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-rw-r--r--Documentation/printk-formats.txt29
1 files changed, 29 insertions, 0 deletions
diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt
index 2216eb187c21..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:
@@ -119,6 +123,7 @@ Raw buffer as an escaped string:
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
%*phD 00-01-02- ... -3f
@@ -234,6 +239,7 @@ UUID/GUID addresses:
Passed by reference.
dentry names:
+
%pd{,2,3,4}
%pD{,2,3,4}
@@ -256,6 +262,8 @@ struct va_format:
va_list *va;
};
+ Implements a "recursive vsnprintf".
+
Do not use this feature without some mechanism to verify the
correctness of the format string and va_list arguments.
@@ -284,6 +292,27 @@ bitmap and its derivatives such as cpumask and nodemask:
Passed by reference.
+Network device features:
+
+ %pNF 0x000000000000c000
+
+ For printing netdev_features_t.
+
+ Passed by reference.
+
+Command from struct task_struct
+
+ %pT ls
+
+ For printing executable name excluding path from struct
+ task_struct.
+
+ Passed by reference.
+
+If you add other %p extensions, please extend lib/test_printf.c with
+one or more test cases, if at all feasible.
+
+
Thank you for your cooperation and attention.