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tedder/vc2.py

Created Nov 2, 2018
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py check throttling on raspberry pi
# the following is distilled (reduced) from `py-videocore`, which has a larger purpose but
# happens to include these methods. The following has a MIT license.
# source: https://github.com/nineties/py-videocore
import os
from array import array
from struct import calcsize, pack_into, unpack_from
from fcntl import ioctl
IOCTL_MAILBOX = 0xC0046400 # _IOWR(100, 0, char *)
IOCTL_BUFSIZE = 1024
PROCESS_REQUEST = 0x00000000
REQUEST_SUCCESS = 0x80000000
PARSE_ERROR = 0x80000001
class MailBoxException(Exception):
'mailbox exception'
class MailBox(object):
def __init__(self):
self.fd = os.open('/dev/vcio', os.O_RDONLY)
def close(self):
if self.fd:
os.close(self.fd)
self.fd = None
def __enter__(self):
return self
def __exit__(self, exc_type, exc_value, traceback):
self.close()
return exc_value is None
def _simple_call(self, name, tag, req_fmt, res_fmt, args):
'Call a method which has constant length response.'
# Since the mailbox property interface overwrites the request tag buffer for returning
# values to the host, size of the buffer must have enough space for both request
# arguments and returned values. It must also be 32-bit aligned.
tag_size = (max(calcsize(req_fmt), calcsize(res_fmt)) + 3) // 4 * 4
buf = array('B', [0]*IOCTL_BUFSIZE)
pack_into('=5L' + req_fmt + 'L', buf, 0,
*([24 + tag_size, PROCESS_REQUEST, tag, tag_size, tag_size] + args + [0]))
ioctl(self.fd, IOCTL_MAILBOX, buf, True)
r = unpack_from('=5L' + res_fmt, buf, 0)
if r[1] != REQUEST_SUCCESS:
raise MailBoxException('Request failed', name, *args)
assert(r[4] == 0x80000000 | calcsize(res_fmt))
return r
@classmethod
def _add_simple_method(cls, name, tag, req_fmt, res_fmt):
def f(self, *args):
r = self._simple_call(name, tag, req_fmt, res_fmt, list(args))[5:]
n = len(r)
if n == 1:
return r[0]
elif n > 1:
return r
setattr(cls, name, f)
MAILBOX_METHODS = [
('get_temperature', 0x00030006, 'L', 'LL'),
('get_max_temperature', 0x0003000a, 'L', 'LL'),
('get_throttled', 0x00030046, '', 'L'),
]
for name, tag, req_fmt, res_fmt in MAILBOX_METHODS:
MailBox._add_simple_method(name, tag, req_fmt, res_fmt)
m = MailBox()
print("throttled?", m.get_throttled())
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