> -----Original Message-----
> From: Guenter Roeck [mailto:li...@roeck-us.net]
> Sent: Tuesday, June 26, 2018 7:33 PM
> To: Vadim Pasternak <vad...@mellanox.com>
> Cc: Andrew Lunn <and...@lunn.ch>; da...@davemloft.net;
> netdev@vger.kernel.org; rui.zh...@intel.com; edubez...@gmail.com;
> j...@resnulli.us; mlxsw <ml...@mellanox.com>; Michael Shych
> <michae...@mellanox.com>
> Subject: Re: [patch net-next RFC 11/12] mlxsw: core: Extend hwmon interface
> with FAN fault attribute
>
> On Tue, Jun 26, 2018 at 02:47:01PM +0000, Vadim Pasternak wrote:
> >
> >
> > > -----Original Message-----
> > > From: Andrew Lunn [mailto:and...@lunn.ch]
> > > Sent: Tuesday, June 26, 2018 5:29 PM
> > > To: Vadim Pasternak <vad...@mellanox.com>
> > > Cc: da...@davemloft.net; netdev@vger.kernel.org; li...@roeck-us.net;
> > > rui.zh...@intel.com; edubez...@gmail.com; j...@resnulli.us; mlxsw
> > > <ml...@mellanox.com>; Michael Shych <michae...@mellanox.com>
> > > Subject: Re: [patch net-next RFC 11/12] mlxsw: core: Extend hwmon
> > > interface with FAN fault attribute
> > >
> > > > +static ssize_t mlxsw_hwmon_fan_fault_show(struct device *dev,
> > > > + struct device_attribute *attr,
> > > > + char *buf)
> > > > +{
> > > > + struct mlxsw_hwmon_attr *mlwsw_hwmon_attr =
> > > > + container_of(attr, struct mlxsw_hwmon_attr,
> > > dev_attr);
> > > > + struct mlxsw_hwmon *mlxsw_hwmon = mlwsw_hwmon_attr->hwmon;
> > > > + char mfsm_pl[MLXSW_REG_MFSM_LEN];
> > > > + u16 tach;
> > > > + int err;
> > > > +
> > > > + mlxsw_reg_mfsm_pack(mfsm_pl, mlwsw_hwmon_attr->type_index);
> > > > + err = mlxsw_reg_query(mlxsw_hwmon->core, MLXSW_REG(mfsm),
> > > mfsm_pl);
> > > > + if (err) {
> > > > + dev_err(mlxsw_hwmon->bus_info->dev, "Failed to query
> > > fan\n");
> > > > + return err;
> > > > + }
> > > > + tach = mlxsw_reg_mfsm_rpm_get(mfsm_pl);
> > > > +
> > > > + return sprintf(buf, "%u\n", (tach < mlxsw_hwmon->tach_min) ? 1 :
> > > > +0); }
> > >
> > > Documentation/hwmon/sysfs-interface says:
> > >
> > > Alarms are direct indications read from the chips. The drivers do
> > > NOT make comparisons of readings to thresholds. This allows
> > > violations between readings to be caught and alarmed. The exact
> > > definition of an alarm (for example, whether a threshold must be met
> > > or must be exceeded to cause an alarm) is chip-dependent.
> > >
> > > Now, this is a fault, not an alarm. But does the same apply?
> >
> Yes, it does. There are no "soft" alarms / faults.
>
> > Hi Andrew,
> >
> > Hardware provides minimum value for tachometer.
> > Tachometer is considered as faulty in case it's below this value.
>
> This is for user space to decide, not for the kernel.
Hi Guenter,
Do you suggest to expose provide fan{x}_min, instead of fan{x}_fault
and give to user to compare fan{x}_input versus fan{x}_min for the
fault decision?
>
> > In case any tachometer is faulty, PWM according to the system
> > requirements should be set to 100% until the fault
>
> system requirements. Again, this is for user space to decide.
Yes, user should decide in this case and I wanted to provide to user
fan{x}_fault for this matter. But it could do it based on input and min
attributes, of course.
>
> > is not recovered (f.e. by physical replacing of bad unit).
> > This is the motivation to expose fan{x}_fault in the way it's exposed.
> >
> > Thanks,
> > Vadim.
> >
> > >
> > > Andrew
