2 files changed, 24 insertions, 4 deletions

diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt
index 5df176ed59b8..d8d168fa79d6 100644
--- a/Documentation/printk-formats.txt
+++ b/Documentation/printk-formats.txt
@@ -56,6 +56,7 @@ Struct Resources:
 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
 
@@ -67,6 +68,10 @@ MAC/FDDI addresses:
         the 'M' specifier to use dash ('-') separators instead of the default
         separator.
 
+        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.
+
 IPv4 addresses:
 
         %pI4    1.2.3.4
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index c3f36d415bdf..736974576e2d 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -662,15 +662,28 @@ char *mac_address_string(char *buf, char *end, u8 *addr,
         char *p = mac_addr;
         int i;
         char separator;
+        bool reversed = false;
 
-        if (fmt[1] == 'F') {            /* FDDI canonical format */
+        switch (fmt[1]) {
+        case 'F':
                 separator = '-';
-        } else {
+                break;
+
+        case 'R':
+                reversed = true;
+                /* fall through */
+
+        default:
                 separator = ':';
+                break;
         }
 
         for (i = 0; i < 6; i++) {
-                p = hex_byte_pack(p, addr[i]);
+                if (reversed)
+                        p = hex_byte_pack(p, addr[5 - i]);
+                else
+                        p = hex_byte_pack(p, addr[i]);
+
                 if (fmt[0] == 'M' && i != 5)
                         *p++ = separator;
         }
@@ -933,6 +946,7 @@ int kptr_restrict __read_mostly;
  * - 'm' For a 6-byte MAC address, it prints the hex address without colons
  * - '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)
  * - '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
@@ -995,7 +1009,8 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
                 return resource_string(buf, end, ptr, spec, fmt);
         case 'M':                       /* Colon separated: 00:01:02:03:04:05 */
         case 'm':                       /* Contiguous: 000102030405 */
-                                        /* [mM]F (FDDI, bit reversed) */
+                                        /* [mM]F (FDDI) */
+                                        /* [mM]R (Reverse order; Bluetooth) */
                 return mac_address_string(buf, end, ptr, spec, fmt);
         case 'I':                       /* Formatted IP supported
                                          * 4:   1.2.3.4