leave_critical_section(flags);
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}
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if ((nread = circbuf_read(&priv->ipcc->rxbuf, buffer, buflen)) > 0)
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{
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/* got some data */
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if (priv->ipcc->overflow)
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{
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/* We tried to buffer data in previous interrupt, but
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* it failed due to rxbuf being full. Now that we took
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* some data from buffer, we can try to buffer data again
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*/
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priv->ipcc->ops.buffer_data(priv->ipcc, &priv->ipcc->rxbuf);
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if ((size_t)nread < buflen)
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{
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/* There is still some space left on buffer, and
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* we just added new data to buffer, get more data
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* for the user
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*/
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nread += circbuf_read(&priv->ipcc->rxbuf, buffer + nread,
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buflen - nread);
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}
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}
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/* return number of bytes read to the caller */
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nxmutex_unlock(&priv->lock);
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return nread;
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}
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#else /* CONFIG_IPCC_BUFFERED */
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/* Unbuffered read, read data directly from lower driver */
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if ((nread = priv->ipcc->ops.read(priv->ipcc, buffer, buflen)) != 0)
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{
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/* Got some data, return number of bytes read to the caller
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* --or--
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* read() returned error in which case return errno value
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*/
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leave_critical_section(flags);
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nxmutex_unlock(&priv->lock);
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return nread;
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}
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#endif /* CONFIG_IPCC_BUFFERED */
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/* no data on the buffer, should we block? */
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if (filep->f_oflags & O_NONBLOCK)
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{
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/* No, we should not block, so inform caller that
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* no data could be read
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*/
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leave_critical_section(flags);
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nxmutex_unlock(&priv->lock);
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return -EAGAIN;
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}
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/* We are in blocking mode, so we have to wait for data to arrive.
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*/
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nxmutex_unlock(&priv->lock);
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if ((ret = nxsem_wait(&priv->rxsem)))
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{
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leave_critical_section(flags);
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/* We were interrupted by signal, but we have not written
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* any data to caller's buffer, so we return with error
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*/
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return ret;
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}
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/* Data should now be available, but it's possible that
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* another thread will read all data from buffer before
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* we can do it, so we will stay in the loop until we
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* manage to read something - or interrupt signal occurs
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*
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* We have released exclusive lock to driver when we were
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* waiting for data, so now let's retake it.
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*/
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nxmutex_lock(&priv->lock);
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}
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leave_critical_section(flags);
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}
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