[PATCH v4 1/2] vsprintf: Add %p[mM]U for uppercase MAC address

[Konrad Gräfe]

The CDC-ECM specification requires an USB gadget to send the host MAC
address as uppercase hex string. This change adds the appropriate
modifier.

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Konrad Gräfe <k.graefe@xxxxxxxxxxx>
---

Changes since v3:
* Added documentation
* Added test cases
* Use string_upper() after conversion to simplify conversion loop
* Fixed maybe-uninitalized variable warning

Added in v3

 Documentation/core-api/printk-formats.rst | 15 ++++++++++-----
 lib/test_printf.c                         |  2 ++
 lib/vsprintf.c                            |  5 +++++
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst
index dbe1aacc79d0..1ec682bdfe94 100644
--- a/Documentation/core-api/printk-formats.rst
+++ b/Documentation/core-api/printk-formats.rst
@@ -298,11 +298,13 @@ MAC/FDDI addresses
 
 ::
 
-	%pM	00:01:02:03:04:05
-	%pMR	05:04:03:02:01:00
-	%pMF	00-01-02-03-04-05
-	%pm	000102030405
-	%pmR	050403020100
+	%pM	00:01:02:03:aa:bb
+	%pMR	aa:bb:03:02:01:00
+	%pMF	00-01-02-03-aa-bb
+	%pMU	00:01:02:03:AA:BB
+	%pm	00010203aabb
+	%pmR	bbaa03020100
+	%pmU	00010203AABB
 
 For printing 6-byte MAC/FDDI addresses in hex notation. The ``M`` and ``m``
 specifiers result in a printed address with (M) or without (m) byte
@@ -316,6 +318,9 @@ For Bluetooth addresses the ``R`` specifier shall be used after the ``M``
 specifier to use reversed byte order suitable for visual interpretation
 of Bluetooth addresses which are in the little endian order.
 
+For uppercase hex notation the ``U`` specifier shall be used after the ``M``
+and ``m`` specifiers.
+
 Passed by reference.
 
 IPv4 addresses
diff --git a/lib/test_printf.c b/lib/test_printf.c
index 46b4e6c414a3..7f4de2ecafbc 100644
--- a/lib/test_printf.c
+++ b/lib/test_printf.c
@@ -416,9 +416,11 @@ mac(void)
 	const u8 addr[6] = {0x2d, 0x48, 0xd6, 0xfc, 0x7a, 0x05};
 
 	test("2d:48:d6:fc:7a:05", "%pM", addr);
+	test("2D:48:D6:FC:7A:05", "%pMU", addr);
 	test("05:7a:fc:d6:48:2d", "%pMR", addr);
 	test("2d-48-d6-fc-7a-05", "%pMF", addr);
 	test("2d48d6fc7a05", "%pm", addr);
+	test("2D48D6FC7A05", "%pmU", addr);
 	test("057afcd6482d", "%pmR", addr);
 }
 
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index be71a03c936a..c82616c335e0 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1301,6 +1301,9 @@ char *mac_address_string(char *buf, char *end, u8 *addr,
 	}
 	*p = '\0';
 
+	if (fmt[1] == 'U')
+		string_upper(mac_addr, mac_addr);
+
 	return string_nocheck(buf, end, mac_addr, spec);
 }
 
@@ -2280,6 +2283,7 @@ char *rust_fmt_argument(char *buf, char *end, void *ptr);
  * - 'MF' For a 6-byte MAC FDDI address, it prints the address
  *       with a dash-separated hex notation
  * - '[mM]R' For a 6-byte MAC address, Reverse order (Bluetooth)
+ * - '[mM]U' For a 6-byte MAC address in uppercase hex
  * - 'I' [46] for IPv4/IPv6 addresses printed in the usual way
  *       IPv4 uses dot-separated decimal without leading 0's (1.2.3.4)
  *       IPv6 uses colon separated network-order 16 bit hex with leading 0's
@@ -2407,6 +2411,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
 	case 'M':			/* Colon separated: 00:01:02:03:04:05 */
 	case 'm':			/* Contiguous: 000102030405 */
 					/* [mM]F (FDDI) */
+					/* [mM]U (Uppercase hex) */
 					/* [mM]R (Reverse order; Bluetooth) */
 		return mac_address_string(buf, end, ptr, spec, fmt);
 	case 'I':			/* Formatted IP supported
-- 
2.34.1