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-rw-r--r--Documentation/dynamic-debug-howto.txt15
1 files changed, 13 insertions, 2 deletions
diff --git a/Documentation/dynamic-debug-howto.txt b/Documentation/dynamic-debug-howto.txt
index 6e1684981da2..72322c6d7352 100644
--- a/Documentation/dynamic-debug-howto.txt
+++ b/Documentation/dynamic-debug-howto.txt
@@ -6,8 +6,16 @@ This document describes how to use the dynamic debug (dyndbg) feature.
Dynamic debug is designed to allow you to dynamically enable/disable
kernel code to obtain additional kernel information. Currently, if
-CONFIG_DYNAMIC_DEBUG is set, then all pr_debug()/dev_dbg() calls can
-be dynamically enabled per-callsite.
+CONFIG_DYNAMIC_DEBUG is set, then all pr_debug()/dev_dbg() and
+print_hex_dump_debug()/print_hex_dump_bytes() calls can be dynamically
+enabled per-callsite.
+
+If CONFIG_DYNAMIC_DEBUG is not set, print_hex_dump_debug() is just
+shortcut for print_hex_dump(KERN_DEBUG).
+
+For print_hex_dump_debug()/print_hex_dump_bytes(), format string is
+its 'prefix_str' argument, if it is constant string; or "hexdump"
+in case 'prefix_str' is build dynamically.
Dynamic debug has even more useful features:
@@ -202,6 +210,9 @@ The flags are:
t Include thread ID in messages not generated from interrupt context
_ No flags are set. (Or'd with others on input)
+For print_hex_dump_debug() and print_hex_dump_bytes(), only 'p' flag
+have meaning, other flags ignored.
+
For display, the flags are preceded by '='
(mnemonic: what the flags are currently equal to).