On Mon, Feb 09, 2009 at 05:17:20PM +0100, Jean Delvare wrote:
> On Fri, 6 Feb 2009 16:23:17 +0100, Rodolfo Giometti wrote:
> > It could happen that an i2c adapter may lock the bus due due
>
> Typo: "due due" -> "due to".
Ok.
> > electrical problems, so the user may recover this stale state by using:
> >
> > $ echo 1 > /sys/class/i2c-adapter/i2c-0/reset
>
> What is the intended purpose, debugging? I would certainly hope that
> drivers know by themselves when they need a reset. Requiring users to
> reset themselves doesn't sound terribly friendly :(
Unluckely not all adapter does it by themselfes! At least not PXA
one. I'm currently work on adding this new feature.
> > Signed-off-by: Rodolfo Giometti <giometti@xxxxxxxx>
> > ---
> > drivers/i2c/i2c-core.c | 21 +++++++++++++++++++++
> > include/linux/i2c.h | 2 ++
> > 2 files changed, 23 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> > index b1c9abe..b0c4053 100644
> > --- a/drivers/i2c/i2c-core.c
> > +++ b/drivers/i2c/i2c-core.c
> > @@ -393,8 +393,29 @@ show_adapter_name(struct device *dev, struct device_attribute *attr, char *buf)
> > return sprintf(buf, "%s\n", adap->name);
> > }
> >
> > +static ssize_t
> > +write_adapter_reset(struct device *dev, struct device_attribute *attr,
> > + const char *buf, size_t count)
> > +{
> > + struct i2c_adapter *adap = to_i2c_adapter(dev);
> > + unsigned long val;
> > + int ret;
> > +
> > + if (!adap->reset)
> > + return -EINVAL;
> > +
> > + ret = strict_strtoul(buf, 10, &val);
> > + if (ret || val != 1)
> > + return -EINVAL;
> > +
> > + adap->reset(adap);
>
> I consider it good practice to always test for function pointers
> _right_ before dereferencing them. Makes it harder to accidentally
> break things later.
Ok.
> > +
> > + return count;
> > +}
> > +
> > static struct device_attribute i2c_adapter_attrs[] = {
> > __ATTR(name, S_IRUGO, show_adapter_name, NULL),
> > + __ATTR(reset, S_IWUSR, NULL, write_adapter_reset),
> > { },
> > };
> >
> > diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> > index fcfbfea..0f84345 100644
> > --- a/include/linux/i2c.h
> > +++ b/include/linux/i2c.h
> > @@ -369,6 +369,8 @@ struct i2c_adapter {
> > struct list_head clients; /* DEPRECATED */
> > char name[48];
> > struct completion dev_released;
> > +
> > + void (*reset)(struct i2c_adapter *); /* user request adap reset */
> > };
> > #define to_i2c_adapter(d) container_of(d, struct i2c_adapter, dev)
> >
I'll repropose a new patch ASAP.
Ciao,
Rodolfo
--
GNU/Linux Solutions e-mail: giometti@xxxxxxxxxxxx
Linux Device Driver giometti@xxxxxxxx
Embedded Systems phone: +39 349 2432127
UNIX programming skype: rodolfo.giometti
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