View difference between Paste ID: 1UCnbVNT and z2p618S6

-##### common for all of these #####
+# These examples assume /dev/gpio contains symlinks for sysfs gpios.
 #
 # Example udev rule:
 #
-_gpio_dir = Path('/dev/gpio')
+#	SUBSYSTEM=="subsystem", KERNEL=="gpio", ACTION=="add", \
 #		RUN+="/bin/mkdir -p /dev/gpio"
 #
 #	SUBSYSTEM=="gpio", ACTION=="add", TEST=="value", ATTR{label}!="sysfs", \
-##### version 1
+#		RUN+="/bin/ln -sT '/sys/class/gpio/%k' /dev/gpio/%s{label}"
 #
 # save as e.g. /etc/udev/rules.d/gpio-symlinks.rules
-    return int( (_gpio_dir/name/'value').read_text() )
+# then "sudo update-initramfs -u" (unless you don't use initramfs) and reboot
 #
 #
-    (_gpio_dir/name/'value').write_text( str(value) )
+# This code is written to be simple and correct, not necessarily efficient.
 # Performance can probably be greatly improved by keeping a file descriptor
 # open for the 'value' attribute and using os.pread() and os.write().  This
 # would also be the first step towards supporting input change events.
 #
 # This also assumes that the direction (input/output) of gpios has already
 # been setup, e.g. in DT.  Attempting to set the value of an input will not
 # change it to output, it will simply fail.  For a slightly more elaborate
-##### version 2
+# version of 'variant 1' that includes changing the direction of gpios and
 # also has more comments and error checking, see https://pastebin.com/cVHktYPn
 
 
 ##### variant 1
-        self._value_path = _gpio_dir/name/'value'
+
 from pathlib import Path
 
 def gpio_get_value( name ):
     return int( Path('/dev/gpio', name, 'value').read_text() )
 
 def gpio_set_value( name, value ):
     Path('/dev/gpio', name, 'value').write_text( str(value) )
 
 print( gpio_get_value( 'my-input' ) )
 print( gpio_get_value( 'my-output' ) )
 gpio_set_value( 'my-output', 1 )
 
 
 
 ##### variant 2
 
-##### version 3
+
 
 class Gpio:
     def __init__( self, name ):
         self.name = name
-        self._value_path = _gpio_dir/name/'value'
+        self._value_path = Path( '/dev/gpio', name, 'value' )
 
     def get_value( self ):
         return int( self._value_path.read_text() )
 
     def set_value( self, value ):
         self._value_path.write_text( str( value ) )
 
 my_input = Gpio('my-input')
 my_output = Gpio('my-output')
 
 print( my_input.get_value() )
 print( my_output.get_value() )
 my_output.set_value( 1 )
 
 
 
 ##### variant 3
 
 from pathlib import Path
 
 class Gpio:
     def __init__( self, name ):
         self.name = name
         self._value_path = Path( '/dev/gpio', name, 'value' )
 
     @property
     def value( self ):
         return int( self._value_path.read_text() )
 
     @value.setter
     def value( self, value ):
         self._value_path.write_text( str( value ) )
 
 my_input = Gpio('my-input')
 my_output = Gpio('my-output')
 
 print( my_input.value )
 print( my_output.value )
 my_output.value = 1