[PATCH v2] log: force DEBUG when LOG_DEBUG is activated

Patrick Delaunay patrick.delaunay at foss.st.com
Tue Jul 12 09:39:49 CEST 2022

When CONFIG_LOG is activated, if LOG_DEBUG is defined in a file and
DEBUG is not defined the trace with debug() macro are not displayed,
because the parameter cond : _DEBUG = 0 is checked in debug_cond().

With this patch the define DEBUG, used to force the trace generated by
debug() macro, is linked with the define LOG_DEBUG, used to force the
trace generated by other macros (log_debug, dev_dbg, pr_debug).

We only need to define LOG_DEBUG in a file to activate all the
traces generated by any U-Boot debug macro, as it is described in

Signed-off-by: Patrick Delaunay <patrick.delaunay at foss.st.com>

Changes in v2:
- update logging.rst

 doc/develop/logging.rst | 19 +++++++------------
 include/log.h           |  3 +++
 2 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/doc/develop/logging.rst b/doc/develop/logging.rst
index 51095b05ba9..704a6bf1d84 100644
--- a/doc/develop/logging.rst
+++ b/doc/develop/logging.rst
@@ -66,26 +66,21 @@ 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.
-To actually get U-Boot to output this you need to also set the default logging
-level - e.g. set CONFIG_LOG_DEFAULT_LEVEL to 7 (:c:data:`LOGL_DEBUG`) or more.
-Otherwise debug output is suppressed and will not be generated.
+the top of the file, before any #includes and any message in the file will be
+written, regardless of the value of CONFIG_LOG_DEFAULT_LEVEL.
 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.
+file-by-file basis but LOG_DEBUG are intended to replace it with the logging
+facilities; DEBUG is activated when LOG_DEBUG is activated.
 With logging enabled, debug() statements are interpreted as logging output
-with a level of LOGL_DEBUG and a category of LOGC_NONE.
+with a level of LOGL_DEBUG and a category of LOG_CATEGORY.
-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
+With logging disabled, the debug() macro compiles to a printf() statement
+if DEBUG is enabled and to an empty statement if not.
 Logging statements
diff --git a/include/log.h b/include/log.h
index 8f35c10abb5..7abc70e4398 100644
--- a/include/log.h
+++ b/include/log.h
@@ -194,6 +194,9 @@ int _log_buffer(enum log_category_t cat, enum log_level_t level,
 #ifdef LOG_DEBUG
+#ifndef DEBUG
+#define DEBUG
 #define _LOG_DEBUG	0

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