1# Lint as: python2, python3
2# Copyright (c) 2014 The Chromium OS Authors. All rights reserved.
3# Use of this source code is governed by a BSD-style license that can be
4# found in the LICENSE file.
5
6from __future__ import absolute_import
7from __future__ import division
8from __future__ import print_function
9from functools import reduce
10import codecs
11import logging
12import operator
13import os
14import six
15from six.moves import map
16from six.moves import range
17
18
19# TODO: This is a quick workaround; some of our arm devices so far only
20# support the HDMI EDIDs and the DP one at 1680x1050. A more proper
21# solution is to build a database of supported resolutions and pixel
22# clocks for each model and check if the EDID is in the supported list.
23def is_edid_supported(host, width, height):
24    """Check whether the EDID is supported by DUT
25
26    @param host: A CrosHost object.
27    @param width: The screen width
28    @param height: The screen height
29
30    @return: True if the check passes; False otherwise.
31    """
32    # TODO: Support client test that the host is not a CrosHost.
33    platform = host.get_platform()
34    if platform in ('snow', 'spring', 'skate', 'peach_pi', 'veyron_jerry'):
35        if (width, height) in [(1280, 800), (1440, 900), (1600, 900),
36                               (3840, 2160)]:
37            return False
38    if platform in ('kahlee', 'grunt'):
39        if (width, height) in [(3840, 2160)]:
40            return False
41    return True
42
43
44class Edid(object):
45    """Edid is an abstraction of EDID (Extended Display Identification Data).
46
47    It provides methods to get the properties, manipulate the structure,
48    import from a file, export to a file, etc.
49
50    """
51
52    BLOCK_SIZE = 128
53
54
55    def __init__(self, data, skip_verify=False):
56        """Construct an Edid.
57
58        @param data: A byte-array of EDID data.
59        @param skip_verify: True to skip the correctness check.
60        """
61        if not Edid.verify(data) and not skip_verify:
62            raise ValueError('Not a valid EDID.')
63        self.data = data
64
65
66    @staticmethod
67    def verify(data):
68        """Verify the correctness of EDID.
69
70        @param data: A byte-array of EDID data.
71
72        @return True if the EDID is correct; False otherwise.
73        """
74        data_len = len(data)
75        if data_len % Edid.BLOCK_SIZE != 0:
76            logging.debug('EDID has an invalid length: %d', data_len)
77            return False
78
79        for start in range(0, data_len, Edid.BLOCK_SIZE):
80            # Each block (128-byte) has a checksum at the last byte.
81            checksum = reduce(operator.add,
82                              list(map(ord, data[start:start+Edid.BLOCK_SIZE])))
83            if checksum % 256 != 0:
84                logging.debug('Wrong checksum in the block %d of EDID',
85                              start // Edid.BLOCK_SIZE)
86                return False
87
88        return True
89
90
91    @classmethod
92    def from_file(cls, filename, skip_verify=False):
93        """Construct an Edid from a file.
94
95        @param filename: A string of filename.
96        @param skip_verify: True to skip the correctness check.
97        """
98        if not os.path.exists(filename):
99            raise ValueError('EDID file %r does not exist' % filename)
100
101        if filename.upper().endswith('.TXT'):
102            # Convert the EDID text format, returning from xrandr.
103            data = reduce(operator.add,
104                          [codecs.decode(s.strip(), 'hex') for s in open(filename).readlines()])
105        else:
106            data = open(filename).read()
107        return cls(data, skip_verify)
108
109
110    def to_file(self, filename):
111        """Export the EDID to a file.
112
113        @param filename: A string of filename.
114        """
115        with open(filename, 'w+') as f:
116            f.write(self.data)
117
118
119# A constant object to represent no EDID.
120NO_EDID = Edid('', skip_verify=True)
121