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    /****************************************************************************
   * Name: syslog and

 vsyslog
   *
   * Description:
   *   syslog() generates a log message. The priority argument is formed

 by
   *   ORing the facility and the level values (see include/syslog.h).

 The
   *   remaining arguments are a format, as in printf and any arguments to the
   *   format.
   *
   *   The NuttX implementation does not support any special formatting
   *   characters beyond those supported by printf.
   *
   *   The function vsyslog() performs the same task as syslog() with the
   *   difference that it takes a set of arguments which have been obtained
   *   using the stdarg variable argument list macros.
   *
   ****************************************************************************/

    /****************************************************************************
   * Name:

 setlogmask
   *
   * Description:
   *   The setlogmask() function sets the logmask and returns the

 previous
   *   mask. If the mask argument is 0, the current logmask is not modified.

   *
   *   The SYSLOG priorities are: LOG_EMERG, LOG_ALERT, LOG_CRIT, LOG_ERR,

   *   LOG_WARNING, LOG_NOTICE, LOG_INFO, and LOG_DEBUG.  The bit

 corresponding
   *   to a priority p is LOG_MASK(p); LOG_UPTO(p) provides the mask of

 all
   *   priorities in the above list up to and including p.
   *
   *   Per OpenGroup.org "If the maskpri argument is 0, the current log mask
   *   is not modified."  In this implementation, the value zero is permitted
   *   in order to disable all syslog levels.
   *
   *   REVISIT: Per POSIX the syslog mask should be a per-process value but in
   *   NuttX, the scope of the mask is dependent on the nature of the build:
   *
   *   Flat Build:  There is one, global SYSLOG mask that controls all output.
   *   Protected Build:  There are two SYSLOG masks.  One within the kernel
   *     that controls only kernel output.  And one in user-space that controls
   *     only user SYSLOG output.
   *   Kernel Build:  The kernel build is compliant with the POSIX requirement:
   *     There will be one mask for for each user process, controlling the
   *     SYSLOG output only form that process.  There will be a separate mask
   *     accessable only in the kernel code to control kernel SYSLOG output.
   *
   ****************************************************************************/

    /****************************************************************************
* Name: syslog_channel

*
* Description:

* Configure the SYSLOGging function to use the provided channel to

* generate SYSLOG output.

*
* Input Parameters:

* channel - Provides the interface to the channel to be used.

*
* Returned Value:

* Zero (OK)is returned on success. A negated errno value is returned

* on any failure.

*
****************************************************************************/

    /****************************************************************************
   * Name: syslog_initialize

   *
   * Description:
   *   One power up, the SYSLOG facility is non-existent or limited to very
   *   low-level output.  This function is called later in the initialization
   *   sequence after full driver support has been initialized.  It installs
   *   the configured SYSLOG drivers and enables full SYSLOGing capability.
   *
   *   This function performs these basic operations:
   *
   *   - Initialize the SYSLOG device
   *   - Call syslog_channel() to begin using that device.
   *
   *   If CONFIG_ARCH_SYSLOG is selected, then the architecture-specific
   *   logic will provide its own SYSLOG device initialize which must include
   *   as a minimum a call to syslog_channel() to use the device.
   *
   * Input Parameters:
   *   phase - One of {SYSLOG_INIT_EARLY, SYSLOG_INIT_LATE}

   *
   * Returned Value:
   *   Zero (OK) is returned on success; a negated errno value is returned

 on
   *   any failure.
   *
   ****************************************************************************/

    /****************************************************************************
   * Name: syslog_file_channel

   *
   * Description:
   *   Configure to use a file in a mounted file system at 'devpath' as the
   *   SYSLOG channel.
   *
   *   This tiny function is simply a wrapper around syslog_dev_initialize()

   *   and syslog_channel().  It calls syslog_dev_initialize() to

 configure
   *   the character file at 'devpath then calls syslog_channel() to use

 that
   *   device as the SYSLOG output channel.
   *
   *   File SYSLOG channels differ from other SYSLOG channels in that they
   *   cannot be established until after fully booting and mounting the target
   *   file system.  This function would need to be called from board-specific
   *   bring-up logic AFTER mounting the file system containing 'devpath'.
   *
   *   SYSLOG data generated prior to calling syslog_file_channel will, of
   *   course, not be included in the file.
   *
   *   NOTE interrupt level SYSLOG output will be lost in this case unless
   *   the interrupt buffer is used.
   *
   * Input Parameters:
   *   devpath - The full path to the file to be used for SYSLOG output.
   *     This may be an existing file or not.  If the file exists,
   *     syslog_file_channel() will append new SYSLOG data to the end of

 the
   *     file.  If it does not, then syslog_file_channel() will create

 the
   *     file.
   *
   * Returned Value:
   *   Zero (OK) is returned on success; a negated errno value is returned on
   *   any failure.
   *
   ****************************************************************************/

    /****************************************************************************
   * Name: syslog_register

   *
   * Description:
   *   Register a simple character driver at /dev/syslog whose write()

 method
   *   will transfer data to the SYSLOG device.  This can be useful if, for
   *   example, you want to redirect the output of a program to the SYSLOG.
   *
   *   NOTE that unlike other syslog output, this data is unformatted raw
   *   byte output with no time-stamping or any other SYSLOG features
   *   supported.
   *
   ****************************************************************************/