Add timout loop after exporting the PWM pin.

[Adafruit_Blinka-hackapet.git] / 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 5f72e4fd40d9d7cd738a8cebe5c31c7651a8a056..1344f4faf9216ee6e16dedc347886e22f9b4fd22 100644 (file)
--- a/src/adafruit_blinka/microcontroller/generic_linux/sysfs_pwmout.py
+++ b/src/adafruit_blinka/microcontroller/generic_linux/sysfs_pwmout.py
@@ -5,11 +5,13 @@ License: MIT
 """
 
 import os
 """
 
 import os

+from time import sleep
+from errno import EACCES

 
 try:
     from microcontroller.pin import pwmOuts
 except ImportError:
 
 try:
     from microcontroller.pin import pwmOuts
 except ImportError:

-    raise RuntimeError("No PWM outputs defined for this board")
+    raise RuntimeError("No PWM outputs defined for this board") from ImportError

 
 
 # pylint: disable=unnecessary-pass
 
 
 # pylint: disable=unnecessary-pass


@@ -25,6 +27,21 @@ class PWMError(IOError):
 class PWMOut:
     """Pulse Width Modulation Output Class"""
 
 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
+
+    # 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
+
+    # 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{}"
     # Sysfs paths
     _sysfs_path = "/sys/class/pwm/"
     _channel_path = "pwmchip{}"


@@ -85,6 +102,9 @@ class PWMOut:
         if self._channel is None:
             raise RuntimeError("No PWM channel found for this Pin")
 
         if self._channel is None:
             raise RuntimeError("No PWM channel found for this Pin")
 

+        if variable_frequency:
+            print("Variable Frequency is not supported, continuing without it...")
+

         channel_path = os.path.join(
             self._sysfs_path, self._channel_path.format(self._channel)
         )
         channel_path = os.path.join(
             self._sysfs_path, self._channel_path.format(self._channel)
         )


@@ -93,7 +113,6 @@ class PWMOut:
                 "PWM channel does not exist, check that the required modules are loaded."
             )
 
                 "PWM channel does not exist, check that the required modules are loaded."
             )
 

-        pin_path = os.path.join(channel_path, self._pin_path.format(self._pwmpin))

         try:
             with open(
                 os.path.join(channel_path, self._unexport_path), "w"
         try:
             with open(
                 os.path.join(channel_path, self._unexport_path), "w"


@@ -105,7 +124,26 @@ class PWMOut:
             with open(os.path.join(channel_path, self._export_path), "w") as f_export:
                 f_export.write("%d\n" % self._pwmpin)
         except IOError as e:
             with open(os.path.join(channel_path, self._export_path), "w") as f_export:
                 f_export.write("%d\n" % self._pwmpin)
         except IOError as e:

-            raise PWMError(e.errno, "Exporting PWM pin: " + e.strerror)
+            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",
+                ):
+                    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)
+            sleep(PWMOut.PWM_STAT_DELAY)

 
         # self._set_enabled(False) # This line causes a write error when trying to enable
 
 
         # self._set_enabled(False) # This line causes a write error when trying to enable
 


@@ -134,7 +172,9 @@ class PWMOut:
                 ) as f_unexport:
                     f_unexport.write("%d\n" % self._pwmpin)
             except IOError as e:
                 ) as f_unexport:
                     f_unexport.write("%d\n" % self._pwmpin)
             except IOError as e:

-                raise PWMError(e.errno, "Unexporting PWM pin: " + e.strerror)
+                raise PWMError(
+                    e.errno, "Unexporting PWM pin: " + e.strerror
+                ) from IOError

 
         self._channel = None
         self._pwmpin = None
 
         self._channel = None
         self._pwmpin = None


@@ -182,7 +222,9 @@ class PWMOut:
         try:
             period_ns = int(period_ns)
         except ValueError:
         try:
             period_ns = int(period_ns)
         except ValueError:

-            raise PWMError(None, 'Unknown period value: "%s"' % period_ns)
+            raise PWMError(
+                None, 'Unknown period value: "%s"' % period_ns
+            ) from ValueError

 
         # Convert period from nanoseconds to seconds
         period = period_ns / 1e9
 
         # Convert period from nanoseconds to seconds
         period = period_ns / 1e9


@@ -220,7 +262,9 @@ class PWMOut:
         try:
             duty_cycle_ns = int(duty_cycle_ns)
         except ValueError:
         try:
             duty_cycle_ns = int(duty_cycle_ns)
         except ValueError:

-            raise PWMError(None, 'Unknown duty cycle value: "%s"' % duty_cycle_ns)
+            raise PWMError(
+                None, 'Unknown duty cycle value: "%s"' % duty_cycle_ns
+            ) from ValueError

 
         # Convert duty cycle from nanoseconds to seconds
         duty_cycle = duty_cycle_ns / 1e9
 
         # Convert duty cycle from nanoseconds to seconds
         duty_cycle = duty_cycle_ns / 1e9