vsprintf: Add %p extension "%pOF" for device tree

90% of the usage of device node's full_name is printing it out in a
kernel message. However, storing the full path for every node is
wasteful and redundant. With a custom format specifier, we can generate
the full path at run-time and eventually remove the full path from every
node.

For instance typical use is:
	pr_info("Frobbing node %s\n", node->full_name);

Which can be written now as:
	pr_info("Frobbing node %pOF\n", node);

'%pO' is the base specifier to represent kobjects with '%pOF'
representing struct device_node. Currently, struct device_node is the
only supported type of kobject.

More fine-grained control of formatting includes printing the name,
flags, path-spec name and others, explained in the documentation entry.

Originally written by Pantelis, but pretty much rewrote the core
function using existing string/number functions. The 2 passes were
unnecessary and have been removed. Also, updated the checkpatch.pl
check. The unittest code was written by Grant Likely.

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
Acked-by: Joe Perches <joe@perches.com>
Signed-off-by: Rob Herring <robh@kernel.org>

1 files changed, 36 insertions, 0 deletions

diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt
index 5962949..619cdff 100644
--- a/Documentation/printk-formats.txt
+++ b/Documentation/printk-formats.txt
@@ -275,6 +275,42 @@ struct va_format:
 
 	Passed by reference.
 
+kobjects:
+	%pO
+
+	Base specifier for kobject based structs. Must be followed with
+	character for specific type of kobject as listed below:
+
+	Device tree nodes:
+
+	%pOF[fnpPcCF]
+
+	For printing device tree nodes. The optional arguments are:
+	    f device node full_name
+	    n device node name
+	    p device node phandle
+	    P device node path spec (name + @unit)
+	    F device node flags
+	    c major compatible string
+	    C full compatible string
+	Without any arguments prints full_name (same as %pOFf)
+	The separator when using multiple arguments is ':'
+
+	Examples:
+
+	%pOF	/foo/bar@0			- Node full name
+	%pOFf	/foo/bar@0			- Same as above
+	%pOFfp	/foo/bar@0:10			- Node full name + phandle
+	%pOFfcF	/foo/bar@0:foo,device:--P-	- Node full name +
+	                                          major compatible string +
+						  node flags
+							D - dynamic
+							d - detached
+							P - Populated
+							B - Populated bus
+
+	Passed by reference.
+
 struct clk:
 
 	%pC	pll1