Merge branch 'doc/review_system_log-index' into 'master'

Review log.rst and index.rst files in api-reference/system

See merge request idf/esp-idf!4738

components/log/README.rst

@@ -4,26 +4,34 @@ Logging library
 Overview
 --------
 
-Log library has two ways of managing log verbosity: compile time, set via menuconfig; and runtime, using :cpp:func:`esp_log_level_set` function.
+The logging library provides two ways for setting log verbosity:
 
-The log levels are Error, Warning, Info, Debug, and Verbose (from lowest to highest level of verbosity).
+- **At compile time**: in menuconfig, set the verbosity level using the option :envvar:`CONFIG_LOG_DEFAULT_LEVEL`. All logging statements for verbosity levels higher than :envvar:`CONFIG_LOG_DEFAULT_LEVEL` will be removed by the preprocessor.
+- **At runtime**: all logs for verbosity levels lower than :envvar:`CONFIG_LOG_DEFAULT_LEVEL` are enabled by default. The function :cpp:func:`esp_log_level_set` can be used to set a logging level on a per module basis. Modules are identified by their tags, which are human-readable ASCII zero-terminated strings.
 
-At compile time, filtering is done using :envvar:`CONFIG_LOG_DEFAULT_LEVEL` option, set via menuconfig. All logging statements for levels higher than :envvar:`CONFIG_LOG_DEFAULT_LEVEL` will be removed by the preprocessor.
+There are the following verbosity levels:
 
-At run time, all logs below :envvar:`CONFIG_LOG_DEFAULT_LEVEL` are enabled by default. :cpp:func:`esp_log_level_set` function may be used to reduce logging level per module. Modules are identified by their tags, which are human-readable ASCII zero-terminated strings. 
+- Error (lowest)
+- Warning
+- Info
+- Debug
+- Verbose (highest)
+
+.. note::
+
+    The function :cpp:func:`esp_log_level_set` cannot set logging levels higher than specified by :envvar:`CONFIG_LOG_DEFAULT_LEVEL`. To increase log level for a specific file at compile time, use the macro `LOG_LOCAL_LEVEL` (see the details below).
 
-Note that :cpp:func:`esp_log_level_set` can not increase logging level beyound that set by :envvar:`CONFIG_LOG_DEFAULT_LEVEL`. To increase log level for a specific file at compile time, `LOG_LOCAL_LEVEL` macro can be used (see below for details).
 
 How to use this library
 -----------------------
 
-In each C file which uses logging functionality, define TAG variable like this:
+In each C file that uses logging functionality, define the TAG variable as shown below:
 
 .. code-block:: c
 
    static const char* TAG = "MyModule";
 
-then use one of logging macros to produce output, e.g:
+Then use one of logging macros to produce output, e.g:
 
 .. code-block:: c
 
@@ -37,23 +45,24 @@ Several macros are available for different verbosity levels:
 * ``ESP_LOGD`` - debug
 * ``ESP_LOGV`` - verbose (highest)
 
-Additionally there is an ``_EARLY`` variant for each of these macros (e.g. :c:macro:`ESP_EARLY_LOGE`). These variants can run in startup code, before heap allocator and syscalls have been initialized. When compiling bootloader, normal ``ESP_LOGx`` macros fall back to the same implementation as ``ESP_EARLY_LOGx`` macros. So the only place where ``ESP_EARLY_LOGx`` have to be used explicitly is the early startup code, such as heap allocator initialization code.
+Additionally, there are ``ESP_EARLY_LOGx`` versions for each of these macros, e.g., :c:macro:`ESP_EARLY_LOGE`. These versions have to be used explicitly in the early startup code only, before heap allocator and syscalls have been initialized. Normal ``ESP_LOGx`` macros can also be used while compiling the bootloader, but they will fall back to the same implementation as ``ESP_EARLY_LOGx`` macros.
 
-To override default verbosity level at file or component scope, define ``LOG_LOCAL_LEVEL`` macro. At file scope, define it before including ``esp_log.h``, e.g.:
+To override default verbosity level at file or component scope, define the ``LOG_LOCAL_LEVEL`` macro.
+
+At file scope, define it before including ``esp_log.h``, e.g.:
 
 .. code-block:: c
 
    #define LOG_LOCAL_LEVEL ESP_LOG_VERBOSE
    #include "esp_log.h"
 
-
-At component scope, define it in component makefile:
+At component scope, define it in the component makefile:
 
 .. code-block:: make
 
    CFLAGS += -D LOG_LOCAL_LEVEL=ESP_LOG_DEBUG
 
-To configure logging output per module at runtime, add calls to :cpp:func:`esp_log_level_set` function:
+To configure logging output per module at runtime, add calls to the function :cpp:func:`esp_log_level_set` as follows:
 
 .. code-block:: c
 
@@ -64,5 +73,5 @@ To configure logging output per module at runtime, add calls to :cpp:func:`esp_l
 Logging to Host via JTAG
 ^^^^^^^^^^^^^^^^^^^^^^^^
 
-By default logging library uses vprintf-like function to write formatted output to dedicated UART. By calling a simple API, all log output may be routed to JTAG instead, making logging several times faster. For details please refer to section :ref:`app_trace-logging-to-host`.
+By default, the logging library uses the vprintf-like function to write formatted output to the dedicated UART. By calling a simple API, all log output may be routed to JTAG instead, making logging several times faster. For details, please refer to Section :ref:`app_trace-logging-to-host`.
 

docs/en/api-reference/system/index.rst

@@ -26,4 +26,4 @@ System API
    Miscellaneous System APIs <system>
 
 
-Example code for this API section is provided in :example:`system` directory of ESP-IDF examples.
+Code examples for this API section are provided in the :example:`system` directory of ESP-IDF examples.

docs/en/api-reference/system/log.rst

@@ -3,11 +3,11 @@
 Application Example
 -------------------
 
-Log library is commonly used by most of esp-idf components and examples. For demonstration of log functionality check :idf:`examples` folder of `espressif/esp-idf <https://github.com/espressif/esp-idf>`_ repository, that among others, contains the following examples:
+The logging library is commonly used by most esp-idf components and examples. For demonstration of log functionality, check ESP-IDF's :idf:`examples` directory. The most revelant examples that deal with logging are the following:
  
-* :example:`system/ota` 
-* :example:`storage/sd_card` 
-* :example:`protocols/https_request` 
+* :example:`system/ota`
+* :example:`storage/sd_card`
+* :example:`protocols/https_request`
 
 API Reference
 -------------