i2c-powermac: Reject unsupported I2C transactions

The i2c-powermac driver doesn't support arbitrary multi-message I2C
transactions, only SMBus ones. Make it clear by returning an error if
a multi-message I2C transaction is attempted. This is better than only
processing the first message, because most callers won't recover from
the short transaction. Anyone wishing to issue multi-message
transactions should use the SMBus API instead of the raw I2C API.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Tested-by: Michel Daenzer <michel@daenzer.net>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/i2c/busses/i2c-powermac.c b/drivers/i2c/busses/i2c-powermac.c
index 3c9d71f60187..a74f3bab05b8 100644
--- a/drivers/i2c/busses/i2c-powermac.c
+++ b/drivers/i2c/busses/i2c-powermac.c
@@ -146,6 +146,12 @@ static int i2c_powermac_master_xfer(	struct i2c_adapter *adap,
         int                     read;
         int                     addrdir;
 
+        if (num != 1) {
+                dev_err(&adap->dev,
+                        "Multi-message I2C transactions not supported\n");
+                return -EOPNOTSUPP;
+        }
+
         if (msgs->flags & I2C_M_TEN)
                 return -EINVAL;
         read = (msgs->flags & I2C_M_RD) != 0;