lib/vsprintf: add %*pE[achnops] format specifier
This allows user to print a given buffer as an escaped string. The
rules are applied according to an optional mix of flags provided by
additional format letters.
For example, if the given buffer is:
1b 62 20 5c 43 07 22 90 0d 5d
The result strings would be:
%*pE "\eb \C\a"\220\r]"
%*pEhp "\x1bb \C\x07"\x90\x0d]"
%*pEa "\e\142\040\\\103\a\042\220\r\135"
Please, read Documentation/printk-formats.txt and lib/string_helpers.c
kernel documentation to get further information.
[akpm@linux-foundation.org: tidy up comment layout, per Joe]
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Suggested-by: Joe Perches <joe@perches.com>
Cc: "John W . Linville" <linville@tuxdriver.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt
index b449821..5a615c1 100644
--- a/Documentation/printk-formats.txt
+++ b/Documentation/printk-formats.txt
@@ -70,6 +70,38 @@
For printing a dma_addr_t type which can vary based on build options,
regardless of the width of the CPU data path. Passed by reference.
+Raw buffer as an escaped string:
+
+ %*pE[achnops]
+
+ For printing raw buffer as an escaped string. For the following buffer
+
+ 1b 62 20 5c 43 07 22 90 0d 5d
+
+ few examples show how the conversion would be done (the result string
+ without surrounding quotes):
+
+ %*pE "\eb \C\a"\220\r]"
+ %*pEhp "\x1bb \C\x07"\x90\x0d]"
+ %*pEa "\e\142\040\\\103\a\042\220\r\135"
+
+ The conversion rules are applied according to an optional combination
+ of flags (see string_escape_mem() kernel documentation for the
+ details):
+ a - ESCAPE_ANY
+ c - ESCAPE_SPECIAL
+ h - ESCAPE_HEX
+ n - ESCAPE_NULL
+ o - ESCAPE_OCTAL
+ p - ESCAPE_NP
+ s - ESCAPE_SPACE
+ By default ESCAPE_ANY_NP is used.
+
+ ESCAPE_ANY_NP is the sane choice for many cases, in particularly for
+ printing SSIDs.
+
+ If field width is omitted the 1 byte only will be escaped.
+
Raw buffer as a hex string:
%*ph 00 01 02 ... 3f
%*phC 00:01:02: ... :3f