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Diffstat (limited to 'doc/develop/logging.rst')
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1 files changed, 30 insertions, 1 deletions
diff --git a/doc/develop/logging.rst b/doc/develop/logging.rst index 60c18c5b3a..f4e925048e 100644 --- a/doc/develop/logging.rst +++ b/doc/develop/logging.rst @@ -96,16 +96,45 @@ Also debug() and error() will generate log records - these use LOG_CATEGORY as the category, so you should #define this right at the top of the source file to ensure the category is correct. +Generally each log format_string ends with a newline. If it does not, then the +next log statement will have the LOGRECF_CONT flag set. This can be used to +continue the statement on the same line as the previous one without emitting +new header information (such as category/level). This behaviour is implemented +with log_console. Here is an example that prints a list all on one line with +the tags at the start: + +.. code-block:: c + + log_debug("Here is a list:"); + for (i = 0; i < count; i++) + log_debug(" item %d", i); + log_debug("\n"); + +Also see the special category LOGL_CONT and level LOGC_CONT. + You can also define CONFIG_LOG_ERROR_RETURN to enable the log_ret() macro. This can be used whenever your function returns an error value: .. code-block:: c - return log_ret(uclass_first_device(UCLASS_MMC, &dev)); + return log_ret(uclass_first_device_err(UCLASS_MMC, &dev)); This will write a log record when an error code is detected (a value < 0). This can make it easier to trace errors that are generated deep in the call stack. +The log_msg_ret() variant will print a short string if CONFIG_LOG_ERROR_RETURN +is enabled. So long as the string is unique within the function you can normally +determine exactly which call failed: + +.. code-block:: c + + ret = gpio_request_by_name(dev, "cd-gpios", 0, &desc, GPIOD_IS_IN); + if (ret) + return log_msg_ret("gpio", ret); + +Some functions return 0 for success and any other value is an error. For these, +log_retz() and log_msg_retz() are available. + Convenience functions ~~~~~~~~~~~~~~~~~~~~~ |