Re: [PATCH v2 1/2] iio: ina2xx: add support for TI INA2xx Power Monitors

[Marc Titinger]

On 02/12/2015 17:04, Guenter Roeck wrote:
> On 12/02/2015 02:20 AM, Marc Titinger wrote:
> > On 02/12/2015 03:14, Guenter Roeck wrote:
> > > On Mon, Nov 30, 2015 at 12:49:14PM +0100, Marc Titinger wrote:
> > > > in SOFTWARE buffer mode, a kthread will capture the active
> > > > scan_elements
> > > > into a kfifo, then compute the remaining time until the next capture
> > > > tick
> > > > and do an active wait (udelay).
> > > >
> > > > This will produce a stream of up to fours channels plus a 64bits
> > > > timestamps (ns).
> > > >
> > > > Tested with ina226, on BeagleBoneBlack.
> > > >
> > > > Datasheet: http://www.ti.com/lit/gpn/ina226
> > > >
> > > > Signed-off-by: Marc Titinger <mtitinger@xxxxxxxxxxxx>
> > > > ---
> > > >   drivers/iio/adc/Kconfig      |   9 +
> > > >   drivers/iio/adc/Makefile     |   1 +
> > > >   drivers/iio/adc/ina2xx-iio.c | 678
> > > > +++++++++++++++++++++++++++++++++++++++++++
> > > >   3 files changed, 688 insertions(+)
> > > >   create mode 100644 drivers/iio/adc/ina2xx-iio.c
> > > > +
> > > [ ... ]
> > > > +
> > > > +static const struct i2c_device_id ina2xx_id[] = {
> > > > +    {"ina219", ina219},
> > > > +    {"ina220", ina219},
> > > > +    {"ina226", ina226},
> > > > +    {"ina230", ina226},
> > > > +    {"ina231", ina226},
> > > > +    {}
> > > > +};
> > >
> > > I wonder what is going to happen if both this driver and the hwmon
> > > driver for the same chips are configured in a system which supports
> > > devicetree (or any system, really). Unless I am missing something,
> > > the result will be that both drivers will try to instantiate, and
> > > one will fail with -EBUSY. Or the instantiated driver is more or less
> > > random, depending on which one happens to be loaded. Not a good
> > > situation to be in.
> >
> > I agree, we should put a mutual exclusion in Kconfig, plus maybe a
> > cross-reference in the help section.
> >
> > > For the time being, it might make sense to add cross-dependencies
> > > in Kconfig to only permit one of the two drivers to be configured.
> > >
> > > Ultimately we may need a better solution for the iio-hwmon bridge,
> > > one that makes the underlying driver transparent in both devicetree
> > > properties and user space ABI. No idea how to do that, though.
> >
> > IDK if ina2xx is a special case or if this matter of dual driver
> > stacks for the same chip already occurred and requires specific
> > plumbing. Making the user aware of the mutual of the exclusion sounds
> > fine with me.
> htu21. We'll drop that driver from hwmon with the 4.5 kernel.
> We could just drop ina2xx as well, but it is more widely used
> and referenced from dts files. The ABI changes, so I am not sure
> if we can just do that.

I changed iio/adc/Kconfig to the following:

+config INA2XX_ADC
+       tristate "Texas Instruments INA2xx Power Monitors IIO driver"
+       depends on I2C && !SENSORS_INA2XX
+       select REGMAP_I2C
+       select IIO_BUFFER
+       select IIO_KFIFO_BUF
+       help
+         Say yes here to build support for TI INA2xx family of Power 
Monitors.
+         This driver is mutually exclusive with the HWMON version.
+


anything the patch should also add to hwmon/Kconfig (that will not lead 
to a cycling reference warning) ?


> Guenter

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