Re: [lm-sensors] pmbus driver

[Guenter Roeck <guenter.roeck@ericsson.com>]

On Thu, Jun 23, 2011 at 05:15:52AM -0400, Vivek Bardia wrote:
> On 22 June 2011 15:12, Guenter Roeck <guenter.roeck@ericsson.com> wrote:
> >
> > On Wed, Jun 22, 2011 at 04:45:14AM -0400, Vivek Bardia wrote:
> > > Hi Guenter,
> > >
> > > sorry for the delayed reply from my end.
> > >
> > > Right now I am under the constraint where I cannot share the datasheet. But
> > > yes, the datasheet is going be out very soon. I shall update u about the same
> > >
> > > Can the pmbus driver be used to set output voltage from another driver in the
> > > kernel space itself. what I understood about the pmbus driver is that it is
> > > meant for monitoring and controlling. at my end if the monitoring is being done
> > > by another entity(voltage regulator) and the controlling only needs to be done
> > > by the PMIC then how do I go about? say I just want to use VOUT_TRIM command.
> > >
> > At least right now that is not supported. The current driver only supports hwmon
> > functionality, ie pure monitoring; control is not implemented. A clean implementation
> > for control would probably require a rewrite with a generic part (probably in mfd),
> > control (probably in regulator) and monitoring (in hwmon).
> 
> But you do have pmbus_write_byte/pmbus_write_word_data calls. They are
> only not exported right?
> or is it that if these calls are made, it wont work the way it should
> 
Those are of no benefit outside the driver.

> > Note that you can not have an I2C slave chip controlled by multiple entities.
> > If you wrote or have a regulator driver, it has control over the chip, and hwmon access
> > to it will not be possible.
> 
> what if I simply do not need any monitoring capabilities. I just want
> to enable the device(OPERATION), read the output voltage(READ_VOUT)
> and then based on an external custom sensor set the output
> voltage(VOUT_TRIM), once done disable the device.
> 
Not sure what value that has, since you disable the device afterwards anyway ...
guess I don't have to know ;).

You can write the registers directly using i2c function calls, i2c_smbus_write_byte()
and i2c_smbus_write_word_data(). If your chip has a page command, just set the page first.

Thanks,
Guenter

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