Last Updated: May 12, 2016
+Last Updated: June 22, 2016
@@ -208,11 +208,18 @@ 6.3.8 USB Host-Side Driversinclude/syslog.h. The primary interface to SYSLOG sub-system
+ is the function syslog() and, to a lesser extent, its companion vsyslog():
+
+syslog() and vsyslog()Function Prototypes:
++int syslog(int priority, FAR const IPTR char *format, ...); +int vsyslog(int priority, FAR const IPTR char *src, va_list ap); ++
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.
+
setlogmask()
+ The additional setlogmask() interface can use use to filter SYSLOG output:
+
Function Prototype:
++int setlogmask(int mask); ++
Description:
+ The setlogmask() function sets the logmask and returns the previous mask. If the mask argument is zerio, 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. +
+ These are all standard interfaces as defined at OpenGroup.org. +
+ +
+ In NuttX, syslog output is really synonymous to debug output and, herefore, the debugging interface macros defined in the header file
+ include/debug.h are also syslogging interfaces. Those macros are simply wrappers around syslog(). The debugging interfaces differ from the syslog interfaces in that:
+
+ They do not take a priority parameter; the priority is inherent in the + debug macro name. +
+ They decorate the output stream with information such as the file name +
+ They can each be disabled via configuration options. +
+ Each debug macro has a base name that represents the priority and a prefix that represents the sub-system. Each macro is individually initialized by both priority and sub-system. For example, uerr() is the macro used for error level messages from the USB subsystem and is enabled with CONFIG_DEBUG_USB_ERROR.
+
+ The base debug macro names, their priority, and configuration variable are summarized below: +
+
+ info(). The info() macro is the lowest priority (LOG_INFO) and is intended to provide general information about the flow of program execution so that you can get an overview of the behavior of the program. info() is often very chatty and voluminous and usually more information than you may want to see. The info() macro is controlled via CONFIG_DEBUG_subsystem_INFO
+
+ warn(). The warn() macro has medium priority (LOG_WARN) and is controlled by CONFIG_DEBUG_subsystem_WARN. The warn() is intended to
+ note exceptional or unexpected conditions that meigh be potential
+ errors or, perhaps, minor errors that easily recovered.
+
+ err(). This is a high priority debug macro (LOG_ERROR) and controlled by CONFIG_DEBUG_subsystem_ERROR. The err() is reserved to indicate important error conditions.
+
+ alert(). The highest priority debug macro (LOG_EMERG) and is controlled by CONFIG_DEBUG_ALERT. The alert() macro is reserved for use solely by assertion and crash handling logic. It also differs from the other macros in that there it cannot be enabled per subsystem.
+
+ In the NuttX SYSLOG implementation, the underlying device logic the supports the SYSLOG output is referred to as a SYSLOG channel. Each SYSLOG channel is represented by an interface defined in include/nuttx/syslog/syslog.h:
+
+ /* This structure provides the interface to a SYSLOG device */
+
+ typedef CODE int (*syslog_putc_t)(int ch);
+ typedef CODE int (*syslog_flush_t)(void);
+
+ struct syslog_channel_s
+ {
+ /* I/O redirection methods */
+
+ syslog_putc_t sc_putc; /* Normal buffered output */
+ syslog_putc_t sc_force; /* Low-level output for interrupt handlers */
+ syslog_flush_t sc_flush; /* Flush buffered output (on crash) */
+
+ /* Implementation specific logic may follow */
+ };
+
+
+ The channel interface is instantiated by calling syslog_channel():
+
syslog_channel()Function Prototype:
++int syslog_channel(FAR const struct syslog_channel_s *channel); ++
Description: + Configure the SYSLOG function to use the provided channel to generate SYSLOG output. +
+
+ syslog_channel() is a non-standard, internal OS interface and is not available to applications. It may be called numerous times as necessary to change channel interfaces.
+ By default, all system log output goes to console (/dev/console).
+
Input Parmeters: +
+ channel: Describes 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.
+
+ The initial, default SYSLOG channel is established with statically initialized global variables so that some level of SYSLOG output may be available immediately upon reset. This initialized data is in the file drivers/syslog/syslog_channel.c. The initial SYSLOG capability is determined by the selected SYSLOG channel:
+
+ In-Memory Buffer (RAMLOG). Full SYSLOG capability as available at reset. +
+ Serial Console. If the serial implementation provides the low-level character output function up_putc(), then that low level serial output is available as soon as the serial device has been configured.
+
+ For all other SYSLOG channels, all SYSLOG output goes to the bit- + bucket until the SYSLOG channel device has been initialized. +
+ The syslog channel device is initialized when the bring-up logic calls syslog_initialize():
+
syslog_initialize()Function Prototype:
++#ifndef CONFIG_ARCH_SYSLOG +int syslog_initialize(enum syslog_init_e phase); +#else +# define syslog_initialize(phase) +#endif ++
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 SYSLOG 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.
+
+ Different types of SYSLOG devices have different OS initialization
+ requirements. Some are available immediately at reset, some are available
+ after some basic OS initialization, and some only after OS is fully
+ initialized. In order to satisfy these different initialization
+ requirements, syslog_initialize() is called twice from the boot-up logic:
+
+ syslog_initialize() is called from the architecture-specific up_initialize() function as some as basic hardware resources have been initialized: Timers, interrupts, etc. In this case, syslog_initialize() is called with the argument SYSLOG_INIT_EARLY.
+
+ syslog_initialize() is called again from os_start() when the full OS initialization has completed, just before the application main entry point is spawned. In this case, syslog_initialize() is called with the argument SYSLOG_INIT_LATE.
+
+ There are other types of SYSLOG channel devices that may require even further initialization. For example, the file SYSLOG channel (described below) cannot be initialized until the necessary file systems have been mounted. +
+ ++ The typical SYSLOG device is the system console. If you are using a serial console, for example, then the SYSLOG output will appear on that serial port. +
+
+ This SYSLOG channel is automatically selected by syslog_initialize() in the LATE initialization phase based on configuration options. The configuration options that affect this channel selection include:
+
+ CONFIG_DEV_CONSOLE. This setting indicates that the system supports a console device, i.e., that the character device /dev/console exists.
+
+ CONFIG_SERIAL_CONSOLE. This configuration option is automatically selected when a UART or USART is configured as the system console. There is no user selection.
+
+ CONFIG_SYSLOG_CONSOLE. This configuration option is manually selected from the SYSLOG menu. This is the option that acutally enables the SYSLOG console device. It depends on CONFIG_DEV_CONSOLE and it will automatically select CONFIG_SYSLOG_SERIAL_CONSOLE if CONFIG_SERIAL_CONSOLE is selected.
+
+ CONFIG_ARCH_LOWPUTC. This is an indication from the architecture configuration that the platform supports the up_putc() interface. up_putc() is a very low level UART interface that can even be used from interrupt handling.
+
+ CONFIG_SYSLOG_SERIAL_CONSOLE. This enables certain features of the SYSLOG operation that depend on a serial console. If CONFIG_ARCH_LOWPUTC is also selected, for example, then up_putc() will be used for the forced SYSLOG output.
+
+ Interrupt level SYSLOG output will be lost unless: (1) the interrupt buffer
+ is enabled to support serialization, or (2) a serial console is used and
+ up_putc() is supported.
+
+ NOTE: The console channel uses the fixed character device at /dev/console. The console channel is not synonymous with stdout (or file descriptor 1). stdout is the current output from a task when, say, printf() if used. Initially, stdout does, indeed, use the /dev/console device. However, stdout may subsequently be redirected to some other device or file. This is always the case, for example, when a transient device is used for a console -- such as a USB console or a Telnet console. The SYSLOG channel is not redirected as stdout is; the SYSLOG channel will stayed fixed (unless it is explicitly changed via syslog_channel()).
+
+ References: drivers/syslog/syslog_consolechannel.c and
+ drivers/syslog/syslog_device.c
+
+ The system console device, /dev/console, is a character driver with some special properties. However, any character driver may be used as the SYSLOG output channel. For example, suppose you have a serial console on /dev/ttyS0 and you want SYSLOG output on /dev/ttyS1. Or suppose you support only a Telnet console but want to capture debug output /dev/ttyS0.
+
+ This SYSLOG device channel is selected with CONFIG_SYSLOG_CHAR and has no other dependencies. Differences fromthe SYSLOG console channel include:
+
+ CONFIG_SYSLOG_DEVPATH. This configuration option string must be set provide the full path to the character device to be used.
+
+ The forced SYSLOG output always goes to the bit-bucket. This means that interrupt level SYSLOG output will be lost unless the interrupt buffer is enabled to support serialization. +
+ CONFIG_SYSLOG_CHAR_CRLF. If CONFIG_SYSLOG_CHAR_CRLF is selected, then linefeeds in the SYSLOG output will be expanded to Carriage Return plus Linefeed. Since the character device is not a console device, the addition of carriage returns to line feeds would not be performed otherwise. You would probably want this expansion if you use a serial terminal program with the character device output.
+
+ References: drivers/syslog/syslog_devchannel.c and drivers/syslog/syslog_device.c
+
+ Files can also be used as the sink for SYSLOG output. There is, however, a very fundamental difference in using a file as opposed the system console, a RAM buffer, or character device: You must first mount the file system that supports the SYSLOG file. That difference means that the file SYSLOG channel cannot be supported during the boot-up phase but can be instantiated later when board level logic configures the application environment, including mounting of the file systems. +
+
+ The interface syslog_file_channel() is used to configure the SYSLOG file channel:
+
syslog_file_channel()Function Prototype:
++#ifdef CONFIG_SYSLOG_FILE +int syslog_file_channel(FAR const char *devpath); +#endif ++
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.
+
+ References: drivers/syslog/syslog_filechannel.c, drivers/syslog/syslog_device.c, and include/nuttx/syslog/syslog.h.
+
+ The RAMLOG is a standalone feature that can be used to buffer any + character data in memory. There are, however, special configurations + that can be used to configure the RAMLOG as a SYSLOG channel. The RAMLOG + functionality is described in a more general way in the following + paragraphs. +
+ ++ The RAM logging driver can also accept debug output data from interrupt handler with no special serialization buffering. As an added benefit, the RAM logging driver is much less invasive. Since no actual I/O is performed with the debug output is generated, the RAM logger tends to be much faster and will interfere much less when used with time critical drivers. +
++ The RAM logging driver is similar to a pipe in that it saves the debugging output in a circular buffer in RAM. It differs from a pipe in numerous details as needed to support logging. +
+
+ This driver is built when CONFIG_RAMLOG is defined in the Nuttx configuration.
+
dmesg
+ When the RAMLOG (with SYSLOG) is enabled, a new NuttShell (NSH) command will appear: dmesg. The dmesg command will dump the contents of the circular buffer to the console (and also clear the circular buffer).
+
+ CONFIG_RAMLOG: Enables the RAM logging feature
+
+ CONFIG_RAMLOG_CONSOLE: Use the RAM logging device as a system console. If this feature is enabled (along with CONFIG_DEV_CONSOLE), then all console output will be re-directed to a circular buffer in RAM. This might be useful, for example, if the only console is a Telnet console. Then in that case, console output from non-Telnet threads will go to the circular buffer and can be viewed using the NSH dmesg command. This optional is not useful in other scenarios.
+
+ CONFIG_RAMLOG_SYSLOG: Use the RAM logging device for the SYSLOG interface. If this feature is enabled, then all debug output will be re-directed to the circular buffer in RAM. This RAM log can be viewed from NSH using the dmesg command. NOTE: Unlike the limited, generic character driver SYSLOG device, the RAMLOG can be used to capture debug output from
+ interrupt level handlers.
+
+ CONFIG_RAMLOG_NPOLLWAITERS: The number of threads than can be waiting for this driver on poll(). Default: 4
+
+ If CONFIG_RAMLOG_CONSOLE or CONFIG_RAMLOG_SYSLOG is selected, then the following must also be provided:
+
+ CONFIG_RAMLOG_BUFSIZE: The size of the circular buffer to use. Default: 1024 bytes.
+
+ Other miscellaneous settings +
+
+ CONFIG_RAMLOG_CRLF: Pre-pend a carriage return before every linefeed that goes into the RAM log.
+
+ CONFIG_RAMLOG_NONBLOCKING: Reading from the RAMLOG will never block if the RAMLOG is empty. If the RAMLOG is empty, then zero is returned (usually interpreted as end-of-file). If you do not define this, the NSH dmesg command will lock up when called! So you probably do want this!
+
+ CONFIG_RAMLOG_NPOLLWAITERS: The maximum number of threads that may be waiting on the poll method.
+
Power Management (PM) Sub-System. NuttX supports a simple power management (PM) sub-system. This sub-system: @@ -5632,12 +6076,12 @@ int kbd_decode(FAR struct lib_instream_s *stream, FAR struct kbd_getstate_s *sta Multiple PM domains might be useful, for example, if you would want to control power states associated with a network separately from power states associated with a user interface.
-
All PM interfaces are declared in the file include/nuttx/power/pm.h.
pm_initialize()pm_initialize()Function Prototype:
#include <nuttx/power/pm.h> @@ -5654,7 +6098,7 @@ None None -6.4.2.2
+pm_register()6.5.2.2
pm_register()Function Prototype:
#include <nuttx/power/pm.h> @@ -5674,7 +6118,7 @@ int pm_register(FAR struct pm_callback_s *callbacks); Zero (OK) on success; otherwise a negatederrnovalue is returned. -6.4.2.3
+pm_activity()6.5.2.3
pm_activity()Function Prototype:
#include <nuttx/power/pm.h> @@ -5703,7 +6147,7 @@ void pm_activity(int domain, int priority); This function may be called from an interrupt handler (this is the ONLY PM function that may be called from an interrupt handler!). -6.4.2.4
+pm_checkstate()6.5.2.4
pm_checkstate()Function Prototype:
#include <nuttx/power/pm.h> @@ -5733,7 +6177,7 @@ enum pm_state_e pm_checkstate(int domain); The recommended power management state. -6.4.2.5
+pm_changestate()6.5.2.5
pm_changestate()Function Prototype:
#include <nuttx/power/pm.h>
@@ -5763,14 +6207,14 @@ enum pm_state_e pm_checkstate(int domain);
suspend the IDLE thread before it completes the entire state change unless interrupts are disabled throughout the state change.
-6.4.3 Callbacks
+6.5.3 Callbacks
The struct pm_callback_s includes the pointers to the driver callback functions.
This structure is defined include/nuttx/power/pm.h.
These callback functions can be used to provide power management information to the driver.
-6.4.3.1 prepare()
+6.5.3.1 prepare()
Function Prototype:
int (*prepare)(FAR struct pm_callback_s *cb, int domain, enum pm_state_e pmstate);
@@ -5800,7 +6244,7 @@ int (*prepare)(FAR struct pm_callback_s *cb, int domain, enum pm_state_e pmstate
consumption modes!
-6.4.3.1 notify()
+6.5.3.1 notify()
Function Prototype:
#include <nuttx/power/pm.h>
diff --git a/drivers/syslog/README.txt b/drivers/syslog/README.txt
index 9133dcaeed5..3d3da0bdc3e 100644
--- a/drivers/syslog/README.txt
+++ b/drivers/syslog/README.txt
@@ -149,6 +149,10 @@ SYSLOG Channels
Configure the SYSLOGging function to use the provided channel to
generate SYSLOG output.
+ syslog_channel() is a non-standard, internal OS interface and is not
+ available to applications. It may be called numerous times as
+ necessary to change channel interfaces.
+
Input Parmeters:
* channel - Provides the interface to the channel to be used.
@@ -158,21 +162,6 @@ SYSLOG Channels
Zero (OK)is returned on success. A negated errno value is returned
on any failure.
- syslog_channel() is a non-standard, internal OS interface and is not
- avaiable to applications. It may be called numerous times as necessary to
- change channel interfaces.
-
- By default, all system log output goes to console (/dev/console). But
- that behavior can be changed by the defining CONFIG_SYSLOG in the NuttX
- configuration. In that, case all low-level debug output will go through
- syslog_putc().
-
- NOTE: Using the NuttX configuration tool, you will need to enable basic
- SYSLOG features under the File System menu. Later we will talk about the
- RAMLOG device. That device is configured in the SYSLOG section under the
- Device Drivers menu. But you will only see the options there if you
- enable the basic SYSLOG capability in the File System menu first.
-
SYSLOG Channel Initialization
-----------------------------
The initial, default SYSLOG channel is established with statically
@@ -218,6 +207,7 @@ SYSLOG Channels
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:
@@ -302,7 +292,7 @@ SYSLOG Channel Options
support only a Telnet console but want to capture debug output
/dev/ttyS0.
- This SYSLOG device chhannl is selected with CONFIG_SYSLOG_CHAR and has no
+ This SYSLOG device channel is selected with CONFIG_SYSLOG_CHAR and has no
other dependencies. Differences fromthe SYSLOG console channel include:
* CONFIG_SYSLOG_DEVPATH. This configuration option string must be set
@@ -330,7 +320,7 @@ SYSLOG Channel Options
can be instantiated later when board level logic configures the application
environment, including mounting of the file systems.
- The interface syslog_file_channal() is used to configure the SYSLOG file
+ The interface syslog_file_channel() is used to configure the SYSLOG file
channel:
syslog_file_channel()
@@ -363,6 +353,7 @@ SYSLOG Channel Options
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
@@ -370,6 +361,7 @@ SYSLOG Channel Options
file.
Returned Value:
+
Zero (OK) is returned on success; a negated errno value is returned on
any failure.
@@ -424,12 +416,11 @@ RAM Logging Device
threads will go to the circular buffer and can be viewed using the NSH
dmesg command. This optional is not useful in other scenarios.
* CONFIG_RAMLOG_SYSLOG - Use the RAM logging device for the syslogging
- interface. If this feature is enabled (along with CONFIG_SYSLOG),
- then all debug output (only) will be re-directed to the circular
- buffer in RAM. This RAM log can be viewed from NSH using the 'dmesg'
- command. NOTE: Unlike the limited, generic character driver SYSLOG
- device, the RAMLOG *can* be used to capture debug output from
- interrupt level handlers.
+ interface. If this feature is enabled, then all debug output (only)
+ will be re-directed to the circular buffer in RAM. This RAM log can
+ be viewed from NSH using the 'dmesg' command. NOTE: Unlike the
+ limited, generic character driver SYSLOG device, the RAMLOG *can* be
+ used to capture debug output from interrupt level handlers.
* CONFIG_RAMLOG_NPOLLWAITERS - The number of threads than can be waiting
for this driver on poll(). Default: 4