IRQ flag mismatch logic in __setup_irq() in Linux kernel for shared interrupts

irq_flags_mismatch.py

#!/usr/bin/python -tt
# -*- coding: UTF-8 -*-
# vim: ts=4 sw=4 et ai si

from __future__ import print_function

import sys
import os

import itertools

__author__ = "Andy Shevchenko"
__license__ = "GPL v2"

PROG = os.path.basename(sys.argv[0])

FLAGS = (
    "SHARED",   # Shared
    "TRIG",     # Trigger type
    "ONESHOT",  # One short
    "PERCPU",   # Per CPU
)

# Leftmost requires the rest to be the same
RULES = (
    ("SHARED",  "SHARED",   "TRIG",     "ONESHOT"),
    ("PERCPU",  "PERCPU"),
)

def codebase(old, new):
    shared = 1 << FLAGS.index("SHARED")
    trig = 1 << FLAGS.index("TRIG")
    oneshot = 1 << FLAGS.index("ONESHOT")
    percpu = 1 << FLAGS.index("PERCPU")

#    if (!((old->flags & new->flags) & IRQF_SHARED) ||
#        (oldtype != (new->flags & IRQF_TRIGGER_MASK)) ||
#        ((old->flags ^ new->flags) & IRQF_ONESHOT))
#            goto mismatch;
#
#    if ((old->flags & IRQF_PERCPU) !=
#        (new->flags & IRQF_PERCPU))
#            goto mismatch;

    if (not ((old & new) & shared) or
            ((old & trig) != (new & trig)) or
            ((old ^ new) & oneshot)):
        return False

    if (old & percpu) != (new & percpu):
        return False

    return True

def algo(old, new, rules):
    shared = 1 << FLAGS.index("SHARED")
    if not (old & shared) and not (new & shared):
        return False

    for rule in rules:
        c = rule[0]
        if (old & c) or (new & c):
            for x in rule[1:]:
                if (old & x) != (new & x):
                    return False
    return True

def comment(old, new):
    shared = 1 << FLAGS.index("SHARED")
    trig = 1 << FLAGS.index("TRIG")
    oneshot = 1 << FLAGS.index("ONESHOT")
    percpu = 1 << FLAGS.index("PERCPU")

#    /*
#     * Can't share interrupts unless both agree to and are
#     * the same type (level, edge, polarity). So both flag
#     * fields must have IRQF_SHARED set and the bits which
#     * set the trigger type must match. Also all must
#     * agree on ONESHOT.
#     */

    if (old & shared) != (new & shared):
        return False

    if not (old & shared):
        return False

    if (old & trig) != (new & trig):
        return False

    if (old & oneshot) != (new & oneshot):
        return False

    if (old & percpu) != (new & percpu):
        return False

    return True

def conv(flags, value):
    if value:
        x = '|'.join(flags[bit] for bit in range(len(flags)) if (value & (1 << bit)))
    else:
        x = "NONE"
    return "%-2d %-30s" % (value, x)

def go(flags, rules):
    for old, new in itertools.permutations(range(1 << len(flags)), 2):
        real = codebase(old, new)
        a = algo(old, new, rules)
        wish = comment(old, new)
        if (real != wish) or (a != real):
            print(conv(flags, old), conv(flags, new), "\t", real, "\t", wish, "\t", a)

def main(argv):
    flags = FLAGS
    rules = [[1 << FLAGS.index(y) for y in x] for x in RULES]

    go(flags, rules)

if __name__ == "__main__":
    sys.exit(main(sys.argv))