Re: [PATCH v3 0/1] iio/scmi: Add reading "raw" attribute.

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Hi, Jyoti,

In the code below, why is the logic of enabling and disabling the
sensor in this function?  Generally the function to read the sensor
value is just used for the code to read the sensor values ? and not
enable/disable the sensor

But to read sensor value we have to enable it first. Other way to enable sensor we found is, for example:

  echo 1 > /sys/bus/iio/devices/.../scan_elements/in_anglvel_x_en

But, this command is related to IIO buffers use.

Other sensors drivers enable/disable sensor in read raw too, for example, drivers/iio/accel/kxcjk-1013.c has:

  case IIO_CHAN_INFO_RAW:
          mutex_lock(&data->mutex);
          if (iio_buffer_enabled(indio_dev))
                  ret = -EBUSY;
          else {
                  ret = kxcjk1013_set_power_state(data, true);
                  ... reading ...
                  ret = kxcjk1013_set_power_state(data, false);
          }
          mutex_unlock(&data->mutex);

But, after looking on this code I have some questions:

1. Should we block reading raw attribute and IIO buffer enabled, for for SCMI sensor it can coexist? 2. Should we wrap reading raw attribute implementation in iio_dev->mlock mutex?

    case IIO_CHAN_INFO_RAW:
+               sensor_config = FIELD_PREP(SCMI_SENS_CFG_SENSOR_ENABLED_MASK,
+                                          SCMI_SENS_CFG_SENSOR_ENABLE);
+               err = sensor->sensor_ops->config_set(
+                       sensor->ph, sensor->sensor_info->id, sensor_config);
+               if (err) {
+                       dev_err(&iio_dev->dev,
+                               "Error in enabling sensor %s err %d",
+                               sensor->sensor_info->name, err);
+                       return err;
+               }
+
+               err = sensor->sensor_ops->reading_get_timestamped(
+                       sensor->ph, sensor->sensor_info->id,
+                       sensor->sensor_info->num_axis, readings);
+               if (err) {
+                       dev_err(&iio_dev->dev,
+                               "Error in reading raw attribute for sensor %s err %d",
+                               sensor->sensor_info->name, err);
+                       return err;
+               }
+
+               sensor_config = FIELD_PREP(SCMI_SENS_CFG_SENSOR_ENABLED_MASK,
+                                          SCMI_SENS_CFG_SENSOR_DISABLE);
+               err = sensor->sensor_ops->config_set(
+                       sensor->ph, sensor->sensor_info->id, sensor_config);
+               if (err) {
+                       dev_err(&iio_dev->dev,
+                               "Error in enabling sensor %s err %d",
+                               sensor->sensor_info->name, err);
+                       return err;
+               }
+               /* Check if raw value fits 32 bits */
+               if (readings[ch->scan_index].value < INT_MIN ||
+                   readings[ch->scan_index].value > INT_MAX)
+                       return -ERANGE;
+               /* Use 32-bit value, since practically there is no need in 64 bits */
+               *val = (int)readings[ch->scan_index].value;

+               return IIO_VAL_INT;



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