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Date: Mon, 1 Feb 2021 14:36:25 +0000
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Cristian Marussi <cristian.marussi@....com>
CC: Jonathan Cameron <jic23@...nel.org>,
Jyoti Bhayana <jbhayana@...gle.com>,
Hartmut Knaack <knaack.h@....de>,
Lars-Peter Clausen <lars@...afoo.de>,
"Peter Meerwald-Stadler" <pmeerw@...erw.net>,
Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
"David S. Miller" <davem@...emloft.net>,
"Rob Herring" <robh@...nel.org>,
Lukas Bulwahn <lukas.bulwahn@...il.com>,
<linux-kernel@...r.kernel.org>, <linux-iio@...r.kernel.org>,
<sudeep.holla@....com>, <egranata@...gle.com>,
<mikhail.golubev@...nsynergy.com>, <Igor.Skalkin@...nsynergy.com>,
<Peter.hilber@...nsynergy.com>, <ankitarora@...gle.com>
Subject: Re: [RFC PATCH v4 1/1] iio/scmi: Adding support for IIO SCMI Based
Sensors
On Sun, 31 Jan 2021 20:42:20 +0000
Cristian Marussi <cristian.marussi@....com> wrote:
> Hi
>
> a clarification down below regarding something I pointed out in the
> other thread (just to be sure I have not pointed out something
> plain wrong :D)
>
> Thanks
>
> Cristian
>
> On Sun, Jan 31, 2021 at 01:11:41PM +0000, Jonathan Cameron wrote:
> > On Fri, 29 Jan 2021 22:18:18 +0000
> > Jyoti Bhayana <jbhayana@...gle.com> wrote:
> >
> > > This change provides ARM SCMI Protocol based IIO device.
> > > This driver provides support for Accelerometer and Gyroscope using
> > > SCMI Sensor Protocol extensions added in the SCMIv3.0 ARM specification
> > >
> > > Signed-off-by: Jyoti Bhayana <jbhayana@...gle.com>
> >
> > A few minor things noticed on a fresh read through, but mostly I think
> > we are down to figuring out how to deal with the range (as discussed
> > in the thread continuing on v3).
> >
> > On another note, probably time to drop the RFC or give a bit more detail
> > on why you think this isn't ready to be applied.
> >
> > Thanks,
> >
> > Jonathan
> >
> [snip]
>
> > > +
> > > +static int scmi_iio_dev_probe(struct scmi_device *sdev)
> > > +{
> > > + const struct scmi_sensor_info *sensor_info;
> > > + struct scmi_handle *handle = sdev->handle;
> > > + struct device *dev = &sdev->dev;
> > > + struct iio_dev *scmi_iio_dev;
> > > + u16 nr_sensors;
> > > + int err, i;
> > > +
> > > + if (!handle || !handle->sensor_ops) {
> > > + dev_err(dev, "SCMI device has no sensor interface\n");
> > I'm going to guess we can't actually get here because the registration
> > would't have happened if either of those are true?
> > If so perhaps drop the error message.
> >
> > > + return -EINVAL;
> > > + }
> > > +
> > > + nr_sensors = handle->sensor_ops->count_get(handle);
> > > + if (!nr_sensors) {
> > > + dev_dbg(dev, "0 sensors found via SCMI bus\n");
> > -ENODEV maybe?
> > > + return -EINVAL;
> > > + }
> > > +
> > > + dev_dbg(dev, "%d sensors found via SCMI bus\n", nr_sensors);
> >
> > Clear out any debug prints out that don't provide info that can't be obtained
> > farily easily from elsewhere. In this case they will either be registered
> > or not and we'll get error messages.
> > These sort of prints bitrot over time so we want to limit them to the truely
> > useful.
> >
> > > +
> > > + for (i = 0; i < nr_sensors; i++) {
> > > + sensor_info = handle->sensor_ops->info_get(handle, i);
> > > + if (!sensor_info) {
> > > + dev_err(dev, "SCMI sensor %d has missing info\n", i);
> > > + return -EINVAL;
> > > + }
> > > +
> > > + /* Skipping scalar sensor,as this driver only supports accel and gyro */
> > > + if (sensor_info->num_axis == 0)
> > > + continue;
> >
> > So there is a situation where this driver never creates anything? In that path I'd
> > like to see an -ENODEV error return.
> >
> You mean -ENODEV only if this driver does not find at least one
> good/supported GYRO/ACCEL sensor right ?
Exactly.
>
> I would expect a system to possibly expose a bunch of other SCMI sensors
> maybe unsupported by this IIO driver but currently handled by other
> drivers, as an example on JUNO a number of temps/volts/currents sensors
> are exposed and handled by the SCMI hwmon driver.
>
>
> > > +
> > > + err = scmi_alloc_iiodev(dev, handle, sensor_info,
> > > + &scmi_iio_dev);
> > > + if (err < 0) {
> > > + dev_err(dev,
> > > + "failed to allocate IIO device for sensor %s: %d\n",
> > > + sensor_info->name, err);
> > > + return err;
> > > + }
> > > +
> > > + err = scmi_iio_buffers_setup(scmi_iio_dev);
> > > + if (err < 0) {
> > > + dev_err(dev,
> > > + "IIO buffer setup error at sensor %s: %d\n",
> > > + sensor_info->name, err);
> > > + return err;
> > > + }
> > > +
> > > + err = devm_iio_device_register(dev, scmi_iio_dev);
> > > + if (err) {
> > > + dev_err(dev,
> > > + "IIO device registration failed at sensor %s: %d\n",
> > > + sensor_info->name, err);
> > > + return err;
> > > + }
> > > + }
> > > + return err;
> > > +}
> > > +
> > > +static const struct scmi_device_id scmi_id_table[] = {
> > > + { SCMI_PROTOCOL_SENSOR, "iiodev" },
> >
> > I'm curious on this. What actually causes a match on that
> > iiodev? From digging around the scmi core am I right in thinking
> > that this iiodev id needs to be explicitly listed?
> >
> > It would be good to include any changes needed there in this
> > series.
> >
> > > + {},
> > > +};
> > > +
> > > +MODULE_DEVICE_TABLE(scmi, scmi_id_table);
> > > +
> > > +static struct scmi_driver scmi_iiodev_driver = {
> > > + .name = "scmi-sensor-iiodev",
> > > + .probe = scmi_iio_dev_probe,
> > > + .id_table = scmi_id_table,
> > > +};
> > > +
> > > +module_scmi_driver(scmi_iiodev_driver);
> > > +
> > > +MODULE_AUTHOR("Jyoti Bhayana <jbhayana@...gle.com>");
> > > +MODULE_DESCRIPTION("SCMI IIO Driver");
> > > +MODULE_LICENSE("GPL v2");
> >
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