i2c: Split I2C_M_NOSTART support out of I2C_FUNC_PROTOCOL_MANGLING

Since there are uses for I2C_M_NOSTART which are much more sensible and
standard than most of the protocol mangling functionality (the main one
being gather writes to devices where something like a register address
needs to be inserted before a block of data) create a new I2C_FUNC_NOSTART
for this feature and update all the users to use it.

Also strengthen the disrecommendation of the protocol mangling while we're
at it.

In the case of regmap-i2c we remove the requirement for mangling as
I2C_M_NOSTART is the only mangling feature which is being used.

Signed-off-by: Mark Brown <[e-mail]>
Acked-by: Wolfram Sang <[e-mail]>
Signed-off-by: Jean Delvare <[e-mail]>

Documentation/i2c/functionality

···
                                   adapters typically can not do these)
   I2C_FUNC_10BIT_ADDR             Handles the 10-bit address extensions
   I2C_FUNC_PROTOCOL_MANGLING      Knows about the I2C_M_IGNORE_NAK,
-                                  I2C_M_REV_DIR_ADDR, I2C_M_NOSTART and
-                                  I2C_M_NO_RD_ACK flags (which modify the
-                                  I2C protocol!)
+                                  I2C_M_REV_DIR_ADDR and I2C_M_NO_RD_ACK
+                                  flags (which modify the I2C protocol!)
+  I2C_FUNC_NOSTART                Can skip repeated start sequence
   I2C_FUNC_SMBUS_QUICK            Handles the SMBus write_quick command
   I2C_FUNC_SMBUS_READ_BYTE        Handles the SMBus read_byte command
   I2C_FUNC_SMBUS_WRITE_BYTE       Handles the SMBus write_byte command
···
   I2C_FUNC_SMBUS_EMUL             Handles all SMBus commands than can be
                                   emulated by a real I2C adapter (using
                                   the transparent emulation layer)
+
+In kernel versions prior to 3.5 I2C_FUNC_NOSTART was implemented as
+part of I2C_FUNC_PROTOCOL_MANGLING.
 
 
 ADAPTER IMPLEMENTATION

Documentation/i2c/i2c-protocol

···
 Modified transactions
 =====================
 
-We have found some I2C devices that needs the following modifications:
+The following modifications to the I2C protocol can also be generated,
+with the exception of I2C_M_NOSTART these are usually only needed to
+work around device issues:
 
   Flag I2C_M_NOSTART: 
     In a combined transaction, no 'S Addr Wr/Rd [A]' is generated at some
···
     If you set the I2C_M_NOSTART variable for the first partial message,
     we do not generate Addr, but we do generate the startbit S. This will
     probably confuse all other clients on your bus, so don't try this.
+
+    This is often used to gather transmits from multiple data buffers in
+    system memory into something that appears as a single transfer to the
+    I2C device but may also be used between direction changes by some
+    rare devices.
 
   Flags I2C_M_REV_DIR_ADDR
     This toggles the Rd/Wr flag. That is, if you want to do a write, but

drivers/base/regmap/regmap-i2c.c

···
 	/* If the I2C controller can't do a gather tell the core, it
 	 * will substitute in a linear write for us.
 	 */
-	if (!i2c_check_functionality(i2c->adapter, I2C_FUNC_PROTOCOL_MANGLING))
+	if (!i2c_check_functionality(i2c->adapter, I2C_FUNC_NOSTART))
 		return -ENOTSUPP;
 
 	xfer[0].addr = i2c->addr;

drivers/i2c/algos/i2c-algo-bit.c

···
 
 static u32 bit_func(struct i2c_adapter *adap)
 {
-	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
+	return I2C_FUNC_I2C | I2C_FUNC_NOSTART | I2C_FUNC_SMBUS_EMUL |
 	       I2C_FUNC_SMBUS_READ_BLOCK_DATA |
 	       I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
 	       I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;

drivers/i2c/busses/i2c-nuc900.c

···
 /* declare our i2c functionality */
 static u32 nuc900_i2c_func(struct i2c_adapter *adap)
 {
-	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_PROTOCOL_MANGLING;
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_NOSTART |
+		I2C_FUNC_PROTOCOL_MANGLING;
 }
 
 /* i2c bus registration info */

drivers/i2c/busses/i2c-s3c2410.c

···
 /* declare our i2c functionality */
 static u32 s3c24xx_i2c_func(struct i2c_adapter *adap)
 {
-	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_PROTOCOL_MANGLING;
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_NOSTART |
+		I2C_FUNC_PROTOCOL_MANGLING;
 }
 
 /* i2c bus registration info */

drivers/input/joystick/as5011.c

···
 	}
 
 	if (!i2c_check_functionality(client->adapter,
+				     I2C_FUNC_NOSTART |
 				     I2C_FUNC_PROTOCOL_MANGLING)) {
 		dev_err(&client->dev,
 			"need i2c bus that supports protocol mangling\n");

drivers/video/matrox/matroxfb_maven.c

···
 
 	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_WORD_DATA |
 					      I2C_FUNC_SMBUS_BYTE_DATA |
+					      I2C_FUNC_NOSTART |
 					      I2C_FUNC_PROTOCOL_MANGLING))
 		goto ERROR0;
 	if (!(data = kzalloc(sizeof(*data), GFP_KERNEL))) {

include/linux/i2c.h

···
 	__u16 flags;
 #define I2C_M_TEN		0x0010	/* this is a ten bit chip address */
 #define I2C_M_RD		0x0001	/* read data, from slave to master */
-#define I2C_M_NOSTART		0x4000	/* if I2C_FUNC_PROTOCOL_MANGLING */
+#define I2C_M_NOSTART		0x4000	/* if I2C_FUNC_NOSTART */
 #define I2C_M_REV_DIR_ADDR	0x2000	/* if I2C_FUNC_PROTOCOL_MANGLING */
 #define I2C_M_IGNORE_NAK	0x1000	/* if I2C_FUNC_PROTOCOL_MANGLING */
 #define I2C_M_NO_RD_ACK		0x0800	/* if I2C_FUNC_PROTOCOL_MANGLING */
···
 
 #define I2C_FUNC_I2C			0x00000001
 #define I2C_FUNC_10BIT_ADDR		0x00000002
-#define I2C_FUNC_PROTOCOL_MANGLING	0x00000004 /* I2C_M_NOSTART etc. */
+#define I2C_FUNC_PROTOCOL_MANGLING	0x00000004 /* I2C_M_IGNORE_NAK etc. */
 #define I2C_FUNC_SMBUS_PEC		0x00000008
+#define I2C_FUNC_NOSTART		0x00000010 /* I2C_M_NOSTART */
 #define I2C_FUNC_SMBUS_BLOCK_PROC_CALL	0x00008000 /* SMBus 2.0 */
 #define I2C_FUNC_SMBUS_QUICK		0x00010000
 #define I2C_FUNC_SMBUS_READ_BYTE	0x00020000