#!/bin/bash

# $Id:$
#
# This provides a stripped down 'failsafe' mode for situations
# where X is failing to start up.

# Author: Bryce W. Harrington <bryce@canonical.com>

# Copyright 2007 Canonical, Ltd
#
# This is free software; you may 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,
# or (at your option) any later version.
#
# This 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 with
# the Debian operating system, in /usr/share/common-licenses/GPL;  if
# not, write to the Free Software Foundation, Inc., 59 Temple Place,
# Suite 330, Boston, MA 02111-1307 USA

xorg_conf_failsafe=${BPX_XORG_CONF_FAILSAFE:-"/etc/X11/xorg.conf.failsafe"}
xorg_conf=${BPX_XORG_CONF:-"/etc/X11/xorg.conf"}

run_dexconf=${BPX_RUN_DEXCONF:-"yes"}

# TODO:  This should be set to "vga", however I have been unable to
#        succeed in getting the vga driver running in anything over
#        320x200, which is unusable.  So fallback is disabled for now.
#fallback_driver="vga"
fallback_driver=${BPX_FALLBACK_DRIVER:-"vesa"}

client=${BPX_CLIENT:-"/etc/gdm/failsafeXinit"}
clientargs=${BPX_CLIENTARGS:-$xorg_conf_failsafe}
blacklist=${BPX_BLACKLIST:-"/etc/gdm/failsafeBlacklist"}
main_driver=${BPX_DRIVER:-"vesa"}
checkduration=${BPX_CHECK_DURATION:-30}
failsafe_log=${BPX_LOG:-"/var/log/gdm/failsafe.log"}

server=${BPX_SERVER:-/usr/bin/X}
serverargs=${BPX_SERVERARGS:-"$*"}
if [ -z $serverargs ]; then
    # Use :10 to avoid overwriting the (failed) Xorg.0.log
    serverargs=":10"
fi
serverargs="${serverargs} -br -once -config $xorg_conf_failsafe"
   # -br:      Black background
   # -once:    Terminate server after one session
   # -config:  Specify location of xorg.conf file to use
   #           Note: Only root can specify absolute paths

warn() {
    echo "Warning:  $1" 1>&2
}

is_installed() {
    prog=$1
    need=$2
    /usr/bin/which $prog > /dev/null 2>&1
    err=$?
    if [ ! $err = 0 ]; then
	warn "Could not $need because $prog is not installed ($err)"
	return $err
    fi
    return 0
}

# Tests if the given pciids are in numerical order from least to greatest
# (e.g., $a <= $b <= $c <= ...)
pciids_in_order() {
    lastid=0
    for pciid in $* ; do
        # Strip embedded : and convert hex to dec
        id=$((0x${pciid/:/}))
        if [ $id -lt $lastid ]; then
            return 1
        fi
        lastid=$id
    done
    return 0
}

get_edid() {
    # Retrieve EDID (if get-edid is installed)
    is_installed get-edid "retrieve EDID" || return 1

    # Discard stderr, which is text data about the card
    get-edid 2>/dev/null
}

get_pciids() {
    # Retrieve PCI IDs from discover
    is_installed discover "retreive PCI IDs" || return 1

    discover --enable-all video --format="%i\n"
}

get_driver() {
    EDID=$(get_edid)
    PCIIDS=$(get_pciids)

    if [ "x$EDID" = "x" ]; then
	echo $fallback_driver
	return 1
    elif [ "x$PCIIDS" = "x" ]; then
	echo $fallback_driver
	return 2
    fi

    # TODO:  What if we have multiple pciids?  Assume first for now.
    pciid=$(echo $PCIIDS | head -n 1)

    EDID_MD5=$(echo $EDID | md5sum | head -n1 | cut -d" " -f1)
    matches=$(egrep "^$EDID_MD5|^ANY" $blacklist)
    found="no"
    for line in "$matches"; do
	line=$(echo $line | sed -e "s/ \+/ /")
	range=$(echo $line | cut -d' ' -f 2)
	driver=$(echo $line | cut -d' ' -f 3)
	pciid1=$(echo $range | cut -d- -f 1)
	pciid2=$(echo $range | cut -d- -f 2)

	if [ "x$pciid1" = "x" ]; then
            continue
	elif [ "x$pciid1" = "xANY" ]; then
	    found="yes"
	    break
	elif [ "$pciid1" = "$pciid" ]; then
	    found="yes"
	    break
	elif [ "x$pciid2" = "x" ]; then
            continue
	elif pciids_in_order $pciid1 $pciid $pciid2 ; then
	    found="yes"
	    break
	fi
    done

    if [ $found = "no" ]; then
	echo $main_driver

    else
	# No driver was specified - assume vga
	if [ "x$driver" = "x" ]; then
	    warn "System is blacklisted, but no driver specified; assuming fallback"
	    driver=$fallback_driver
	fi

	echo $driver
    fi

    return 0
}

# Check if we've already attempted a failsafe session without success
if [ -e "$failsafe_log" ]; then
    cur_time=$(date +"%s")
    last_run=$(tail -n 1 $failsafe_log | cut -d' ' -f1)
    time_diff=$(expr $cur_time - $last_run)
    if [ $time_diff -lt $checkduration ]; then
        warn "Failsafe mode was already attempted within $checkduration seconds."
        warn "Falling back to gdm to report the issue."
        exit 1
    fi
fi

# When failsafe mode is activated, check the blacklist for systems we
# know do not support VESA 800x600/256
#      Use EDID + PCI IDs as key to lookup (Can get PCI IDs from discover)
#      If the display does not give EDID info, then use VGA 640x480/16 mode
#      If a matching entry is found, then use VGA 640x480/16 mode
driver=$(get_driver)

if [ "x${run_dexconf}" = "xyes" ]; then
    # Generate an appropriate xorg.conf
    /etc/gdm/failsafeDexconf $driver $xorg_conf_failsafe
    if [ ! -s $xorg_conf_failsafe ]; then
        warn "Could not generate $xorg_conf_failsafe for $driver driver"
        exit 1
    fi
elif [ ! -s $xorg_conf_failsafe ]; then
    warn "Requested to use $xorg_conf_failsafe for $driver driver, but it does not exist"
    exit 1
fi

md5xorg=$(md5sum $xorg_conf)
date +"%s $md5xorg" >> $failsafe_log
if [ $? -ne 0 ]; then
    warn "Cannot write to $failsafe_log"
fi

# TODO:  Start up the failsafe X session using their regular user account

if pidof /usr/sbin/gdm ; then
    clientargs="${clientargs} with-gdm"
fi

echo "xinit $client $clientargs -- $server $serverargs"
xinit $client $clientargs -- $server $serverargs &

sleep 3

# Stop gdm if it's running, otherwise it will attempt to manage the display
# out from under us
if pidof /usr/sbin/gdm ; then
    exec kill -STOP $PPID
fi

# This seems to cause gdm to attempt to start a new x session
#exec kill -USR1 `cat /var/run/gdm.pid`