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incubator-nuttx/drivers/syslog/ramlog.c

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/****************************************************************************
* drivers/syslog/ramlog.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <stdio.h>
#include <stdint.h>
#include <stdbool.h>
#include <stdlib.h>
#include <fcntl.h>
#include <string.h>
#include <poll.h>
#include <errno.h>
#include <assert.h>
#include <debug.h>
#include <nuttx/arch.h>
#include <nuttx/kmalloc.h>
#include <nuttx/semaphore.h>
#include <nuttx/fs/fs.h>
#include <nuttx/syslog/ramlog.h>
#include <nuttx/irq.h>
#ifdef CONFIG_RAMLOG
/****************************************************************************
* Private Types
****************************************************************************/
struct ramlog_dev_s
{
#ifndef CONFIG_RAMLOG_NONBLOCKING
volatile uint8_t rl_nwaiters; /* Number of threads waiting for data */
#endif
volatile uint16_t rl_head; /* The head index (where data is added) */
volatile uint16_t rl_tail; /* The tail index (where data is removed) */
sem_t rl_exclsem; /* Enforces mutually exclusive access */
#ifndef CONFIG_RAMLOG_NONBLOCKING
sem_t rl_waitsem; /* Used to wait for data */
#endif
size_t rl_bufsize; /* Size of the RAM buffer */
FAR char *rl_buffer; /* Circular RAM buffer */
/* The following is a list if poll structures of threads waiting for
* driver events. The 'struct pollfd' reference for each open is also
* retained in the f_priv field of the 'struct file'.
*/
FAR struct pollfd *rl_fds[CONFIG_RAMLOG_NPOLLWAITERS];
};
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
/* Helper functions */
#ifndef CONFIG_RAMLOG_NONBLOCKING
static int ramlog_readnotify(FAR struct ramlog_dev_s *priv);
#endif
static void ramlog_pollnotify(FAR struct ramlog_dev_s *priv,
pollevent_t eventset);
static ssize_t ramlog_addchar(FAR struct ramlog_dev_s *priv, char ch);
/* Character driver methods */
static ssize_t ramlog_read(FAR struct file *filep, FAR char *buffer,
size_t buflen);
static ssize_t ramlog_write(FAR struct file *filep, FAR const char *buffer,
size_t buflen);
static int ramlog_poll(FAR struct file *filep, FAR struct pollfd *fds,
bool setup);
/****************************************************************************
* Private Data
****************************************************************************/
static const struct file_operations g_ramlogfops =
{
NULL, /* open */
NULL, /* close */
ramlog_read, /* read */
ramlog_write, /* write */
NULL, /* seek */
NULL, /* ioctl */
ramlog_poll /* poll */
#ifndef CONFIG_DISABLE_PSEUDOFS_OPERATIONS
, NULL /* unlink */
#endif
};
/* This is the pre-allocated buffer used for the console RAM log and/or
* for the syslogging function.
*/
#ifdef CONFIG_RAMLOG_SYSLOG
static char g_sysbuffer[CONFIG_RAMLOG_BUFSIZE];
/* This is the device structure for the console or syslogging function. It
* must be statically initialized because the RAMLOG ramlog_putc function
* could be called before the driver initialization logic executes.
*/
static struct ramlog_dev_s g_sysdev =
{
#ifndef CONFIG_RAMLOG_NONBLOCKING
0, /* rl_nwaiters */
#endif
0, /* rl_head */
0, /* rl_tail */
SEM_INITIALIZER(1), /* rl_exclsem */
#ifndef CONFIG_RAMLOG_NONBLOCKING
SEM_INITIALIZER(0), /* rl_waitsem */
#endif
CONFIG_RAMLOG_BUFSIZE, /* rl_bufsize */
g_sysbuffer /* rl_buffer */
};
#endif
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: ramlog_readnotify
****************************************************************************/
#ifndef CONFIG_RAMLOG_NONBLOCKING
static int ramlog_readnotify(FAR struct ramlog_dev_s *priv)
{
irqstate_t flags;
int i;
/* Notify all waiting readers that they can read from the FIFO */
flags = enter_critical_section();
for (i = 0; i < priv->rl_nwaiters; i++)
{
nxsem_post(&priv->rl_waitsem);
}
leave_critical_section(flags);
/* Return number of notified readers. */
return i;
}
#endif
/****************************************************************************
* Name: ramlog_pollnotify
****************************************************************************/
static void ramlog_pollnotify(FAR struct ramlog_dev_s *priv,
pollevent_t eventset)
{
FAR struct pollfd *fds;
irqstate_t flags;
int i;
/* This function may be called from an interrupt handler */
for (i = 0; i < CONFIG_RAMLOG_NPOLLWAITERS; i++)
{
flags = enter_critical_section();
fds = priv->rl_fds[i];
if (fds)
{
fds->revents |= (fds->events & eventset);
if (fds->revents != 0)
{
nxsem_post(fds->sem);
}
}
leave_critical_section(flags);
}
}
/****************************************************************************
* Name: ramlog_addchar
****************************************************************************/
static ssize_t ramlog_addchar(FAR struct ramlog_dev_s *priv, char ch)
{
irqstate_t flags;
size_t nexthead;
/* Disable interrupts (in case we are NOT called from interrupt handler) */
flags = enter_critical_section();
/* Calculate the write index AFTER the next byte is written */
nexthead = priv->rl_head + 1;
if (nexthead >= priv->rl_bufsize)
{
nexthead = 0;
}
/* Would the next write overflow the circular buffer? */
if (nexthead == priv->rl_tail)
{
#ifdef CONFIG_RAMLOG_OVERWRITE
/* Yes... Overwrite with the latest log in the circular buffer */
priv->rl_tail += 1;
if (priv->rl_tail >= priv->rl_bufsize)
{
priv->rl_tail = 0;
}
#else
/* Yes... Return an indication that nothing was saved in the buffer. */
leave_critical_section(flags);
return -EBUSY;
#endif
}
/* No... copy the byte and re-enable interrupts */
priv->rl_buffer[priv->rl_head] = ch;
priv->rl_head = nexthead;
leave_critical_section(flags);
return OK;
}
/****************************************************************************
* Name: ramlog_read
****************************************************************************/
static ssize_t ramlog_read(FAR struct file *filep, FAR char *buffer,
size_t len)
{
FAR struct inode *inode = filep->f_inode;
FAR struct ramlog_dev_s *priv;
ssize_t nread;
char ch;
int ret;
/* Some sanity checking */
DEBUGASSERT(inode && inode->i_private);
priv = (FAR struct ramlog_dev_s *)inode->i_private;
/* If the circular buffer is empty, then wait for something to be written
* to it. This function may NOT be called from an interrupt handler.
*/
DEBUGASSERT(!up_interrupt_context());
/* Get exclusive access to the rl_tail index */
ret = nxsem_wait(&priv->rl_exclsem);
if (ret < 0)
{
return ret;
}
/* Loop until something is read */
for (nread = 0; (size_t)nread < len; )
{
/* Get the next byte from the buffer */
if (priv->rl_head == priv->rl_tail)
{
/* The circular buffer is empty. */
#ifdef CONFIG_RAMLOG_NONBLOCKING
/* Return what we have (with zero mean the end-of-file) */
break;
#else
/* Did we read anything? */
if (nread > 0)
{
/* Yes.. break out to return what we have. */
break;
}
/* If the driver was opened with O_NONBLOCK option, then don't
* wait.
*/
if (filep->f_oflags & O_NONBLOCK)
{
nread = -EAGAIN;
break;
}
/* Otherwise, wait for something to be written to the circular
* buffer. Increment the number of waiters so that the
* ramlog_write() will note that it needs to post the semaphore
* to wake us up.
*/
sched_lock();
priv->rl_nwaiters++;
nxsem_post(&priv->rl_exclsem);
/* We may now be pre-empted! But that should be okay because we
* have already incremented nwaiters. Pre-emptions is disabled
* but will be re-enabled while we are waiting.
*/
ret = nxsem_wait(&priv->rl_waitsem);
/* Interrupts will be disabled when we return. So the decrementing
* rl_nwaiters here is safe.
*/
priv->rl_nwaiters--;
sched_unlock();
/* Did we successfully get the rl_waitsem? */
if (ret >= 0)
{
/* Yes... then retake the mutual exclusion semaphore */
ret = nxsem_wait(&priv->rl_exclsem);
}
/* Was the semaphore wait successful? Did we successful re-take the
* mutual exclusion semaphore?
*/
if (ret < 0)
{
/* No.. One of the two nxsem_wait's failed. */
/* Return the error. We did handle the case where we read
* anything already before waiting.
*/
nread = ret;
/* Break out to return what we have. Note, we can't exactly
* "break" out because whichever error occurred, we do not hold
* the exclusion semaphore.
*/
goto errout_without_sem;
}
#endif /* CONFIG_RAMLOG_NONBLOCKING */
}
else
{
/* The circular buffer is not empty, get the next byte from the
* tail index.
*/
ch = priv->rl_buffer[priv->rl_tail];
/* Increment the tail index. */
if (++priv->rl_tail >= priv->rl_bufsize)
{
priv->rl_tail = 0;
}
/* Add the character to the user buffer. */
buffer[nread] = ch;
nread++;
}
}
/* Relinquish the mutual exclusion semaphore */
nxsem_post(&priv->rl_exclsem);
/* Notify all poll/select waiters that they can write to the FIFO */
#ifndef CONFIG_RAMLOG_NONBLOCKING
errout_without_sem:
#endif
if (nread > 0)
{
ramlog_pollnotify(priv, POLLOUT);
}
/* Return the number of characters actually read */
return nread;
}
/****************************************************************************
* Name: ramlog_write
****************************************************************************/
static ssize_t ramlog_write(FAR struct file *filep, FAR const char *buffer,
size_t len)
{
FAR struct inode *inode = filep->f_inode;
FAR struct ramlog_dev_s *priv;
int readers_waken;
ssize_t nwritten;
char ch;
int ret;
/* Some sanity checking */
DEBUGASSERT(inode && inode->i_private);
priv = (FAR struct ramlog_dev_s *)inode->i_private;
/* Loop until all of the bytes have been written. This function may be
* called from an interrupt handler! Semaphores cannot be used!
*
* The write logic only needs to modify the rl_head index. Therefore,
* there is a difference in the way that rl_head and rl_tail are protected:
* rl_tail is protected with a semaphore; rl_head is protected by disabling
* interrupts.
*/
for (nwritten = 0; (size_t)nwritten < len; nwritten++)
{
/* Get the next character to output */
ch = buffer[nwritten];
/* Ignore carriage returns */
#ifdef CONFIG_RAMLOG_CRLF
if (ch == '\r')
{
continue;
}
/* Pre-pend a carriage before a linefeed */
if (ch == '\n')
{
ret = ramlog_addchar(priv, '\r');
if (ret < 0)
{
/* The buffer is full and nothing was saved. The remaining
* data to be written is dropped on the floor.
*/
break;
}
}
#endif
/* Then output the character */
ret = ramlog_addchar(priv, ch);
if (ret < 0)
{
/* The buffer is full and nothing was saved. The remaining
* data to be written is dropped on the floor.
*/
break;
}
}
/* Was anything written? */
if (nwritten > 0)
{
readers_waken = 0;
#ifndef CONFIG_RAMLOG_NONBLOCKING
/* Are there threads waiting for read data? */
readers_waken = ramlog_readnotify(priv);
#endif
/* If there are multiple readers, some of them might block despite
* POLLIN because first reader might read all data. Favor readers
* and notify poll waiters only if no reader was awaken, even if the
* latter may starve.
*
* This also implies we do not have to make these two notify
* operations a critical section.
*/
if (readers_waken == 0)
{
/* Notify all poll/select waiters that they can read from the
* FIFO.
*/
ramlog_pollnotify(priv, POLLIN);
}
}
/* We always have to return the number of bytes requested and NOT the
* number of bytes that were actually written. Otherwise, callers
* probably retry, causing same error condition again.
*/
return len;
}
/****************************************************************************
* Name: ramlog_poll
****************************************************************************/
int ramlog_poll(FAR struct file *filep, FAR struct pollfd *fds, bool setup)
{
FAR struct inode *inode = filep->f_inode;
FAR struct ramlog_dev_s *priv;
pollevent_t eventset;
irqstate_t flags;
size_t next_head;
int ret;
int i;
/* Some sanity checking */
DEBUGASSERT(inode && inode->i_private);
priv = (FAR struct ramlog_dev_s *)inode->i_private;
/* Get exclusive access to the poll structures */
ret = nxsem_wait(&priv->rl_exclsem);
if (ret < 0)
{
return ret;
}
/* Are we setting up the poll? Or tearing it down? */
if (setup)
{
/* This is a request to set up the poll. Find an available
* slot for the poll structure reference.
*/
for (i = 0; i < CONFIG_RAMLOG_NPOLLWAITERS; i++)
{
/* Find an available slot */
if (!priv->rl_fds[i])
{
/* Bind the poll structure and this slot */
priv->rl_fds[i] = fds;
fds->priv = &priv->rl_fds[i];
break;
}
}
if (i >= CONFIG_RAMLOG_NPOLLWAITERS)
{
fds->priv = NULL;
ret = -EBUSY;
goto errout;
}
/* Should immediately notify on any of the requested events? */
eventset = 0;
flags = enter_critical_section();
next_head = priv->rl_head + 1;
if (next_head >= priv->rl_bufsize)
{
next_head = 0;
}
/* First, check if the receive buffer is not full. */
if (next_head != priv->rl_tail)
{
eventset |= POLLOUT;
}
/* Check if the receive buffer is not empty. */
if (priv->rl_head != priv->rl_tail)
{
eventset |= POLLIN;
}
leave_critical_section(flags);
if (eventset)
{
ramlog_pollnotify(priv, eventset);
}
}
else if (fds->priv)
{
/* This is a request to tear down the poll. */
struct pollfd **slot = (struct pollfd **)fds->priv;
#ifdef CONFIG_DEBUG_FEATURES
if (!slot)
{
ret = -EIO;
goto errout;
}
#endif
/* Remove all memory of the poll setup */
*slot = NULL;
fds->priv = NULL;
}
errout:
nxsem_post(&priv->rl_exclsem);
return ret;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: ramlog_register
*
* Description:
* Create the RAM logging device and register it at the specified path.
*
****************************************************************************/
int ramlog_register(FAR const char *devpath, FAR char *buffer, size_t buflen)
{
FAR struct ramlog_dev_s *priv;
int ret = -ENOMEM;
/* Sanity checking */
DEBUGASSERT(devpath && buffer && buflen > 1);
/* Allocate a RAM logging device structure */
priv = (struct ramlog_dev_s *)kmm_zalloc(sizeof(struct ramlog_dev_s));
if (priv != NULL)
{
/* Initialize the non-zero values in the RAM logging device structure */
nxsem_init(&priv->rl_exclsem, 0, 1);
#ifndef CONFIG_RAMLOG_NONBLOCKING
nxsem_init(&priv->rl_waitsem, 0, 0);
/* The rl_waitsem semaphore is used for signaling and, hence, should
* not have priority inheritance enabled.
*/
nxsem_set_protocol(&priv->rl_waitsem, SEM_PRIO_NONE);
#endif
priv->rl_bufsize = buflen;
priv->rl_buffer = buffer;
/* Register the character driver */
ret = register_driver(devpath, &g_ramlogfops, 0666, priv);
if (ret < 0)
{
kmm_free(priv);
}
}
return ret;
}
/****************************************************************************
* Name: ramlog_syslog_register
*
* Description:
* Use a pre-allocated RAM logging device and register it at the path
* specified by CONFIG_RAMLOG_SYSLOG
*
****************************************************************************/
#ifdef CONFIG_RAMLOG_SYSLOG
void ramlog_syslog_register(void)
{
/* Register the syslog character driver */
register_driver(CONFIG_SYSLOG_DEVPATH, &g_ramlogfops, 0666, &g_sysdev);
}
#endif
/****************************************************************************
* Name: ramlog_putc
*
* Description:
* This is the low-level system logging interface.
*
****************************************************************************/
#ifdef CONFIG_RAMLOG_SYSLOG
int ramlog_putc(int ch)
{
FAR struct ramlog_dev_s *priv = &g_sysdev;
int readers_waken = 0;
int ret;
#ifdef CONFIG_RAMLOG_CRLF
/* Ignore carriage returns. But return success. */
if (ch == '\r')
{
return ch;
}
/* Pre-pend a newline with a carriage return */
if (ch == '\n')
{
ret = ramlog_addchar(priv, '\r');
if (ret < 0)
{
/* The buffer is full and nothing was saved. */
return ret;
}
}
#endif
/* Add the character to the RAMLOG */
ret = ramlog_addchar(priv, ch);
if (ret < 0)
{
/* The buffer is full and 'ch' was not saved. */
return ret;
}
#ifndef CONFIG_RAMLOG_NONBLOCKING
/* Are there threads waiting for read data? */
readers_waken = ramlog_readnotify(priv);
#endif
/* If there are multiple readers, some of them might block despite
* POLLIN because first reader might read all data. Favor readers
* and notify poll waiters only if no reader was awaken, even if the
* latter may starve.
*
* This also implies we do not have to make these two notify
* operations a critical section.
*/
if (readers_waken == 0)
{
/* Notify all poll/select waiters that they can read from the FIFO */
ramlog_pollnotify(priv, POLLIN);
}
/* Return the character added on success */
return ch;
}
#endif
#endif /* CONFIG_RAMLOG */
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