u-boot/doc/README.log

1 Logging in U-Boot
5 ------------
7 U-Boot's internal operation involves many different steps and actions. From
8 setting up the board to displaying a start-up screen to loading an Operating
12 console would delay booting (U-Boot's primary purpose) and confuse users.
15 a problem it is often useful to see what U-Boot is doing in more detail than
18 U-Boot's logging feature aims to satisfy this goal for both users and
23 --------------
27    LOGL_EMERG	- Printed before U-Boot halts
28    LOGL_ALERT	- Indicates action must be taken immediate or U-Boot will crash
29    LOGL_CRIT	- Indicates a critical error that will cause boot failure
30    LOGL_ERR	- Indicates an error that may cause boot failure
31    LOGL_WARNING	- Warning about an unexpected condition
32    LOGL_NOTE	- Important information about progress
33    LOGL_INFO	- Information about normal boot progress
34    LOGL_DEBUG	- Debug information (useful for debugging a driver or subsystem)
35    LOGL_DEBUG_CONTENT	- Debug message showing full message content
36    LOGL_DEBUG_IO	- Debug message showing hardware I/O access
40 ----------------
42 Logging can come from a wide variety of places within U-Boot. Each log message
48    LOGC_NONE	- Unknown category (e.g. a debug() statement)
49    UCLASS_...	- Related to a particular uclass (e.g. UCLASS_USB)
50    LOGC_ARCH	- Related to architecture-specific code
51    LOGC_BOARD	- Related to board-specific code
52    LOGC_CORE	- Related to core driver-model support
53    LOGC_DT	- Related to device tree control
54    LOGC_EFI	- Related to EFI implementation
58 ----------------
62    CONFIG_LOG		- Enables the logging system
63    CONFIG_MAX_LOG_LEVEL - Max log level to build (anything higher is compiled
65    CONFIG_LOG_CONSOLE	- Enable writing log records to the console
73 --------------------------------------
82 To actually get U-Boot to output this you need to also set the default logging
83 level - e.g. set CONFIG_LOG_DEFAULT_LEVEL to 7 (LOGL_DEBUG) or more. Otherwise
88 ---------------------
114 ------------
118    level - access the default log level
119    format - access the console log format
120    rec - output a log record
121    test - run tests
127 -----------
129 U-Boot has traditionally used a #define called DEBUG to enable debugging on a
130 file-by-file basis. The debug() macro compiles to a printf() statement if
143 --------------------
145 If logging information goes nowhere then it serves no purpose. U-Boot provides
149    console - goes to stdout
153 ----------
158    LEVEL.category,file.c:123-func() message
167 -------
174    - maximum log level
175    - in a set of categories
176    - in a set of files
183 ------------------
189 Also debug() and error() will generate log records  - these use LOG_CATEGORY
203 ---------
206 generated by 'buildman -S' for snow, which is a Thumb-2 board (all units in
210 CONFIG_LOG: bss -52.0 data +92.0 rodata -635.0 text +1048.0
215 all logging within U-Boot.
219 -----
226    log_arch(level, format_string, ...) - category LOGC_ARCH
227    log_board(level, format_string, ...) - category LOGC_BOARD
228    log_core(level, format_string, ...) - category LOGC_CORE
229    log_dt(level, format_string, ...) - category LOGC_DT
233    device - goes to a device (e.g. serial)
234    buffer - recorded in a memory buffer
257 Add a command-line option to sandbox to set the default logging level
278 Provide additional log() functions - e.g. logc() to specify the category
280 --
282 15-Sep-17