nuttx/drivers/syslog/note_driver.c

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/****************************************************************************
* drivers/syslog/note_driver.c
*
* Copyright (C) 2016 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "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
* COPYRIGHT OWNER OR CONTRIBUTORS 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.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <sched.h>
#include <assert.h>
#include <errno.h>
#include <nuttx/sched_note.h>
#include <nuttx/fs/fs.h>
#if defined(CONFIG_SCHED_INSTRUMENTATION_BUFFER) && \
defined(CONFIG_DRIVER_NOTE)
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
static ssize_t note_read(FAR struct file *filep, FAR char *buffer,
size_t buflen);
/****************************************************************************
* Private Data
****************************************************************************/
static const struct file_operations note_fops =
{
NULL, /* open */
NULL, /* close */
note_read, /* read */
NULL, /* write */
NULL, /* seek */
NULL, /* ioctl */
NULL /* poll */
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
, 0 /* unlink */
#endif
};
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: note_read
****************************************************************************/
static ssize_t note_read(FAR struct file *filep, FAR char *buffer,
size_t buflen)
{
ssize_t notelen;
ssize_t retlen ;
DEBUGASSERT(filep != 0 && buffer != NULL && buflen > 0);
/* Then loop, adding as many notes as possible to the user buffer. */
retlen = 0;
sched_lock();
do
{
/* Get the next note (removing it from the buffer) */
notelen = sched_note_get((FAR uint8_t *)buffer, buflen);
if (notelen < 0)
{
/* We were unable to read the next note, probably because it will
* not fit into the user buffer.
*/
if (retlen == 0)
{
/* If nothing was read then report the error. Otherwise,
* just silently drop the note.
*/
retlen = notelen;
}
break;
}
/* Update pointers from the note that was transferred */
retlen += notelen;
buffer += notelen;
buflen -= notelen;
/* Will the next note fit? There is a race here and even if the next
* note will fit, it may fail still when sched_note_get() is called.
*
* It won't fit (or an error occurred). Return what we have without
* trying to get the next note (which would cause it to be deleted).
*/
notelen = sched_note_size();
}
while (notelen > 0 && notelen <= buflen);
sched_unlock();
return retlen;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: note_register
*
* Description:
* Register a serial driver at /dev/note that can be used by an
* application to read data from the circular note buffer.
*
* Input Parameters:
* None.
*
* Returned Value:
* Zero is returned if the circular buffer is empty. Otherwise, a negated
* errno value is returned.
*
****************************************************************************/
int note_register(void)
{
return register_driver("/dev/note", &note_fops, 0666, NULL);
}
#endif /* CONFIG_SCHED_INSTRUMENTATION_BUFFER && CONFIG_DRIVER_NOTE */