linux-kernel - Re: [PATCH v3 4/9] iio: accel: bma400: Add triggered buffer support

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Date:   Tue, 12 Apr 2022 12:12:21 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Jagath Jog J <jagathjog1996@...il.com>
Cc:     Dan Robertson <dan@...obertson.com>,
        Jonathan Cameron <jic23@...nel.org>,
        linux-iio <linux-iio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 4/9] iio: accel: bma400: Add triggered buffer support

On Mon, Apr 11, 2022 at 11:31 PM Jagath Jog J <jagathjog1996@...il.com> wrote:
>
> Added trigger buffer support to read continuous acceleration
> data from device with data ready interrupt which is mapped
> to INT1 pin.

Can you explain the locking schema in this driver?

> +       /* Configure INT1 pin to open drain */
> +       ret = regmap_write(data->regmap, BMA400_INT_IO_CTRL_REG, 0x06);
> +       if (ret)
> +               return ret;

No locking (or regmap only locking).

...

> +static int bma400_data_rdy_trigger_set_state(struct iio_trigger *trig,
> +                                            bool state)
> +{
> +       struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
> +       struct bma400_data *data = iio_priv(indio_dev);
> +       int ret;
> +
> +       ret = regmap_update_bits(data->regmap, BMA400_INT_CONFIG0_REG,
> +                                BMA400_INT_DRDY_MSK,
> +                                FIELD_PREP(BMA400_INT_DRDY_MSK, state));
> +       if (ret)
> +               return ret;
> +
> +       return regmap_update_bits(data->regmap, BMA400_INT1_MAP_REG,
> +                                 BMA400_INT_DRDY_MSK,
> +                                 FIELD_PREP(BMA400_INT_DRDY_MSK, state));
> +}

Ditto.

...

> +       mutex_lock(&data->mutex);
> +
> +       /* bulk read six registers, with the base being the LSB register */
> +       ret = regmap_bulk_read(data->regmap, BMA400_X_AXIS_LSB_REG,
> +                              &data->buffer.buff, sizeof(data->buffer.buff));
> +       mutex_unlock(&data->mutex);
> +       if (ret)
> +               return IRQ_NONE;

But here only above with locking...

> +       ret = regmap_read(data->regmap, BMA400_TEMP_DATA_REG, &temp);
> +       if (ret)
> +               return IRQ_NONE;

...followed by no locking.

...

> +       mutex_lock(&data->mutex);
> +       ret = regmap_bulk_read(data->regmap, BMA400_INT_STAT0_REG, &status,
> +                              sizeof(status));
> +       mutex_unlock(&data->mutex);
> +       if (ret)
> +               return IRQ_NONE;

And again with locking.

...

So,
1) Does regmap is configured with locking? What for?
2) What's the role of data->mutex?

-- 
With Best Regards,
Andy Shevchenko