Update autocons.py

This is the version that landed in xCAT genesis

misc/autocons.py

@@ -0,0 +1,57 @@
+import os
+import struct
+import termios
+
+addrtoname = {
+    0x3f8: '/dev/ttyS0',
+    0x2f8: '/dev/ttyS1',
+    0x3e8: '/dev/ttyS2',
+    0x2e8: '/dev/ttyS3',
+}
+speedmap = {
+    0: None,
+    3: 9600,
+    4: 19200,
+    6: 57600,
+    7: 115200,
+}
+
+termiobaud = {
+    9600: termios.B9600,
+    19200: termios.B19200,
+    57600: termios.B57600,
+    115200: termios.B115200,
+}
+
+def do_serial_config():
+    if 'console=ttyS' in open('/proc/cmdline').read():
+        return None # Do not do autoconsole if manually configured
+    spcr = open("/sys/firmware/acpi/tables/SPCR", "rb")
+    spcr = bytearray(spcr.read())
+    if spcr[8] != 2 or spcr[36] != 0 or spcr[40] != 1:
+        return None
+    address = struct.unpack('<Q', spcr[44:52])[0]
+    tty = None
+    try:
+        tty = addrtoname[address]
+    except KeyError:
+        return None
+    retval = { 'tty': tty }
+    try:
+        retval['speed'] = speedmap[spcr[58]]
+    except KeyError:
+        return None
+    if retval['speed']:
+        ttyf = os.open(tty, os.O_RDWR | os.O_NOCTTY)
+        currattr = termios.tcgetattr(ttyf)
+        currattr[4:6] = [0, termiobaud[retval['speed']]]
+        termios.tcsetattr(ttyf, termios.TCSANOW, currattr)
+    return retval
+
+
+if __name__ == '__main__':
+    serialinfo = do_serial_config()
+    if serialinfo:
+        os.execl(
+            '/bin/setsid', 'setsid', 'sh', '-c',
+            'exec screen -x console <> {0} >&0 2>&1'.format(serialinfo['tty']))