mpm: sys_utils: add libgpiod-based Gpio helper

This adds a new Gpio helper class, which uses libgpiod under the
hood instead of the deprecated sysfs GPIO access. This class provides
the ability to get/set a specific GPIO, which is looked up by name.

1 files changed, 60 insertions, 0 deletions

diff --git a/mpm/python/usrp_mpm/sys_utils/gpio.py b/mpm/python/usrp_mpm/sys_utils/gpio.py
new file mode 100644
index 000000000..b609479f1
--- /dev/null
+++ b/mpm/python/usrp_mpm/sys_utils/gpio.py
@@ -0,0 +1,60 @@
+#
+# Copyright 2020 Ettus Research, a National Instruments Brand
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+"""
+Access to GPIOs via libgpiod
+"""
+
+import contextlib
+import gpiod
+
+
+@contextlib.contextmanager
+def request_gpio(line, direction):
+    """
+    Context manager for a GPIO line
+    """
+    line.request(consumer='mpm', type=direction)
+    try:
+        yield line
+    finally:
+        line.release()
+
+
+class Gpio:
+    """
+    Class for accessing a named GPIO line via libgpiod
+    """
+
+    INPUT = gpiod.LINE_REQ_DIR_IN
+    OUTPUT = gpiod.LINE_REQ_DIR_OUT
+
+    def __init__(self, name, direction=INPUT, default_val=None):
+        self._direction = direction
+        self._line = gpiod.find_line(name)
+        self._out_value = False
+        if self._line is None:
+            raise RuntimeError('failed to find gpio with name %s' % name)
+
+        if default_val is not None and direction == Gpio.OUTPUT:
+            self.set(default_val)
+
+    def get(self):
+        """
+        Read the value of this GPIO
+        """
+        if self._direction == self.OUTPUT:
+            return self._out_value
+
+        with request_gpio(self._line, self._direction) as gpio:
+            return bool(gpio.get_value())
+
+    def set(self, value):
+        """
+        Set the value of this GPIO
+        """
+        with request_gpio(self._line, self._direction) as gpio:
+            gpio.set_value(int(value))
+            self._out_value = bool(value)