i2c: smbus: add unlocked __i2c_smbus_xfer variant

Removes all locking from i2c_smbus_xfer and renames it to __i2c_smbus_xfer,
then adds a new i2c_smbus_xfer function that simply grabs the lock while
calling the unlocked variant.

This is not perfectly equivalent, since i2c_smbus_xfer was callable from
atomic/irq context if you happened to end up emulating SMBus with an I2C
transfer, and that is no longer the case with this patch. It is unknown
(to me) if anything depends on that quirk, but it seems fragile enough to
simply break those cases and require them to call i2c_transfer directly
instead.

While at it, for consistency rename the 2nd to last argument (size) of
the i2c_smbus_xfer declaration to protocol and remove the surplus extern
marker.

Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

1 files changed, 20 insertions, 8 deletions

diff --git a/drivers/i2c/i2c-core-smbus.c b/drivers/i2c/i2c-core-smbus.c
index 51970bae3c4a..9cd66cabb84f 100644
--- a/drivers/i2c/i2c-core-smbus.c
+++ b/drivers/i2c/i2c-core-smbus.c
@@ -463,7 +463,7 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr,
 			msg[num-1].len++;
 	}
 
-	status = i2c_transfer(adapter, msg, num);
+	status = __i2c_transfer(adapter, msg, num);
 	if (status < 0)
 		goto cleanup;
 	if (status != num) {
@@ -524,9 +524,24 @@ cleanup:
  * This executes an SMBus protocol operation, and returns a negative
  * errno code else zero on success.
  */
-s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags,
-		   char read_write, u8 command, int protocol,
-		   union i2c_smbus_data *data)
+s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr,
+		   unsigned short flags, char read_write,
+		   u8 command, int protocol, union i2c_smbus_data *data)
+{
+	s32 res;
+
+	i2c_lock_bus(adapter, I2C_LOCK_SEGMENT);
+	res = __i2c_smbus_xfer(adapter, addr, flags, read_write,
+			       command, protocol, data);
+	i2c_unlock_bus(adapter, I2C_LOCK_SEGMENT);
+
+	return res;
+}
+EXPORT_SYMBOL(i2c_smbus_xfer);
+
+s32 __i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr,
+		     unsigned short flags, char read_write,
+		     u8 command, int protocol, union i2c_smbus_data *data)
 {
 	unsigned long orig_jiffies;
 	int try;
@@ -543,8 +558,6 @@ s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags,
 	flags &= I2C_M_TEN | I2C_CLIENT_PEC | I2C_CLIENT_SCCB;
 
 	if (adapter->algo->smbus_xfer) {
-		i2c_lock_bus(adapter, I2C_LOCK_SEGMENT);
-
 		/* Retry automatically on arbitration loss */
 		orig_jiffies = jiffies;
 		for (res = 0, try = 0; try <= adapter->retries; try++) {
@@ -557,7 +570,6 @@ s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags,
 				       orig_jiffies + adapter->timeout))
 				break;
 		}
-		i2c_unlock_bus(adapter, I2C_LOCK_SEGMENT);
 
 		if (res != -EOPNOTSUPP || !adapter->algo->master_xfer)
 			goto trace;
@@ -579,7 +591,7 @@ trace:
 
 	return res;
 }
-EXPORT_SYMBOL(i2c_smbus_xfer);
+EXPORT_SYMBOL(__i2c_smbus_xfer);
 
 /**
  * i2c_smbus_read_i2c_block_data_or_emulated - read block or emulate