git.kernel.org.pub.scm.utils.i2c-tools/eeprom/decode-edid

#!/usr/bin/perl -w
#
# Copyright (C) 2003-2008 Jean Delvare <jdelvare@suse.de>
#
#    This program is free software; you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation; either version 2 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program; if not, write to the Free Software
#    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
#    MA 02110-1301 USA.
#
# EEPROM data decoding for EDID. EDID (Extended Display Identification
# Data) is a VESA standard which allows storing (on manufacturer's side)
# and retrieving (on user's side) of configuration information about
# displays, such as manufacturer, serial number, physical dimensions and
# allowed horizontal and vertical refresh rates.
#
# Using the eeprom kernel driver, you have two possibilities to
# make use of these data:
#  1* The ddcmon script.
#  2* This script.
# Both solutions will return a different kind of information. The first
# method will report user-interesting information, such as the model number
# or the year of manufacturing. The second method will report video-card-
# interesting information, such as video modes and refresh rates.
#
# Note that this script does almost nothing by itself. It simply converts
# what it finds in /proc to binary data to feed the parse-edid program.
# The parse-edid program was written by John Fremlin and is available at
# the following address:
#   http://john.fremlin.de/programs/linux/read-edid/

use strict;
use Fcntl qw(:DEFAULT :seek);
use vars qw($bus $address);
use constant PROCFS => 1;
use constant SYSFS  => 2;

# parse-edid will typically be installed in /usr/sbin or /usr/local/sbin
# even though regular users can run it
$ENV{PATH} .= ':/usr/local/sbin'
	if $ENV{PATH} !~ m,(^|:)/usr/local/sbin/?(:|$),
	&& -x '/usr/local/sbin/parse-edid';
$ENV{PATH} .= ':/usr/sbin'
	if $ENV{PATH} !~ m,(^|:)/usr/sbin/?(:|$),
	&& -x '/usr/sbin/parse-edid';

sub edid_valid_procfs
{
	my ($bus, $addr) = @_;

	open EEDATA, "/proc/sys/dev/sensors/eeprom-i2c-$bus-$addr/00";
	my $line = <EEDATA>;
	close EEDATA;
	return 1
		if $line =~ m/^0 255 255 255 255 255 255 0 /;
	return 0;
}

# Only used for sysfs
sub rawread
{
	my ($filename, $length, $offset) = @_;
	my $bytes = '';

	sysopen(FH, $filename, O_RDONLY)
		or die "Can't open $filename";
	if ($offset)
	{
		sysseek(FH, $offset, SEEK_SET)
			or die "Can't seek in $filename";
	}

	$offset = 0;
	while ($length)
	{
		my $r = sysread(FH, $bytes, $length, $offset);
		die "Can't read $filename"
			unless defined($r);
		die "Unexpected EOF in $filename"
			unless $r;
		$offset += $r;
		$length -= $r;
	}
	close(FH);

	return $bytes;
}

sub edid_valid_sysfs
{
	my ($bus, $addr) = @_;
	my $bytes = rawread("/sys/bus/i2c/devices/$bus-00$addr/eeprom", 8, 0);

	return 1
		if $bytes eq "\x00\xFF\xFF\xFF\xFF\xFF\xFF\x00";
	return 0;
}

sub bus_detect
{
	my $max = shift;

	for (my $i=0; $i<$max; $i++)
	{
		if (-r "/proc/sys/dev/sensors/eeprom-i2c-$i-50/00")
		{
			if (edid_valid_procfs($i, '50'))
			{
				print STDERR
					"decode-edid: using bus $i (autodetected)\n";
				return $i;
			}
		}
		elsif (-r "/sys/bus/i2c/devices/$i-0050/eeprom")
		{
			if (edid_valid_sysfs($i, '50'))
			{
				print STDERR
					"decode-edid: using bus $i (autodetected)\n";
				return $i;
			}
		}
	}

	return; # default
}

sub edid_decode
{
	my ($bus, $addr, $mode) = @_;

	# Make sure it is an EDID EEPROM.

	unless (($mode == PROCFS && edid_valid_procfs ($bus, $addr))
	     || ($mode == SYSFS  && edid_valid_sysfs  ($bus, $addr)))
	{
		print STDERR
			"decode-edid: not an EDID EEPROM at $bus-$addr\n";
		return;
	}

	$SIG{__WARN__} = sub { };
	open PIPE, "| parse-edid"
		or die "Can't open parse-edid. Please install read-edid.\n";
	delete $SIG{__WARN__};
	binmode PIPE;

	if ($mode == PROCFS)
	{
		for (my $i=0; $i<=0x70; $i+=0x10)
		{
			my $file = sprintf '%02x', $i;
			my $output = '';
			open EEDATA, "/proc/sys/dev/sensors/eeprom-i2c-$bus-$addr/$file"
				or die "Can't read /proc/sys/dev/sensors/eeprom-i2c-$bus-$addr/$file";
			while(<EEDATA>)
			{
				foreach my $item (split)
				{
					$output .= pack "C", $item;
				}
			}
			close EEDATA;
			print PIPE $output;
		}
	}
	elsif ($mode == SYSFS)
	{
		print PIPE rawread("/sys/bus/i2c/devices/$bus-00$address/eeprom", 128, 0);
	}

	close PIPE;
}

# Get the address. Default to 0x50 if not given.
$address = $ARGV[1] || 0x50;
# Convert to decimal, whatever the value.
$address = oct $address if $address =~ m/^0/;
# Convert to an hexadecimal string.
$address = sprintf '%02x', $address;

# Get the bus. Try to autodetect if not given.
$bus = $ARGV[0] if defined $ARGV[0];
$bus = bus_detect(8) unless defined $bus;

if(defined $bus)
{
	print STDERR
		"decode-edid: decode-edid version 1.1\n";
	if (-r "/proc/sys/dev/sensors/eeprom-i2c-$bus-$address")
	{
		edid_decode ($bus, $address, PROCFS);
		exit 0;
	}
	elsif (-r "/sys/bus/i2c/devices/$bus-00$address")
	{
		edid_decode ($bus, $address, SYSFS);
		exit 0;
	}
}

print STDERR
	"EDID EEPROM not found.  Please make sure that the eeprom module is loaded.\n";
print STDERR
	"Maybe your EDID EEPROM is on another bus.  Try \"decode-edid ".($bus+1)."\".\n"
	if defined $bus;