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authorRasmus Villemoes <linux@rasmusvillemoes.dk>2015-11-06 16:30:35 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2015-11-06 17:50:42 -0800
commitd7ec9a05d6defda8432da574a2a888eed6fc29f6 (patch)
tree453b5229f8165523c17dd4bd0baa04a281ced611 /Documentation/printk-formats.txt
parent317dc34ab786d4f22bf7ed8ab546b9ae57f900d0 (diff)
lib/vsprintf.c: update documentation
%n is no longer just ignored; it results in early return from vsnprintf. Also add a request to add test cases for future %p extensions. Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Reviewed-by: Martin Kletzander <mkletzan@redhat.com> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/printk-formats.txt')
-rw-r--r--Documentation/printk-formats.txt12
1 files changed, 6 insertions, 6 deletions
diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt
index 9b8d7f746b1a..b784c270105f 100644
--- a/Documentation/printk-formats.txt
+++ b/Documentation/printk-formats.txt
@@ -23,6 +23,10 @@ Example:
Reminder: sizeof() result is of type size_t.
+The kernel's printf does not support %n. For obvious reasons, floating
+point formats (%e, %f, %g, %a) are also not recognized. Use of any
+unsupported specifier or length qualifier results in a WARN and early
+return from vsnprintf.
Raw pointer value SHOULD be printed with %p. The kernel supports
the following extended format specifiers for pointer types:
@@ -305,13 +309,9 @@ Command from struct task_struct
Passed by reference.
-Ignored argument:
+If you add other %p extensions, please extend lib/test_printf.c with
+one or more test cases, if at all feasible.
- %n %n
-
- The argument passed will be ignored. In other words, literal "%n" will
- be in the output and the argument will be considered for next format
- specifier.
Thank you for your cooperation and attention.