Hi Ben,
On Tue, 7 Dec 2010 11:53:25 +0000, Ben Dooks wrote:
> 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.
And I thought you were a busy developer ;)
There is no trend one way or another, neither in the kernel tree nor
even in drivers/i2c specifically.
> > + 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?
I'm not sure what "scan" you refer to, and in all honesty I'm not sure
I get your point at all.
--
Jean Delvare
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