255 lines
10 KiB
Python
255 lines
10 KiB
Python
# MIT License
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#
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# Copyright (c) 2023 Neil Webber
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#
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# Permission is hereby granted, free of charge, to any person obtaining a copy
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# of this software and associated documentation files (the "Software"), to deal
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# in the Software without restriction, including without limitation the rights
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# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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# copies of the Software, and to permit persons to whom the Software is
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# furnished to do so, subject to the following conditions:
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#
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# The above copyright notice and this permission notice shall be included in
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# all copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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# SOFTWARE.
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from collections import namedtuple
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import threading
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from pdptraps import PDPTrap
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# an interrupt is, at the cpu implementation level, just a flavor of trap.
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class InterruptTrap(PDPTrap):
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def __init__(self, pri, vector):
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super().__init__()
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self.pri = pri
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self.vector = vector
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# contains the details for a pending interrupt (see discussion)
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PendingInterrupt = namedtuple(
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'PendingInterrupt', ('pri', 'vector', 'callback'))
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# Interrupts are priority sorted by pri (duh), but (less obviously)
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# two interrupts with the same pri are further priority sorted by
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# vector, with lower vector being higher priority. This calculation
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# encapsulates that into a single integer value, with the knowledge
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# that no vectors can ever be anywhere near as high as 16384.
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def _qpri(pdi):
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return (pdi.pri * 16384) + (16384 - pdi.vector)
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# To cause an interrupt, a device creates a PendingInterrupt containing:
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# pri -- priority
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# vector -- the interrupt vector
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# callback -- see discussion
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#
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# and then calls pend_interrupt() to get things going.
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#
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# The interrupt does not, of course, occur right away; it pends until
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# the processor is willing to accept it. The processor only accepts
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# interrupts at instruction boundaries, and even then only if the current
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# processor priority level is below the interrupt pri.
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#
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# When those conditions occur, the interrupt is accepted by the processor
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# (via a get_pending() method called from the processor). At that time the
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# interrupt request is "granted" and the callback function, if any is
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# provided, is invoked (from the cpu thread).
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#
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# The callback is invoked with no arguments and the return value is ignored.
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# Use partial() or other python techniques if the callback function requires
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# arguments for more context information (most will not).
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#
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# The purpose of this callback protocol is that some devices have internal
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# operations they want to perform when the interrupt is acknowledged, not
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# just when it is first made pending. Callbacks allow for that to happen.
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# CAUTION: The callback obviously executes in a separate thread and
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# will be asynchronous to any device-internal threads.
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#
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# In the simplest/common cases where none of this is needed, the
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# method simple_irq() bundles all this minutia up for the caller.
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class InterruptManager:
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def __init__(self):
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self.pri_pending = 0
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self.requests = []
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self.condition = threading.Condition()
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def simple_irq(self, pri, vector):
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"""Pend an interrupt at the given pri/vector."""
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self.pend_interrupt(PendingInterrupt(pri, vector, callback=None))
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def pend_interrupt(self, irq):
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"""Pend a request for interrupt 'irq'."""
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with self.condition:
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# special case to accelerate zero-to-one common transition
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if not self.requests:
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self.requests = [irq]
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self.pri_pending = irq.pri
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else:
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# multiple identical requests are not pended
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# (it works this way in the hardware too of course --
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# if a device has asserted the interrupt request line
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# but that request hasn't been acknowledged/cleared by
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# by the bus signal protocol yet, you can't assert the
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# same interrupt line again ... it's already asserted)
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if irq not in self.requests:
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self.requests = sorted(self.requests + [irq], key=_qpri)
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self.pri_pending = self.requests[-1].pri
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self.condition.notify_all()
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# called by the processor, to get one pending interrupt (if any).
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# An InterruptTrap with the highest priority is returned, IF it is
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# above the given processor priority. Else None.
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def get_pending(self, processor_pri):
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"""Returns an InterruptTrap, or None."""
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with self.condition:
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try:
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if self.pri_pending > processor_pri:
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irq = self.requests.pop()
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else:
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return None
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except IndexError:
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return None
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else:
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if self.requests:
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self.pri_pending = self.requests[-1].pri
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else:
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self.pri_pending = 0
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if irq.callback:
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irq.callback()
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return InterruptTrap(irq.pri, irq.vector)
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def waitstate(self, processor_pri):
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"""Sit idle until any interrupt happens."""
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with self.condition:
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if self.pri_pending > processor_pri:
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return
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self.condition.wait_for(lambda: self.pri_pending)
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if __name__ == "__main__":
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import unittest
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from functools import partial
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class TestMethods(unittest.TestCase):
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def test__init__(self):
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IM = InterruptManager()
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# initial state starts with no pending interrupts
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self.assertEqual(IM.pri_pending, 0)
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# verify get_pending still "works" (returns None)
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self.assertEqual(IM.get_pending(0), None)
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def test_queue1(self):
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IM = InterruptManager()
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test_pri = 4 # arbitrary
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test_vec = 17 # arbitrary
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IM.simple_irq(test_pri, test_vec)
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self.assertEqual(IM.pri_pending, test_pri)
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iinfo = IM.get_pending(0)
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self.assertEqual(IM.pri_pending, 0)
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self.assertEqual(iinfo.pri, test_pri)
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self.assertEqual(iinfo.vector, test_vec)
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# support function for test cases, do a bunch of actions on an IM
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def _actions(self, IM, prog):
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cpupri = 0
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for action in prog:
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match action[0], action[1]:
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case 'RQ', t:
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IM.simple_irq(*t)
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case 'PRI', cpupri:
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pass
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case 'GET', xt:
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t = IM.get_pending(cpupri)
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if t is None:
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self.assertEqual(t, xt)
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else:
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xpri, xvec = xt
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# If the vector position is a tuple then that
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# means to accept anything in that tuple
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try:
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_ = (t.vector in xvec)
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except TypeError:
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pass
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else:
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xvec = t.vector # i.e., it's ok
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self.assertEqual(t.pri, xpri)
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self.assertEqual(t.vector, xvec)
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case 'CHK', pri:
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self.assertEqual(IM.pri_pending, pri)
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case _:
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raise ValueError("bad action", action)
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def test_mixedops(self):
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testprogs = (
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# (ACTION, ACTION-INFO)
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(('RQ', (4, 44)), # request IRQ 4
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('RQ', (5, 55)), # request IRQ 5
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('GET', (5, 55)), # get one, check that it is 5
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('CHK', 4), # check that pri_pending is 4
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('RQ', (3, 33)), # request IRQ 3
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('CHK', 4), # check that pri_pending is 4
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('RQ', (6, 66)), # request IRQ 6
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('CHK', 6), # check that pri_pending is 6
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('GET', (6, 66)), # get one, check that it is 6
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('CHK', 4), # check that pri_pending is 6
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('GET', (4, 44)), # get one, check that it is 4
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('CHK', 3), # check that pri_pending is 3
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('GET', (3, 33)), # get one, check that it is 3
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('CHK', 0), # check that pri_pending is 0
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('GET', None), # check that getting from empty works
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),
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# check priority filtering
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(('RQ', (4, 44)), # request IRQ 4
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('RQ', (5, 55)), # request IRQ 5
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('PRI', 7), # spl7
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('GET', None), # shouldn't see anything
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('PRI', 5), # spl5
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('GET', None), # still shouldn't see anything
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('RQ', (6, 66)), # request IRQ 6
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('RQ', (7, 77)), # request IRQ 7
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('RQ', (6, 666)), # request IRQ 6
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('RQ', (7, 777)), # request IRQ 7
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('PRI', 6), # spl6
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('GET', (7, (77, 777))), # should get one of these
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('GET', (7, (77, 777))), # should get the other
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('GET', None), # no more
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('PRI', 0), # spl0
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('GET', (6, (66, 666))), # should get one of these
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('GET', (6, (66, 666))), # should get one of these
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('GET', (5, 55)),
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('GET', (4, 44)),
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('GET', None)),
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)
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for tp in testprogs:
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IM = InterruptManager()
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self._actions(IM, tp)
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def test_vectorcallback(self):
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def foo(d):
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d['foo'] = 1234
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foodict = {}
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pfoo = partial(foo, foodict)
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IM = InterruptManager()
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IM.pend_interrupt(PendingInterrupt(4, 888, pfoo))
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iinfo = IM.get_pending(0)
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self.assertEqual(foodict['foo'], 1234)
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unittest.main()
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