Resuming X

At Linux Laptops we have created a fix for the problem of X interacting poorly with suspend/resume on many systems.

  Many (most?) BIOSes fail to save and restore display
  controller chip registers, and X has no protocol to
  be notified of resume events, so on many systems
  suspend/resume is more-or-less incompatible with X.

  The fix below is not perfect because it depends on several
  environmental factors.  According to Dirk Höhndel, future
  versions of X will respond directly to a "resume" event from
  the kernel or from APMD.  In the meantime, this fix works.

  The first part is a tiny C program. It reports the Virtual
  Terminal that currently occupies the display:

-----------------------
/*
 * queryvt.c - ncm - Query current virtual terminal number
 * 
 *  Copyright 1999 by Nathan C. Myers. 
 *     Licensed under the GNU General Public License, version 2.
 */
#include <sys/types.h>
#include <sys/ioctl.h>
#include <linux/vt.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <errno.h>

int
main() {
    int result = 0;
    char twelve = 12;
    int fd = open("/dev/tty0", O_RDWR|O_NDELAY);
    if (fd < 0) {
      fputs("queryvt: cannot open /dev/tty0.\n", stderr);
      exit(-errno);
    }
    result = ioctl(fd, TIOCLINUX, &twelve);
    if (result < 0) {
      fputs("queryvt: cannot query console.\n", stderr);
      exit(-errno);
    }
    exit(result+1);
}
-----------------------

  The second part is a script that goes in /etc/apm/resume.d,
  called xserver-resume. It checks whether X is actually on
  the current display, because X servers tend to crash if they
  receive display events when not in control of the display.

-----------------------
#!/bin/bash
#
#  Copyright 1999 by Nathan C. Myers. 
#     Licensed under the GNU General Public License, version 2.

AUTHDIR=/var/state/xdm/authdir/authfiles
XVIDTUNE=/usr/X11R6/bin/xvidtune
QUERYVT=/usr/local/bin/queryvt

(
 $QUERYVT  # find out which vt is active.
 result=$?
 if \[ $result -ge 7 ]
 then
   # X server is active
   ((xid=${result}-7))
   set $AUTHDIR/A:${xid}-*
   if \[ $# = 1 -a -f "$1" ]; then
     # cycle the display mode to reset display-chip registers.
     DISPLAY=:${xid}.0 XAUTHORITY="$1"   $XVIDTUNE -next
   fi
 fi
 \echo -n  >/dev/tty0
)&
-----------------------

  This solution depends on these enviromental factors:

  1. apmd version 3.0beta8 or later is running:

  Up-to-date versions of apmd support running scripts on suspend
  and resume events.

  2. xdm is running:

  The script needs xdm running so that the X authorization cookie
  needed for the script to talk to the server is in a known place.
  Of course you could hard-code the path to your own authorization
  cookie file, instead, if only you log in.

  3. The XF86Config file has only two, identical, modes:

  The script depends on the command "xvidtune -next" to cause
  no actual change to the display. This means that it works
  only if only a single display resolution is used. For example,
  in the "Monitor" section of my XF86Config file, I have

    Modeline "1024x768a" 78.654 1024 1056 1184 1312 768 772 776 792
    Modeline "1024x768b" 78.654 1024 1056 1184 1312 768 772 776 792

  and no other modelines, and in my subsection "Display" I have

    Modes "1024x768a" "1024x768b"

  Incidentally, "fbset -x" is a good way to produce the correct
  modeline for modern machines, if you have "frame buffer" support
  compiled in, and have booted with a "vga=0x317" kernel option.
  

The approach above works. Still, in the absence of direct X server support it would be much preferable to synthesize keyboard events on the current console:

  ctrl down
  alt down
  numeric '+' down
  numeric '+' up
  alt up
  ctrl up

at a point before X (and X authorization) is involved, rather than trying to talk directly to the X server. This would eliminate the need for the queryvt program, and for the X authorization apparatus in the script.

Does anybody know if this is possible? Please write.