Simple FRU programmer

#!/usr/bin/env python3

import sys
import argparse
import pyipmi.interfaces


class IpmiConn():
    def __init__(self, mmc_addr, mch_url, ipmitool_mode=False):
        if ipmitool_mode:
            self.interface = pyipmi.interfaces.create_interface(
                'ipmitool', interface_type='lan')
        else:
            self.interface = pyipmi.interfaces.create_interface(
                'rmcp', keep_alive_interval=0)
        self.conn = self.mtca_mch_bridge_amc(mch_url, mmc_addr)

    '''
        From https://github.com/kontron/python-ipmi/blob/master/pyipmi/__init__.py#L111
        Example #2: access to an AMC in a uTCA chassis
            slave = 0x81, target = 0x72
            routing = [(0x81,0x20,0),(0x20,0x82,7),(0x20,0x72,None)]
                        uTCA - MCH                        AMC
                    .-------------------.             .--------.
                    |       .-----------|             |        |
                    | ShMC  | CM        |             | MMC    |
         channel=0  |       |           |  channel=7  |        |
     81 ------------| 0x20  |0x82  0x20 |-------------| 0x72   |
                    |       |           |             |        |
                    |       |           |             |        |
                    |       `-----------|             |        |
                    `-------------------´             `--------´
        `------------´     `---´        `---------------´
    '''

    def mtca_mch_bridge_amc(self, mch_url: str, amc_mmc_addr: int):
        '''
        Create a "double bridge" IPMI connection to talk directly to a AMC
        '''
        mtca_amc_double_bridge = [(0x81, 0x20, 0),
                                  (0x20, 0x82, 7),
                                  (0x20, amc_mmc_addr, None)]

        conn = pyipmi.create_connection(self.interface)
        conn.session.set_session_type_rmcp(mch_url)
        conn.session.set_auth_type_user('', '')
        conn.session.establish()
        conn.target = pyipmi.Target(
            ipmb_address=amc_mmc_addr,
            routing=mtca_amc_double_bridge
        )
        return conn


if __name__ == '__main__':
    parser = argparse.ArgumentParser(
        description='Simple FRU programmer'
    )
    parser.add_argument('mch_addr',
                        type=str,
                        help='IP address or hostname of MCH'
                        )
    parser.add_argument('mmc_addr',
                        type=lambda s: 0x70 + 2*int(s[3:], 0) if s.find("AMC") == 0 else int(s, 0),
                        help='IPMB-L address of MMC or "AMCn" (n=1..12)'
                        )
    parser.add_argument('fru_id',
                        type=int,
                        help='0=AMC, 1=RTM, 2=FMC1, 3=FMC2'
                        )
    parser.add_argument('file_name',
                        type=str,
                        help='Bin file for FRU'
                        )
    parser.add_argument('-d', '--debug',
                        action='store_true',
                        help='pyipmi debug mode'
                        )
    args = parser.parse_args()

    ipmi = IpmiConn(args.mmc_addr, args.mch_addr)

    with open(args.file_name, "rb") as f:
        fru_data = f.read()

    fru_len = len(fru_data)

    ipmi.conn.write_fru_data(fru_data, fru_id=args.fru_id)
    fru_data_verify = ipmi.conn.read_fru_data(fru_id=args.fru_id, count=fru_len)
    fru_data_verify = fru_data_verify[:fru_len]

    if fru_data != fru_data_verify:
        print('FRU verify error!', file=sys.stderr)
        exit(1)

    print('FRU written and verified.\n')