/****************************************************************************
* drivers/ramlog.c
*
* Copyright (C) 2012 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 <sys/ioctl.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/fs.h>
#include <nuttx/kmalloc.h>
#include <nuttx/fs.h>
#include <nuttx/arch.h>
#include <nuttx/ramlog.h>
#include <arch/irq.h>
#ifdef CONFIG_RAMLOG
/****************************************************************************
* Private Types
****************************************************************************/
/****************************************************************************
* Private Types
****************************************************************************/
struct ramlog_dev_s
{
volatile uint8_t rl_nwaiters; /* Number of threads waiting for data */
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 */
sem_t rl_waitsem; /* Used to wait for data */
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'.
*/
#ifndef CONFIG_DISABLE_POLL
struct pollfd *rl_fds[CONFIG_RAMLOG_NPOLLWAITERS];
#endif
};
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
static ssize_t ramlog_read(FAR struct file *, FAR char *, size_t);
static ssize_t ramlog_write(FAR struct file *, FAR const char *, size_t);
#ifndef CONFIG_DISABLE_POLL
static int ramlog_poll(FAR struct file *filep, FAR struct pollfd *fds,
bool setup);
#endif
/****************************************************************************
* Private Data
****************************************************************************/
static const struct file_operations g_ramlogfops =
{
0, /* open */
0, /* close */
ramlog_read, /* read */
ramlog_write, /* write */
0, /* seek */
0 /* ioctl */
#ifndef CONFIG_DISABLE_POLL
, ramlog_poll /* poll */
#endif
};
/* This is the pre-allocated buffer used for the console RAM log */
#ifdef CONFIG_RAMLOG_CONSOLE
static char g_consoleramlog[CONFIG_RAMLOG_CONSOLE_BUFSIZE];
#endif
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: ramlog_pollnotify
****************************************************************************/
#ifndef CONFIG_DISABLE_POLL
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 = irqsave();
fds = priv->rl_fds[i];
if (fds)
{
fds->revents |= (fds->events & eventset);
if (fds->revents != 0)
{
sem_post(fds->sem);
}
}
irqrestore(flags);
}
}
#else
# define ramlog_pollnotify(priv,event)
#endif
/****************************************************************************
* Name: ramlog_read
****************************************************************************/
static ssize_t ramlog_read(FAR struct file *filep, FAR char *buffer, size_t len)
{
struct inode *inode = filep->f_inode;
struct ramlog_dev_s *priv;
ssize_t nread;
char ch;
int ret;
/* Some sanity checking */
DEBUGASSERT(inode && inode->i_private);
priv = 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 = sem_wait(&priv->rl_exclsem);
if (ret < 0)
{
return ret;
}
/* Loop until something is read */
for (nread = 0; nread < len; )
{
/* Get the next byte from the buffer */
if (priv->rl_head == priv->rl_tail)
{
/* The circular buffer is empty. Did we read anything? */
if (nread > 0)
{
/* Yes.. re-enable interrupts and the break out to return what
* we have.
*/
break;
}
/* If the driver was opened with O_NONBLOCK option, then don't wait.
* Re-enable interrupts and return EGAIN.
*/
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 not that it needs to post the semaphore to wake us up.
*/
sched_lock();
priv->rl_nwaiters++;
sem_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 = sem_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 = sem_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 sem_wait's failed. */
int errval = errno;
/* Were we awakened by a signal? Did we read anything before
* we received the signal?
*/
if (errval != EINTR || nread >= 0)
{
/* Yes.. return the error. */
nread = -errval;
}
/* 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;
}
}
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 and re-enable interrupts */
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 */
sem_post(&priv->rl_exclsem);
/* Notify all poll/select waiters that they can write to the FIFO */
errout_without_sem:
if (nread > 0)
{
ramlog_pollnotify(priv, POLLOUT);
}
return nread;
}
/****************************************************************************
* Name: ramlog_write
****************************************************************************/
static ssize_t ramlog_write(FAR struct file *filep, FAR const char *buffer, size_t len)
{
struct inode *inode = filep->f_inode;
struct ramlog_dev_s *priv;
irqstate_t flags;
ssize_t nwritten;
int nexthead;
int i;
/* Some sanity checking */
DEBUGASSERT(inode && inode->i_private);
priv = 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_tail is protected by disabling
* interrupts.
*/
for (nwritten = 0; nwritten < len; nwritten++)
{
/* Disable interrupts (in case we are NOT called from interrupt handler) */
flags = irqsave();
/* 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)
{
/* Yes... then break out of the loop to return the number of bytes
* written. The data to be written is dropped on the floor.
*/
return nwritten;
}
/* No... copy the byte and re-enable interrupts */
priv->rl_buffer[priv->rl_head] = buffer[nwritten];
priv->rl_head = nexthead;
irqrestore(flags);
}
/* Was anything written? */
if (nwritten > 0)
{
/* Are there threads waiting for read data? */
flags = irqsave();
for (i = 0; i < priv->rl_nwaiters; i++)
{
/* Yes.. Notify all of the waiting readers that more data is available */
sem_post(&priv->rl_waitsem);
}
/* Notify all poll/select waiters that they can write to the FIFO */
ramlog_pollnotify(priv, POLLIN);
}
/* Return the number of bytes written */
return nwritten;
}
/****************************************************************************
* Name: ramlog_poll
****************************************************************************/
#ifndef CONFIG_DISABLE_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;
int ndx;
int ret;
int i;
/* Some sanity checking */
DEBUGASSERT(inode && inode->i_private);
priv = inode->i_private;
/* Get exclusive access to the poll structures */
ret = sem_wait(&priv->rl_exclsem);
if (ret < 0)
{
int errval = errno;
return -errval;
}
/* 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?
* First, check if the xmit buffer is full.
*/
eventset = 0;
ndx = priv->rl_head + 1;
if (ndx >= priv->rl_bufsize)
{
ndx = 0;
}
if (ndx != priv->rl_tail)
{
eventset |= POLLOUT;
}
/* Check if the receive buffer is empty */
if (priv->rl_head != priv->rl_tail)
{
eventset |= POLLIN;
}
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
if (!slot)
{
ret = -EIO;
goto errout;
}
#endif
/* Remove all memory of the poll setup */
*slot = NULL;
fds->priv = NULL;
}
errout:
sem_post(&priv->rl_exclsem);
return ret;
}
#endif
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: ramlog_register
*
* Description:
* Create the RAM logging device and register it at the specified path.
* Mostly likely this path will be /dev/console
*
****************************************************************************/
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 *)kzalloc(sizeof(struct ramlog_dev_s));
if (priv)
{
/* Initialize the non-zero values in the RAM logging device structure */
sem_init(&priv->rl_exclsem, 0, 1);
sem_init(&priv->rl_waitsem, 0, 0);
priv->rl_bufsize = buflen;
priv->rl_buffer = buffer;
/* Register the character driver */
ret = register_driver(devpath, &g_ramlogfops, 0666, priv);
if (ret < 0)
{
kfree(priv);
}
}
return ret;
}
/****************************************************************************
* Name: ramlog_consoleinit
*
* Description:
* Create the RAM logging device and register it at the specified path.
* Mostly likely this path will be /dev/console
*
****************************************************************************/
#ifdef CONFIG_RAMLOG_CONSOLE
int ramlog_consoleinit(void)
{
/* Register a RAM log as the console device */
return ramlog_register("/dev/console", g_consoleramlog,
CONFIG_RAMLOG_CONSOLE_BUFSIZE);
}
#endif
/****************************************************************************
* Name: ramlog
*
* Description:
* This is the low-level system logging interface. The debugging/syslogging
* interfaces are lib_rawprintf() and lib_lowprinf(). The difference is
* the lib_rawprintf() writes to fd=1 (stdout) and lib_lowprintf() uses
* a lower level interface that works from interrupt handlers. This
* function is a a low-level interface used to implement lib_lowprintf()
* when CONFIG_RAMLOG_SYSLOG=y and CONFIG_SYSLOG=ramlog
*
****************************************************************************/
#ifdef CONFIG_RAMLOG_SYSLOG
# warning "Missing logic"
#endif
#endif /* CONFIG_RAMLOG */
