This section lists the methods that can be used to aid in CHRE framework debugging.
The CHRE framework invokes the LOGx() macros defined in platform/include/chre/platform/log.h to log information into the system, for printf-style debugging. This capability is also exposed to nanoapps via chreLog(). Although it may not be strictly required, it is strongly recommended that the platform implementation directs these log messages to Android’s logcat system under the “CHRE” tag, where they will be automatically collected in bug reports. These logs must not wake the applications processor (AP), so they should be buffered on a best-effort basis and flushed to the AP opportunistically when it wakes up.
CHRE framework currently supports four levels, namely Error LOGE(), Warning LOGW(), Info LOGI() and Debug LOGD(). These correspond to the equivalent logcat levels. Choosing an appropriate level for logs, and logging only the necessary information to identify and debug failures can help avoid issues with “log spam”, such as log output that is difficult to read, or uninteresting “spammy” logs causing useful log messages to be pushed out of limited buffering space.
The CHRE framework currently only supports compile-time log level filtering. While it’s recommended to leave it at the default setting, the CHRE_MINIMUM_LOG_LEVEL build flag can be defined to one of the values set in util/include/chre/util/log_common.h to control which log levels are included in the binary.
A debug dump is human-readable text produced on-demand for debugging purposes. While LOGx() is useful for logging events as they happen, the debug dump is a complementary function typically used to output a snapshot of the framework's state, history, vital statistics, etc. The debug dump is especially useful for information that would be too spammy to log on every change, but is useful to diagnose potential issues. The CHRE framework produces a debug dump when requested via the Context Hub HAL’s built-in debug() method, which is automatically collected as part of the bug report process, and can be manually triggered via ADB using the following command:
adb root && adb shell lshal debug android.hardware.contexthub@1.0::IContexthub/default
DebugDumpManager is the framework module responsible for collecting debug dumps from the CHRE framework and nanoapps. Refer to the associated documentation in the source code for details on this process.
CHRE_ASSERT() and CHRE_ASSERT_LOG() can be used to help catch programmatic errors during development. However, since their use may have memory impact, they can be disabled by setting CHRE_ASSERTIONS_ENABLED to false in the Makefile. In general, assertions should be used sparingly - they are best applied to situations that would lead to potentially unrecoverable logical errors that are not handled by the code. For comparison, asserting that a pointer is not null is generally an anti-pattern (though the current CHRE codebase is not free of this), as dereferencing null would produce a crash anyways which should have equivalent debuggability as an assertion, among other reasons.