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14 25 sysfs permissions #26

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14 25 sysfs permissions #26

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168a874
Fix permissions error for /sys/class/gpio/export
aSmig Sep 13, 2022
20653fa
Fix permissions error for /sys/class/gpio/*/value
aSmig Sep 13, 2022
f9991c3
wait for gpio*/value file group initialization
aSmig Sep 13, 2022
84789ac
Improve FMODE naming: SYS->STR
aSmig Sep 13, 2022
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23 changes: 16 additions & 7 deletions gpio/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@
__version__ = '1.0.0'

from threading import Lock
from time import sleep, time
try:
from collections.abc import Iterable
except ImportError:
Expand All @@ -16,7 +17,9 @@
GPIO_ROOT = '/sys/class/gpio'
GPIO_EXPORT = os.path.join(GPIO_ROOT, 'export')
GPIO_UNEXPORT = os.path.join(GPIO_ROOT, 'unexport')
FMODE = 'w+' # w+ overwrites and truncates existing files
FMODE_STR_WO = 'w' # /sys/class/gpio/export is not readable, even by root
FMODE_STR_RW = 'w+' # w+ overwrites and truncates existing files
FMODE_BIN_RW = 'wb+' # Using unbuffered binary IO is ~ 3x faster than text
IN, OUT = 'in', 'out'
LOW, HIGH = 0, 1

Expand Down Expand Up @@ -46,12 +49,18 @@ def __init__(self, pin, direction=None, initial=LOW, active_low=None):

if not os.path.exists(self.root):
with _export_lock:
with open(GPIO_EXPORT, FMODE) as f:
with open(GPIO_EXPORT, FMODE_STR_WO) as f:
f.write(str(self.pin))
f.flush()
gpio_gid = os.stat(GPIO_ROOT).st_gid
value_path = os.path.join(self.root, 'value')
start = time()
# give udev a moment to update the group of newly created files
while os.stat(value_path).st_gid != gpio_gid and time() - start < .5:
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should you throw some kind of error if this ISN'T true after the loop?

sleep(.01)

# Using unbuffered binary IO is ~ 3x faster than text
self.value = open(os.path.join(self.root, 'value'), 'wb+', buffering=0)
self.value = open(os.path.join(self.root, 'value'), FMODE_BIN_RW, buffering=0)

# I hate manually calling .setup()!
self.setup(direction, initial, active_low)
Expand Down Expand Up @@ -100,7 +109,7 @@ def get_direction(self):
Returns:
str: "in" or "out"
'''
with open(os.path.join(self.root, 'direction'), FMODE) as f:
with open(os.path.join(self.root, 'direction'), FMODE_STR_RW) as f:
return f.read().strip()

def set_direction(self, mode):
Expand All @@ -112,7 +121,7 @@ def set_direction(self, mode):
if mode not in (IN, OUT, LOW, HIGH):
raise ValueError("Unsupported pin mode {}".format(mode))

with open(os.path.join(self.root, 'direction'), FMODE) as f:
with open(os.path.join(self.root, 'direction'), FMODE_STR_RW) as f:
f.write(str(mode))
f.flush()

Expand All @@ -125,7 +134,7 @@ def set_active_low(self, active_low):
if not isinstance(active_low, bool):
raise ValueError("active_low must be True or False")

with open(os.path.join(self.root, 'active_low'), FMODE) as f:
with open(os.path.join(self.root, 'active_low'), FMODE_STR_RW) as f:
f.write('1' if active_low else '0')
f.flush()

Expand Down Expand Up @@ -168,7 +177,7 @@ def cleanup(self):

if os.path.exists(self.root):
with _export_lock:
with open(GPIO_UNEXPORT, FMODE) as f:
with open(GPIO_UNEXPORT, FMODE_STR_WO) as f:
f.write(str(self.pin))
f.flush()

Expand Down