Logging

Levels

Use the level-named macros as their names suggest: PBL_LOG_ERR() and PBL_LOG_WRN() for errors and warnings, PBL_LOG_DBG() for routine lifecycle and state-transition messages, and PBL_LOG_INFO() only for events that deserve attention in a default-level capture. A code path that can fire repeatedly in normal use must not log at INFO.

Modules

A source file can belong to a log module with its own Kconfig level. Declare the level with the Kconfig template:

module = TASK_WDT
module-str = Task watchdog
source "subsys/logging/Kconfig.template.log_level"

and bind the file to it:

#include <pbl/logging/logging.h>

PBL_LOG_MODULE_DEFINE(task_wdt, CONFIG_TASK_WDT_LOG_LEVEL);

PBL_LOG_DBG("channel %d armed", id);

Messages above the module level are compiled out. Files without a module use the default level.

Hashing

With CONFIG_LOG_HASHED, the default, format strings are replaced by tokens at build time: the binary only carries a hash and the arguments, and the console dehashes them with the dictionary the build writes (see pbl console). A hashed message takes at most 7 conversions, 2 of them %s, 32-bit arguments and no %%; do not mix %s with %x or %X in one message.

Configuration

CONFIG_DEFAULT_LOG_LEVEL_<LEVEL>:

Default log level, where <LEVEL> is one of ERROR, WARNING, INFO (default), DEBUG or DEBUG_VERBOSE.

CONFIG_LOG_HASHED=n:

Disable log message hashing. This increases ROM usage, but logs no longer need a dictionary to decode.

CONFIG_<MODULE>_LOG_LEVEL_RUNTIME=y:

Keep all log messages of a module in the image and filter them at runtime, using CONFIG_<MODULE>_LOG_LEVEL as the initial level. The level is changed with PBL_LOG_MODULE_LEVEL_SET(name, level) and read with PBL_LOG_MODULE_LEVEL_GET(name), where name is the one given to PBL_LOG_MODULE_DEFINE. Messages accepted by the module level skip the serial and flash log level filters. This increases ROM usage for that module.

The Settings → System → Debugging → Vibe Log Info preference sets the alert UI, vibe score and vibe pattern modules to DEBUG, so their traces reach bug reports. Normal firmware enables runtime levels for these modules by default. Disabling the preference restores each module’s configured level; the preference is also applied at boot. Recovery firmware keeps compile-time logging by default.