Add timout loop after exporting the PWM pin.

This gives udev time to respond to the device event. Without this,
the subsequent attempts to modify pin properties will fail when
depending on udev rules to apply new user permissions.

This code is essentially copied from python-periphery, as was most
of this file (both MIT licenced). Although it appears sergeev added
this loop recently, compared to when this code was originally cloned.

diff --git a/src/adafruit_blinka/microcontroller/generic_linux/sysfs_pwmout.py b/src/adafruit_blinka/microcontroller/generic_linux/sysfs_pwmout.py
index e95a1e627c74c4d1ea4e7f10a4343fe5b450821e..ae4da4b78124eefbd15b5b35723efc984ac5f0bf 100644 (file)
--- a/src/adafruit_blinka/microcontroller/generic_linux/sysfs_pwmout.py
+++ b/src/adafruit_blinka/microcontroller/generic_linux/sysfs_pwmout.py
@@ -31,6 +31,11 @@ class PWMOut:
     # 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{}"
@@ -121,13 +126,16 @@ class PWMOut:
         for i in range(PWMOut.PWM_STAT_RETRIES):
             try:
                 with open(
-                    os.path.join(channel_path, self._pin_path.format(self._pwmpin), "period"), 'w'
+                    os.path.join(
+                        channel_path, self._pin_path.format(self._pwmpin), "period"
+                    ),
+                    "w",
                 ):
-                    print('#### okay ####')
                     break
             except IOError as e:
-                if e.errno != EACCES or (e.errno == EACCES and i == PWMOut.PWM_STAT_RETRIES - 1):
-                    print('#### catch ####')
+                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)