Re: [PATCH 1/2] iio: max597x: Add support for max597x

[Naresh Solanki <naresh.solanki@xxxxxxxxxxxxx>]

Hi,

On 22-03-2023 09:28 pm, Lars-Peter Clausen wrote:
> Hi,
>
> This looks really good. A few minor comments inline.
>
> On 3/22/23 05:43, Naresh Solanki wrote:
> > [...]
> > +static int max597x_iio_read_raw(struct iio_dev *iio_dev,
> > +                struct iio_chan_spec const *chan,
> > +                int *val, int *val2, long info)
> > +{
> > +    int ret;
> > +    struct max597x_iio *data = iio_priv(iio_dev);
> > +    unsigned int reg_l, reg_h;
> > +
> > +    switch (info) {
> > +    case IIO_CHAN_INFO_RAW:
> > +        ret = regmap_read(data->regmap, chan->address, &reg_l);
> > +        if (ret < 0)
> > +            return ret;
> > +        ret = regmap_read(data->regmap, chan->address - 1, &reg_h);
> > +        if (ret < 0)
> > +            return ret;
> Is there any chance of a race condition of getting inconsistent data 
> when splitting this over two reads? I.e. registers being updated with 
> new values in between the two reads.
yes, reg_l holds lower 2 bits. due to latency in reads, value may differ.
> > +        *val = (reg_h << 2) | (reg_l & 3);
> > +
> > +        return IIO_VAL_INT;
> > +    case IIO_CHAN_INFO_SCALE:
> > +
> > +        switch (chan->address) {
> > +        case MAX5970_REG_CURRENT_L(0):
> > +            fallthrough;
>
> `fallthrough` should not be needed for multiple case statements right on 
> top of each other with no code in between. Same below
Sure.
> > +        case MAX5970_REG_CURRENT_L(1):
> > +            /* in A, convert to mA */
> > +            *val = data->irng[chan->channel] * 1000;
> > +            *val2 =
> > +                data->shunt_micro_ohms[chan->channel] * ADC_MASK;
> ADC_MASK should really have a MAX5970_ prefix, but I guess it is defined 
> in max597x.h
Yes its taken from max597x.h
> > +            return IIO_VAL_FRACTIONAL;
> > +
> > +        case MAX5970_REG_VOLTAGE_L(0):
> > +            fallthrough;
> > +        case MAX5970_REG_VOLTAGE_L(1):
> > +            /* in uV, convert to mV */
> > +            *val = data->mon_rng[chan->channel];
> > +            *val2 = ADC_MASK * 1000;
> > +            return IIO_VAL_FRACTIONAL;
> > +        }
> > +
> > +        break;
> > +    }
> > +    return -EINVAL;
> > +}
> > [..]
> > +static int max597x_iio_probe(struct platform_device *pdev)
> > +{
> > +    struct max597x_data *max597x = dev_get_drvdata(pdev->dev.parent);
> > +    struct i2c_client *i2c = to_i2c_client(pdev->dev.parent);
> > +    struct regmap *regmap = dev_get_regmap(pdev->dev.parent, NULL);
> > +    struct iio_dev *indio_dev;
> > +    struct max597x_iio *priv;
> > +    int ret, i;
> > +
> > +    if (!regmap)
> > +        return -EPROBE_DEFER;
> > +
> > +    if (!max597x || !max597x->num_switches)
> > +        return -EPROBE_DEFER;
> > +
> > +    /* registering iio */
> > +    indio_dev = devm_iio_device_alloc(&i2c->dev, sizeof(*priv));
> For the devm allocations we should be using &pdev->dev and not the I2C 
> device, since this is the device to which the allocations belong and 
> where they should be freed when the device is removed.
Sure. Will use &pdev->dev
> > +    if (!indio_dev) {
> > +        dev_err(&i2c->dev, "failed allocating iio device\n");
> Consider using dev_err_probe() for error message printing. This will 
> give a consistent formatting of the messages. Also again use &pdev->dev 
> instead of I2C device to get the right device listed in the error messages.
Sure. Will use
dev_err_probe(&pdev->dev, ret, "could not register iio device");
> > +        return -ENOMEM;
> > +    }
> > +    indio_dev->name = dev_name(&i2c->dev);
> The IIO ABI wants the type of the chip for the name. E.g. "max5970", 
> using dev_name() of the parent I2C device will result in something else.
Sure. Will make it:
indio_dev->name = dev_name(&pdev->dev);
> > [...]

Regards,
Naresh