dynamic_debug: dynamic hex dump

Introduce print_hex_dump_debug() that can be dynamically controlled, similar to
pr_debug.

Also, make print_hex_dump_bytes() dynamically controlled

Implement only 'p' flag (_DPRINTK_FLAGS_PRINT) to keep it simple since hex dump prints
multiple lines and long prefix would impact readability.
To provide line/file etc. information, use pr_debug or similar
before/after print_hex_dump_debug()

Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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).