linux-kernel - Re: [PATCH 3/3] iio: proximity: Add a ChromeOS EC MKBP proximity driver

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Message-ID: <161160076017.76967.4467861058817044169@swboyd.mtv.corp.google.com>
Date:   Mon, 25 Jan 2021 10:52:40 -0800
From:   Stephen Boyd <swboyd@...omium.org>
To:     Gwendal Grignou <gwendal@...omium.org>,
        Jonathan Cameron <jic23@...nel.org>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        linux-iio <linux-iio@...r.kernel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Benson Leung <bleung@...omium.org>,
        Guenter Roeck <groeck@...omium.org>,
        Douglas Anderson <dianders@...omium.org>
Subject: Re: [PATCH 3/3] iio: proximity: Add a ChromeOS EC MKBP proximity driver

Quoting Gwendal Grignou (2021-01-24 13:41:44)
> On Sun, Jan 24, 2021 at 9:38 AM Jonathan Cameron <jic23@...nel.org> wrote:
> >
> > On Fri, 22 Jan 2021 14:54:43 -0800
> > Stephen Boyd <swboyd@...omium.org> wrote:
> >
> > > ---
> > >  drivers/iio/proximity/Kconfig             |  11 +
> > >  drivers/iio/proximity/Makefile            |   1 +
> > >  drivers/iio/proximity/cros_ec_proximity.c | 252 ++++++++++++++++++++++

I suppose I'll change this to cros_ec_mkbp_proximity as well.

> > > diff --git a/drivers/iio/proximity/cros_ec_proximity.c b/drivers/iio/proximity/cros_ec_proximity.c
> > > new file mode 100644
> > > index 000000000000..a3aef911e3cc
> > > --- /dev/null
> > > +++ b/drivers/iio/proximity/cros_ec_proximity.c
> > > @@ -0,0 +1,252 @@
[...]
> > > +
> > > +static int cros_ec_proximity_query(struct cros_ec_device *ec_dev, int *state)
> > > +{
> > > +     struct ec_params_mkbp_info *params;
> > > +     struct cros_ec_command *msg;
> > > +     int ret;
> > > +
> > > +     msg = kzalloc(sizeof(*msg) + max(sizeof(u32), sizeof(*params)),
> > > +                   GFP_KERNEL);
> >
> > Given this is known at build time, perhaps better to add it to the
> > iio_priv() accessed structure and avoid having to handle allocations
> > separately.
> As Jonathan said, it can be preallocated in iio private structure. We
> can also use the stack, given the response size is known beforehand.
> See cros_ec_cec_set_log_addr() or cros_ec_pwm_get_duty() for example.

I suppose stack is even simpler. I'll try that.

> > > +
> > > +static int cros_ec_proximity_notify(struct notifier_block *nb,
> > > +                          unsigned long queued_during_suspend, void *_ec)
> > > +{
> > > +     struct cros_ec_proximity_data *data;
> > > +     struct cros_ec_device *ec = _ec;
> > > +     u8 event_type = ec->event_data.event_type & EC_MKBP_EVENT_TYPE_MASK;
> > > +     void *switches = &ec->event_data.data.switches;
> > > +     struct iio_dev *indio_dev;
> > > +     s64 timestamp;
> > > +     int state, dir;
> > > +     u64 ev;
> > > +
> > > +     if (event_type == EC_MKBP_EVENT_SWITCH) {
> > > +             data = container_of(nb, struct cros_ec_proximity_data, notifier);
> > > +             indio_dev = data->indio_dev;
> > > +
> > > +             mutex_lock(&data->lock);
> > > +             if (data->enabled) {
> > > +                     timestamp = iio_get_time_ns(indio_dev);
> For Android, given the timestamp must be time it happens, not reported
> [https://source.android.com/devices/sensors/sensors-hal2] """The
> timestamp must be accurate and correspond to the time at which the
> event physically happened, not the time it was reported.""", consider
> using ec_dev->last_event_time and apply a delta if the iio clock base
> is different from CLOCK_BOOTTIME.

Ah alright. Is there a reason why cros_ec_get_time_ns() is using
boottime instead of plain ktime_get(), i.e. CLOCK_MONOTONIC? Otherwise I
suppose some sort of cros_ec API should be exposed to convert the
last_event_time to whatever clock base is desired. Does that exist?

> > > +static int cros_ec_proximity_probe(struct platform_device *pdev)
> > > +{
> > > +     struct device *dev = &pdev->dev;
> > > +     struct cros_ec_device *ec = dev_get_drvdata(dev->parent);
> > > +     struct iio_dev *indio_dev;
> > > +     struct cros_ec_proximity_data *data;
> > > +     int ret;
> > > +
> > > +     indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
> > > +     if (!indio_dev)
> > > +             return -ENOMEM;
> > > +
> > > +     data = iio_priv(indio_dev);
> > > +     data->ec = ec;
> > > +     data->indio_dev = indio_dev;
> > > +     mutex_init(&data->lock);
> > > +     platform_set_drvdata(pdev, data);
> > > +
> > > +     indio_dev->name = "cros_ec_proximity";
> Define a constant CROS_EC_[MKBP_]PROXIMITY_DRIVER_NAME and use it here
> and in struct platform_driver cros_ec_proximity_driver.

I used dev->driver->name instead. Yay for no define!

> > > +     indio_dev->dev.parent = dev;
> Not needed, done by iio_device_alloc(), called by devm_iio_device_alloc().

Ok.

> > > +static const struct of_device_id cros_ec_proximity_of_match[] = {
> > > +     { .compatible = "google,cros-ec-proximity" },
> > > +     {}
> > > +};
> > > +MODULE_DEVICE_TABLE(of, cros_ec_proximity_of_match);
> > > +#endif
> > > +
> > > +static struct platform_driver cros_ec_proximity_driver = {
> > > +     .driver = {
> > > +             .name = "cros-ec-proximity",
> > > +             .of_match_table = of_match_ptr(cros_ec_proximity_of_match),
> Add a ACPI match table to match.

I don't have an ACPI system in hand. What should the ACPI table look
like? Can ACPI use the of_match_table logic?

> > > +     },
> > > +     .probe = cros_ec_proximity_probe,
> > > +     .remove = cros_ec_proximity_remove,
> > > +};