From 1ecb6beb95fcf3369bcd964f25d8954d048846a7 Mon Sep 17 00:00:00 2001 From: Heinrich Schuchardt Date: Mon, 14 Sep 2020 10:12:19 +0200 Subject: [PATCH] doc: remove redundant doc/README.log doc/README.log was already moved to doc/develop/logging.rst but has been recreated by an incorrect merge. Signed-off-by: Heinrich Schuchardt Reviewed-by: Simon Glass --- doc/README.log | 283 ------------------------------------------------- 1 file changed, 283 deletions(-) delete mode 100644 doc/README.log diff --git a/doc/README.log b/doc/README.log deleted file mode 100644 index a313399fc9..0000000000 --- a/doc/README.log +++ /dev/null @@ -1,283 +0,0 @@ -Logging in U-Boot -================= - -Introduction ------------- - -U-Boot's internal operation involves many different steps and actions. From -setting up the board to displaying a start-up screen to loading an Operating -System, there are many component parts each with many actions. - -Most of the time this internal detail is not useful. Displaying it on the -console would delay booting (U-Boot's primary purpose) and confuse users. - -But for digging into what is happening in a particular area, or for debugging -a problem it is often useful to see what U-Boot is doing in more detail than -is visible from the basic console output. - -U-Boot's logging feature aims to satisfy this goal for both users and -developers. - - -Logging levels --------------- - -There are a number logging levels available, in increasing order of verbosity: - - LOGL_EMERG - Printed before U-Boot halts - LOGL_ALERT - Indicates action must be taken immediate or U-Boot will crash - LOGL_CRIT - Indicates a critical error that will cause boot failure - LOGL_ERR - Indicates an error that may cause boot failure - LOGL_WARNING - Warning about an unexpected condition - LOGL_NOTE - Important information about progress - LOGL_INFO - Information about normal boot progress - LOGL_DEBUG - Debug information (useful for debugging a driver or subsystem) - LOGL_DEBUG_CONTENT - Debug message showing full message content - LOGL_DEBUG_IO - Debug message showing hardware I/O access - - -Logging category ----------------- - -Logging can come from a wide variety of places within U-Boot. Each log message -has a category which is intended to allow messages to be filtered according to -their source. - -The following main categories are defined: - - LOGC_NONE - Unknown category (e.g. a debug() statement) - UCLASS_... - Related to a particular uclass (e.g. UCLASS_USB) - LOGC_ARCH - Related to architecture-specific code - LOGC_BOARD - Related to board-specific code - LOGC_CORE - Related to core driver-model support - LOGC_DT - Related to device tree control - LOGC_EFI - Related to EFI implementation - - -Enabling logging ----------------- - -The following options are used to enable logging at compile time: - - CONFIG_LOG - Enables the logging system - CONFIG_LOG_MAX_LEVEL - Max log level to build (anything higher is compiled - out) - CONFIG_LOG_CONSOLE - Enable writing log records to the console - -If CONFIG_LOG is not set, then no logging will be available. - -The above have SPL and TPL versions also, e.g. CONFIG_SPL_LOG_MAX_LEVEL and -CONFIG_TPL_LOG_MAX_LEVEL. - - -Temporary logging within a single file --------------------------------------- - -Sometimes it is useful to turn on logging just in one file. You can use this: - - #define LOG_DEBUG - -to enable building in of all logging statements in a single file. Put it at -the top of the file, before any #includes. This overrides any log-level setting -in U-Boot, including CONFIG_LOG_DEFAULT_LEVEL, but just for that file. - - -Convenience functions ---------------------- - -A number of convenience functions are available to shorten the code needed -for logging: - - log_err(_fmt...) - log_warning(_fmt...) - log_notice(_fmt...) - log_info(_fmt...) - log_debug(_fmt...) - log_content(_fmt...) - log_io(_fmt...) - -With these the log level is implicit in the name. The category is set by -LOG_CATEGORY, which you can only define once per file, above all #includes: - - #define LOG_CATEGORY LOGC_ALLOC - -or - - #define LOG_CATEGORY UCLASS_SPI - -Remember that all uclasses IDs are log categories too. - - -Log commands ------------- - -The 'log' command provides access to several features: - - level - access the default log level - format - access the console log format - rec - output a log record - test - run tests - -Type 'help log' for details. - - -Using DEBUG ------------ - -U-Boot has traditionally used a #define called DEBUG to enable debugging on a -file-by-file basis. The debug() macro compiles to a printf() statement if -DEBUG is enabled, and an empty statement if not. - -With logging enabled, debug() statements are interpreted as logging output -with a level of LOGL_DEBUG and a category of LOGC_NONE. - -The logging facilities are intended to replace DEBUG, but if DEBUG is defined -at the top of a file, then it takes precedence. This means that debug() -statements will result in output to the console and this output will not be -logged. - - -Logging destinations --------------------- - -If logging information goes nowhere then it serves no purpose. U-Boot provides -several possible determinations for logging information, all of which can be -enabled or disabled independently: - - console - goes to stdout - syslog - broadcast RFC 3164 messages to syslog servers on UDP port 514 - -The syslog driver sends the value of environmental variable 'log_hostname' as -HOSTNAME if available. - -Log format ----------- - -You can control the log format using the 'log format' command. The basic -format is: - - LEVEL.category,file.c:123-func() message - -In the above, file.c:123 is the filename where the log record was generated and -func() is the function name. By default ('log format default') only the -function name and message are displayed on the console. You can control which -fields are present, but not the field order. - - -Filters -------- - -Filters are attached to log drivers to control what those drivers emit. Only -records that pass through the filter make it to the driver. - -Filters can be based on several criteria: - - - maximum log level - - in a set of categories - - in a set of files - -If no filters are attached to a driver then a default filter is used, which -limits output to records with a level less than CONFIG_LOG_MAX_LEVEL. - - -Logging statements ------------------- - -The main logging function is: - - log(category, level, format_string, ...) - -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. - -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: - - return log_ret(uclass_first_device(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. - - -Code size ---------- - -Code size impact depends largely on what is enabled. The following numbers are -generated by 'buildman -S' for snow, which is a Thumb-2 board (all units in -bytes): - -This series: adds bss +20.0 data +4.0 rodata +4.0 text +44.0 -CONFIG_LOG: bss -52.0 data +92.0 rodata -635.0 text +1048.0 -CONFIG_LOG_MAX_LEVEL=7: bss +188.0 data +4.0 rodata +49183.0 text +98124.0 - -The last option turns every debug() statement into a logging call, which -bloats the code hugely. The advantage is that it is then possible to enable -all logging within U-Boot. - - -To Do ------ - -There are lots of useful additions that could be made. None of the below is -implemented! If you do one, please add a test in test/py/tests/test_log.py - -Convenience functions to support setting the category: - - log_arch(level, format_string, ...) - category LOGC_ARCH - log_board(level, format_string, ...) - category LOGC_BOARD - log_core(level, format_string, ...) - category LOGC_CORE - log_dt(level, format_string, ...) - category LOGC_DT - -More logging destinations: - - device - goes to a device (e.g. serial) - buffer - recorded in a memory buffer - -Convert debug() statements in the code to log() statements - -Support making printf() emit log statements a L_INFO level - -Convert error() statements in the code to log() statements - -Figure out what to do with BUG(), BUG_ON() and warn_non_spl() - -Figure out what to do with assert() - -Add a way to browse log records - -Add a way to record log records for browsing using an external tool - -Add commands to add and remove filters - -Add commands to add and remove log devices - -Allow sharing of printf format strings in log records to reduce storage size -for large numbers of log records - -Add a command-line option to sandbox to set the default logging level - -Convert core driver model code to use logging - -Convert uclasses to use logging with the correct category - -Consider making log() calls emit an automatic newline, perhaps with a logn() - function to avoid that - -Passing log records through to linux (e.g. via device tree /chosen) - -Provide a command to access the number of log records generated, and the -number dropped due to them being generated before the log system was ready. - -Add a printf() format string pragma so that log statements are checked properly - -Enhance the log console driver to show level / category / file / line -information - -Add a command to add new log records and delete existing records. - -Provide additional log() functions - e.g. logc() to specify the category - --- -Simon Glass -15-Sep-17 -- 2.39.5