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".
> 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 :(
> 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.
> +
> + 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)
>
--
Jean Delvare
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