adi: ad4020: Add reset_buffer convenience decorator

Functions that need to write to the device may fail if there is an active
(enabled) IIO buffer at the moment. That's because the same physical SPI
lines cannot both provide data to the host controller and receive
configuration at the same time. Driver developers (and the Linux IIO
subsystem) prevent such concurrent access by locking a mutex and not
allowing buffered readings until configuration transfers end. Conversely,
attempts to do direct transfers while a buffer is enabled return -EBUSY.
Decorate functions that do direct device access to reset (and disable)
the read buffer, thus allowing the device configuration to happen.

Signed-off-by: Marcelo Schmitt <[email protected]>

adi/ad4020.py

@@ -10,6 +10,19 @@
 from adi.rx_tx import rx
 
 
+def reset_buffer(func):
+    """Wrapper for set calls that require device configuration.
+    Without disabling the buffer, direct access will return -EBUSY
+    """
+
+    def wrapper(*args, **kwargs):
+        if args[0]._reset_on_spi_writes:
+            args[0].rx_destroy_buffer()
+        func(*args, **kwargs)
+
+    return wrapper
+
+
 class ad4020(rx, context_manager):
     """AD4000 series of differential SAR ADC device"""
 
@@ -23,6 +36,7 @@ class ad4020(rx, context_manager):
     _rx_data_type = np.int32
     _complex_data = False
     _rx_channel_names = ["voltage0"]
+    _reset_on_spi_writes = True
 
     def __init__(self, uri="", device_name="ad4020"):
         if not device_name:
@@ -51,13 +65,16 @@ def sampling_frequency(self):
         return self._get_iio_dev_attr("sampling_frequency")
 
     @sampling_frequency.setter
+    @reset_buffer
     def sampling_frequency(self, value):
         """Set the sampling frequency."""
         self._set_iio_dev_attr("sampling_frequency", str(value))
 
     class _channel_adc(attribute):
         """AD4000 series differential input voltage channel"""
 
+        _reset_on_spi_writes = True
+
         # AD4000 series ADC channel
         def __init__(self, ctrl, channel_name, output):
             self.name = channel_name
@@ -73,6 +90,7 @@ def scale(self):
             return float(self._get_iio_attr_str(self.name, "scale", self._output))
 
         @scale.setter
+        @reset_buffer
         def scale(self, value):
             self._set_iio_attr(self.name, "scale", False, str(Decimal(value).real))