X-Git-Url: https://git.ayoreis.com/Adafruit_Blinka-hackapet.git/blobdiff_plain/de652f72b1884328ee22ec36deaa6320addd32e7..d556ebd4688addd339a237a9cb8d5960823f18f3:/src/adafruit_blinka/microcontroller/generic_linux/sysfs_pwmout.py

diff --git a/src/adafruit_blinka/microcontroller/generic_linux/sysfs_pwmout.py b/src/adafruit_blinka/microcontroller/generic_linux/sysfs_pwmout.py
index 4fc8e23..9bf2602 100644
--- a/src/adafruit_blinka/microcontroller/generic_linux/sysfs_pwmout.py
+++ b/src/adafruit_blinka/microcontroller/generic_linux/sysfs_pwmout.py
@@ -1,3 +1,6 @@
+# SPDX-FileCopyrightText: 2021 Melissa LeBlanc-Williams for Adafruit Industries
+#
+# SPDX-License-Identifier: MIT
 """
 Much code from https://github.com/vsergeev/python-periphery/blob/master/periphery/pwm.py
 Copyright (c) 2015-2016 vsergeev / Ivan (Vanya) A. Sergeev
@@ -5,6 +8,8 @@ License: MIT
 """
 
 import os
+from time import sleep
+from errno import EACCES
 
 try:
     from microcontroller.pin import pwmOuts
@@ -25,6 +30,11 @@ class PWMError(IOError):
 class PWMOut:
     """Pulse Width Modulation Output Class"""
 
+    # Number of retries to check for successful PWM export on open
+    PWM_STAT_RETRIES = 10
+    # Delay between check for scucessful PWM export on open (100ms)
+    PWM_STAT_DELAY = 0.1
+
     # Sysfs paths
     _sysfs_path = "/sys/class/pwm/"
     _channel_path = "pwmchip{}"
@@ -98,17 +108,39 @@ class PWMOut:
 
         try:
             with open(
-                os.path.join(channel_path, self._unexport_path), "w"
+                os.path.join(channel_path, self._unexport_path), "w", encoding="utf-8"
             ) as f_unexport:
                 f_unexport.write("%d\n" % self._pwmpin)
-        except IOError as e:
+        except IOError:
             pass  # not unusual, it doesnt already exist
         try:
-            with open(os.path.join(channel_path, self._export_path), "w") as f_export:
+            with open(
+                os.path.join(channel_path, self._export_path), "w", encoding="utf-8"
+            ) as f_export:
                 f_export.write("%d\n" % self._pwmpin)
         except IOError as e:
             raise PWMError(e.errno, "Exporting PWM pin: " + e.strerror) from IOError
 
+        # Loop until 'period' is writable, because application of udev rules
+        # after the above pin export is asynchronous.
+        # Without this loop, the following properties may not be writable yet.
+        for i in range(PWMOut.PWM_STAT_RETRIES):
+            try:
+                with open(
+                    os.path.join(
+                        channel_path, self._pin_path.format(self._pwmpin), "period"
+                    ),
+                    "w",
+                    encoding="utf-8",
+                ):
+                    break
+            except IOError as e:
+                if e.errno != EACCES or (
+                    e.errno == EACCES and i == PWMOut.PWM_STAT_RETRIES - 1
+                ):
+                    raise PWMError(e.errno, "Opening PWM period: " + e.strerror) from e
+            sleep(PWMOut.PWM_STAT_DELAY)
+
         # self._set_enabled(False) # This line causes a write error when trying to enable
 
         # Look up the period, for fast duty cycle updates
@@ -126,13 +158,14 @@ class PWMOut:
     def deinit(self):
         """Deinit the sysfs PWM."""
         if self._channel is not None:
-            self.duty_cycle = 0
             try:
                 channel_path = os.path.join(
                     self._sysfs_path, self._channel_path.format(self._channel)
                 )
                 with open(
-                    os.path.join(channel_path, self._unexport_path), "w"
+                    os.path.join(channel_path, self._unexport_path),
+                    "w",
+                    encoding="utf-8",
                 ) as f_unexport:
                     f_unexport.write("%d\n" % self._pwmpin)
             except IOError as e:
@@ -161,7 +194,7 @@ class PWMOut:
             attr,
         )
 
-        with open(path, "w") as f_attr:
+        with open(path, "w", encoding="utf-8") as f_attr:
             # print(value, path)
             f_attr.write(value + "\n")
 
@@ -176,7 +209,7 @@ class PWMOut:
             attr,
         )
 
-        with open(path, "r") as f_attr:
+        with open(path, "r", encoding="utf-8") as f_attr:
             return f_attr.read().strip()
 
     # Mutable properties