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| author | Jean Delvare <khali@linux-fr.org> | 2011-01-10 22:11:23 +0100 |
|---|---|---|
| committer | Jean Delvare <khali@endymion.delvare> | 2011-01-10 22:11:23 +0100 |
| commit | af5a60baaee66e2f891dbb9a8519ca28ab7da7cd (patch) | |
| tree | b2dc270ce64b4ad9779d1f3a013a96cfb7ab069e /drivers/i2c/algos | |
| parent | f451171c5ac829e55581c81caf2cb01e1c0a5c5f (diff) | |
| download | lwn-af5a60baaee66e2f891dbb9a8519ca28ab7da7cd.tar.gz lwn-af5a60baaee66e2f891dbb9a8519ca28ab7da7cd.zip | |
i2c-algo-bit: Complain about masters which can't read SCL
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 <khali@linux-fr.org>
Diffstat (limited to 'drivers/i2c/algos')
| -rw-r--r-- | drivers/i2c/algos/i2c-algo-bit.c | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/drivers/i2c/algos/i2c-algo-bit.c b/drivers/i2c/algos/i2c-algo-bit.c index 938170b8998b..38319a69bd0a 100644 --- a/drivers/i2c/algos/i2c-algo-bit.c +++ b/drivers/i2c/algos/i2c-algo-bit.c @@ -604,9 +604,10 @@ static int __i2c_bit_add_bus(struct i2c_adapter *adap, 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_adapter *adap, 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) |