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-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.