From: David Brownell Subject: i2c-algo-bit: Fix NAK/ARB comments Update comments and logging on return path for byte writes. NAK is an error, to be reported or optionally ignored. Timeouts are always errors. Lost arbitration is not currently handled, so don't even list it as an option in the error message. Don't return bogus EFAULT code for inappropriate NAK; EIO is better, there is no bad userspace address in question. Signed-off-by: David Brownell Signed-off-by: Jean Delvare --- drivers/i2c/algos/i2c-algo-bit.c | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-) --- linux-2.6.24-rc2.orig/drivers/i2c/algos/i2c-algo-bit.c 2007-11-09 22:32:17.000000000 +0100 +++ linux-2.6.24-rc2/drivers/i2c/algos/i2c-algo-bit.c 2007-11-09 22:32:55.000000000 +0100 @@ -357,10 +357,26 @@ static int sendbytes(struct i2c_adapter count--; temp++; wrcount++; - } else { /* arbitration or no acknowledge */ - dev_err(&i2c_adap->dev, "sendbytes: error - bailout.\n"); - return (retval<0)? retval : -EFAULT; - /* got a better one ?? */ + + /* A slave NAKing the master means the slave didn't like + * something about the data it saw. For example, maybe + * the SMBus PEC was wrong. + */ + } else if (retval == 0) { + dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.\n"); + return -EIO; + + /* Timeout; or (someday) lost arbitration + * + * FIXME Lost ARB implies retrying the transaction from + * the first message, after the "winning" master issues + * its STOP. As a rule, upper layer code has no reason + * to know or care about this ... it is *NOT* an error. + */ + } else { + dev_err(&i2c_adap->dev, "sendbytes: error %d\n", + retval); + return retval; } } return wrcount;