[PATCH] vsprintf: add Bluetooth UUID %pU[rR] format specifier

[PATCH] vsprintf: add Bluetooth UUID %pU[rR] format specifier

[Marcel Holtmann]

The Bluetooth UUID is used in big endian reversed order. Add new
modifier to print a UUID in big endian, but where the input byte
stream is actually in reversed order.

This is similar to %pMR that allows to print a MAC address in
reversed order since that is how the Bluetooth BD_ADDR is
actually represented in a byte stream.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
---
 Documentation/printk-formats.txt |  6 ++++++
 lib/vsprintf.c                   | 20 +++++++++++++++++---
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt
index 445ad74..1fd0e43 100644
--- a/Documentation/printk-formats.txt
+++ b/Documentation/printk-formats.txt
@@ -159,12 +159,18 @@ UUID/GUID addresses:
 	%pUB	00010203-0405-0607-0809-0A0B0C0D0E0F
 	%pUl	03020100-0504-0706-0809-0a0b0c0e0e0f
 	%pUL	03020100-0504-0706-0809-0A0B0C0E0E0F
+	%pUr	0f0e0d0c-0b0a-0908-0706-050403020100
+	%pUR	0F0E0D0C-0B0A-0908-0706-050403020100
 
 	For printing 16-byte UUID/GUIDs addresses. The additional 'l', 'L',
 	'b' and 'B' specifiers are used to specify a little endian order in
 	lower ('l') or upper case ('L') hex characters - and big endian order
 	in lower ('b') or upper case ('B') hex characters.
 
+	The additional 'r' and 'R' specifiers are used to specify reversed
+	big endian order in either lower ('r') or upper case ('R') hex
+	characters. This is useful for Bluetooth UUID addresses.
+
 	Where no additional specifiers are used the default little endian
 	order with lower case hex characters will be printed.
 
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 26559bd..ea9b76c 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1106,6 +1106,7 @@ char *uuid_string(char *buf, char *end, const u8 *addr,
 	static const u8 le[16] = {3,2,1,0,5,4,7,6,8,9,10,11,12,13,14,15};
 	const u8 *index = be;
 	bool uc = false;
+	bool reversed = false;
 
 	switch (*(++fmt)) {
 	case 'L':
@@ -1116,10 +1117,19 @@ char *uuid_string(char *buf, char *end, const u8 *addr,
 	case 'B':
 		uc = true;
 		break;
+	case 'R':
+		uc = true;		/* fall-through */
+	case 'r':
+		reversed = true;
+		break;
 	}
 
 	for (i = 0; i < 16; i++) {
-		p = hex_byte_pack(p, addr[index[i]]);
+		if (reversed)
+			p = hex_byte_pack(p, addr[index[15 - i]]);
+		else
+			p = hex_byte_pack(p, addr[index[i]]);
+
 		switch (i) {
 		case 3:
 		case 5:
@@ -1199,10 +1209,14 @@ int kptr_restrict __read_mostly;
  *         B big endian UPPER case hex
  *         l little endian lower case hex
  *         L little endian UPPER case hex
+ *         r big endian lower case hex, reverse order (Bluetooth)
+ *         R big endian UPPER case hex, reverse order (Bluetooth)
  *           big endian output byte order is:
  *             [0][1][2][3]-[4][5]-[6][7]-[8][9]-[10][11][12][13][14][15]
  *           little endian output byte order is:
  *             [3][2][1][0]-[5][4]-[7][6]-[8][9]-[10][11][12][13][14][15]
+ *           big endian, reverse order output byte order is:
+ *             [15][14][13][12]-[11][10]-[9][8]-[7][6]-[5][4][3][2][1][0]
  * - 'V' For a struct va_format which contains a format string * and va_list *,
  *       call vsnprintf(->format, *->va_list).
  *       Implements a "recursive vsnprintf".
@@ -1572,8 +1586,8 @@ qualifier:
  * %pI6c print an IPv6 address as specified by RFC 5952
  * %pIS depending on sa_family of 'struct sockaddr *' print IPv4/IPv6 address
  * %piS depending on sa_family of 'struct sockaddr *' print IPv4/IPv6 address
- * %pU[bBlL] print a UUID/GUID in big or little endian using lower or upper
- *   case.
+ * %pU[bBlLrR] print a UUID/GUID in big or little endian or reversed order
+ *   big endian using lower or upper case.
  * %*ph[CDN] a variable-length hex string with a separator (supports up to 64
  *           bytes of the input)
  * %n is ignored
-- 
1.8.3.1

Re: [PATCH] vsprintf: add Bluetooth UUID %pU[rR] format specifier

[Joe Perches]

On Sat, 2013-10-19 at 09:25 -0700, Marcel Holtmann wrote:
> The Bluetooth UUID is used in big endian reversed order. Add new
> modifier to print a UUID in big endian, but where the input byte
> stream is actually in reversed order.
> This is similar to %pMR that allows to print a MAC address in
> reversed order since that is how the Bluetooth BD_ADDR is
> actually represented in a byte stream.

Seems sensible.  Other than print_bt_uuid, is
there another place where will it be used?

Are you going to convert print_bt_uuid to use this?

> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
[]
> @@ -1106,6 +1106,7 @@ char *uuid_string(char *buf, char *end, const u8 *addr,
>  	static const u8 le[16] = {3,2,1,0,5,4,7,6,8,9,10,11,12,13,14,15};
>  	const u8 *index = be;
>  	bool uc = false;
> +	bool reversed = false;
>  
>  	switch (*(++fmt)) {

Could there ever be a little endian reversed UUID?

Might it be useful to change this to:

	while (isalpha(*++fmt)) {
		switch (*fmt) {

etc?

Re: [PATCH] vsprintf: add Bluetooth UUID %pU[rR] format specifier

[Marcel Holtmann]

Hi Joe,

>> The Bluetooth UUID is used in big endian reversed order. Add new
>> modifier to print a UUID in big endian, but where the input byte
>> stream is actually in reversed order.
>> This is similar to %pMR that allows to print a MAC address in
>> reversed order since that is how the Bluetooth BD_ADDR is
>> actually represented in a byte stream.
> 
> Seems sensible.  Other than print_bt_uuid, is
> there another place where will it be used?
> 
> Are you going to convert print_bt_uuid to use this?

my plan is to convert this one when this modifier gets upstream.

>> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> []
>> @@ -1106,6 +1106,7 @@ char *uuid_string(char *buf, char *end, const u8 *addr,
>> 	static const u8 le[16] = {3,2,1,0,5,4,7,6,8,9,10,11,12,13,14,15};
>> 	const u8 *index = be;
>> 	bool uc = false;
>> +	bool reversed = false;
>> 
>> 	switch (*(++fmt)) {
> 
> Could there ever be a little endian reversed UUID?

I honestly do not know. I looked at the little endian one and it looked a bit heavy misplaced if we would use a reversed stream of bytes.

> Might it be useful to change this to:
> 
> 	while (isalpha(*++fmt)) {
> 		switch (*fmt) {

I didn't do it so the modifier didn't get any longer than it needs to be.

Regards

Marcel

Re: [PATCH] vsprintf: add Bluetooth UUID %pU[rR] format specifier

[Joe Perches]

On Sun, 2013-10-20 at 00:30 +0200, Marcel Holtmann wrote:
> Hi Joe,

Hi Marcel

> > Could there ever be a little endian reversed UUID?
> I honestly do not know. I looked at the little endian one and it
> looked a bit heavy misplaced if we would use a reversed stream of
> bytes.
> > Might it be useful to change this to:
> > 
> > 	while (isalpha(*++fmt)) {
> > 		switch (*fmt) {
> 
> I didn't do it so the modifier didn't get any longer than it needs to be.

Given that %pU is big endian by default, then the modifier
doesn't have to get longer.  %pUR and %pUr would still be
big endian and this would simply allow %pULR if necessary.

cheers, Joe