On Tue, Dec 07, 2010 at 11:07:05AM +0100, Jean Delvare wrote:
> 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@xxxxxxxxxxxx>
> ---
> 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");
I'll have a think about wording. I might be able to improve it.
As a note, I always prefer cannot to can't.
> + dev_warn(&adap->dev, "Bus may be unreliable\n");
if there are any other warnings, should we print just one unreliable warning
at the end of the scan?
--
Ben
Q: What's a light-year?
A: One-third less calories than a regular year.
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