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

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On 3/23/23 05:01, Naresh Solanki wrote:
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);

dev_name() in general should not be used for indio_dev->name, it does not meet the ABI requirements for the IIO ABI. Move this into the switch block below and then assign "max5970" or "max5978" depending on the device type.





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