The I2C specification explicitly describes both SDA and SCL as bidirectional lines. An I2C master with a read-only SCL is thus not compliant. If a slow slave stretches the clock, errors will happen, so the bus can't be considered as reliable.
Signed-off-by: Jean Delvare <[email protected]> --- drivers/i2c/algos/i2c-algo-bit.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) --- linux-2.6.37-rc5.orig/drivers/i2c/algos/i2c-algo-bit.c 2010-12-07 11:02:38.000000000 +0100 +++ linux-2.6.37-rc5/drivers/i2c/algos/i2c-algo-bit.c 2010-12-07 11:03:23.000000000 +0100 @@ -604,9 +604,10 @@ static int __i2c_bit_add_bus(struct i2c_ int (*add_adapter)(struct i2c_adapter *)) { struct i2c_algo_bit_data *bit_adap = adap->algo_data; + int ret; if (bit_test) { - int ret = test_bus(bit_adap, adap->name); + ret = test_bus(bit_adap, adap->name); if (ret < 0) return -ENODEV; } @@ -615,7 +616,16 @@ static int __i2c_bit_add_bus(struct i2c_ adap->algo = &i2c_bit_algo; adap->retries = 3; - return add_adapter(adap); + ret = add_adapter(adap); + if (ret < 0) + return ret; + + /* Complain if SCL can't be read */ + if (bit_adap->getscl == NULL) { + dev_warn(&adap->dev, "Not I2C compliant: can't read SCL\n"); + dev_warn(&adap->dev, "Bus may be unreliable\n"); + } + return 0; } int i2c_bit_add_bus(struct i2c_adapter *adap) -- Jean Delvare -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
