X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=Documentation%2Fprintk-formats.txt;h=b784c270105f40e8320cd388cb9a8ef1e2d463f4;hb=d7ec9a05d6defda8432da574a2a888eed6fc29f6;hp=9b8d7f746b1a6ad3cdfaf2d2c93675ab69f4f12c;hpb=317dc34ab786d4f22bf7ed8ab546b9ae57f900d0;p=firefly-linux-kernel-4.4.55.git

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.