Re: [PATCH v2] iio: cros: Register FIFO callback after sensor is registered

[Doug Anderson <dianders@chromium.org>]

Hi,

On Sat, Jun 25, 2022 at 3:24 PM Gwendal Grignou <gwendal@chromium.org> wrote:
>
> Instead of registering callback to process sensor events right at
> initialization time, wait for the sensor to be register in the iio
> subsystem.
>
> Events can come at probe time (in case the kernel rebooted abruptly
> without switching the sensor off for  instance), and be sent to IIO core
> before the sensor is fully registered.
>
> Reported-by: Douglas Anderson <dianders@chromium.org>
> Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
> ---
> Changes since v1:
> - renamed from "iio: cros: Add cros_ec_sensors_core_register"
> - Call devm_iio_device_register() inside cros_ec_sensors_core_register.
>
>  drivers/iio/accel/cros_ec_accel_legacy.c      |  4 +-
>  .../cros_ec_sensors/cros_ec_lid_angle.c       |  4 +-
>  .../common/cros_ec_sensors/cros_ec_sensors.c  |  6 +-
>  .../cros_ec_sensors/cros_ec_sensors_core.c    | 58 ++++++++++++++-----
>  drivers/iio/light/cros_ec_light_prox.c        |  6 +-
>  drivers/iio/pressure/cros_ec_baro.c           |  6 +-
>  .../linux/iio/common/cros_ec_sensors_core.h   |  7 ++-
>  7 files changed, 60 insertions(+), 31 deletions(-)
>
> diff --git a/drivers/iio/accel/cros_ec_accel_legacy.c b/drivers/iio/accel/cros_ec_accel_legacy.c
> index 1c0171f26e99e..0f403342b1fc0 100644
> --- a/drivers/iio/accel/cros_ec_accel_legacy.c
> +++ b/drivers/iio/accel/cros_ec_accel_legacy.c
> @@ -215,7 +215,7 @@ static int cros_ec_accel_legacy_probe(struct platform_device *pdev)
>                 return -ENOMEM;
>
>         ret = cros_ec_sensors_core_init(pdev, indio_dev, true,
> -                                       cros_ec_sensors_capture, NULL);
> +                                       cros_ec_sensors_capture);
>         if (ret)
>                 return ret;
>
> @@ -235,7 +235,7 @@ static int cros_ec_accel_legacy_probe(struct platform_device *pdev)
>                 state->sign[CROS_EC_SENSOR_Z] = -1;
>         }
>
> -       return devm_iio_device_register(dev, indio_dev);
> +       return cros_ec_sensors_core_register(dev, indio_dev, NULL);

In the case where the last argument is NULL then the new
cros_ec_sensors_core_register() is always equivalent to the old
devm_iio_device_register(), right? ...but I guess it's more idiomatic
to always use the cros_ec version, so I'm OK with this.


> @@ -372,6 +358,46 @@ int cros_ec_sensors_core_init(struct platform_device *pdev,
>  }
>  EXPORT_SYMBOL_GPL(cros_ec_sensors_core_init);
>
> +/**
> + * cros_ec_sensors_core_register() - Register callback to FIFO and IIO when
> + * sensor is ready.
> + * It must be called at the end of the sensor probe routine.
> + * @dev:               device created for the sensor
> + * @indio_dev:         iio device structure of the device
> + * @push_data:          function to call when cros_ec_sensorhub receives
> + *    a sample for that sensor.
> + *
> + * Return: 0 on success, -errno on failure.
> + */
> +int cros_ec_sensors_core_register(struct device *dev,
> +                                 struct iio_dev *indio_dev,
> +                                 cros_ec_sensorhub_push_data_cb_t push_data)
> +{
> +       struct cros_ec_sensor_platform *sensor_platform = dev_get_platdata(dev);
> +       struct cros_ec_sensorhub *sensor_hub = dev_get_drvdata(dev->parent);
> +       struct platform_device *pdev = to_platform_device(dev);
> +       struct cros_ec_dev *ec = sensor_hub->ec;
> +       int ret = 0;

nit: don't init "ret" to 0 when you simply assign it right below.


> +       ret = devm_iio_device_register(dev, indio_dev);
> +       if (ret)
> +               return ret;
> +
> +       if (cros_ec_check_features(ec, EC_FEATURE_MOTION_SENSE_FIFO) &&
> +           push_data != NULL) {

I think the check for push_data should be first so it can short
circuit and avoid the call to cros_ec_check_features(), right?

In the past I've been yelled at for using "!= NULL" and told that
thing should simply be "&& push_data". I'll leave it up to you about
whether it's something that should be changed here.

Also: you can reduce indentation of the function and simply if you just do:

if (!push_data || !cros_ec_check_features(...))
  return 0;

-Doug