need settle before modprobe $FB for uvesafb

[Richard Hansen]

Binary package hint: initramfs-tools

initramfs-tools version 0.92bubuntu50 removed mknods for /dev/mem and /dev/zero, but they are not created by the time the framebuffer script runs. uvesafb (actually v86d) requires these devices (see bug #285970).

To verify, I modified /usr/share/initramfs-tools/scripts/init-top/framebuffer as follows:

--- /usr/share/initramfs-tools/scripts/init-top/framebuffer~ 2009-09-22 21:47:10.000000000 -0400
+++ /usr/share/initramfs-tools/scripts/init-top/framebuffer 2009-09-27 18:04:57.936614976 -0400
@@ -81,7 +81,17 @@
 esac

 if [ -n "${FB}" ]; then
+ echo "checking if /dev/mem and /dev/zero are present" >&2
+ for i in /dev/mem /dev/zero; do
+ if [ -e $i ]; then
+ echo " $i is present" >&2
+ else
+ echo " $i MISSING" >&2
+ fi
+ done
+ echo "about to run modprobe -q ${FB} ${OPTS}" >&2
  MODPROBE_OPTIONS=-q modprobe ${FB} ${OPTS}
+ echo "done running modprobe -q ${FB} ${OPTS}" >&2
 else
  # If we have no graphics devices, wait for udev to settle;
  # if we still don't have a graphics device, load vesafb

The following is the output I saw after running sudo update-initramfs -u and rebooting:

checking if /dev/mem and /dev/zero are present
  /dev/mem MISSING
  /dev/zero MISSING
about to run modprobe -q uvesafb mode_option=1400x1050
[ 1.474357] uvesafb: Getting VBE info block failed (eax=0x4f00, err=-3)
[ 1.474408] uvesafb: vbe_init() failed with -22
done running modprobe -q uvesafb mode_option=1400x1050

[Richard Hansen (rhansen)]

I added back the mknod lines and uvesafb started working again.

[Scott James Remnant (Canonical) (canonical-scott)]

These are created by udev, which is a pre-req of that script - are you saying that they aren't already there?

[Richard Hansen (rhansen)]

Correct -- /dev/mem and /dev/zero are not there by the time modprobe is invoked. Is it possible that this is a race condition? I noticed "udevadm settle" is run at the end of the script -- think it might help to also run "udevadm settle" before running modprobe?

[Richard Hansen (rhansen)]

I tried adding "udevadm settle" before modprobe and that fixed it.

[Scott James Remnant (Canonical) (canonical-scott)]

On Thu, 2009-10-01 at 03:50 +0000, a7x wrote:

> I tried adding "udevadm settle" before modprobe and that fixed it.
>
Aha! Yes, looking at the script that should fix it.

Thanks for the debugging!

Scott
--
Scott James Remnant
<email address hidden>

[Launchpad Janitor (janitor)]

This bug was fixed in the package initramfs-tools - 0.92bubuntu51

---------------
initramfs-tools (0.92bubuntu51) karmic; urgency=low

  * scripts/init-top/framebuffer: wait for udev to settle before loading
    command-line specified framebuffer driver to ensure that any needed
    device nodes are available. LP: #437871.

 -- Scott James Remnant <email address hidden> Sat, 03 Oct 2009 07:55:35 +0100

[Steven Shiau (stevenshiau)]

One thing I noticed related to initramfs-tools - 0.92bubuntu51 is that if I put
video=uvesafb:1400x1050
in the boot parameter,
in /usr/share/initramfs-tools/scripts/init-top/framebuffer, it runs:
modprobe -q uvesafb mode=1400x1050
instead of
modprobe -q uvesafb mode_option=1400x1050

i.e. it actually uses "mode=" instead of "mode_options".
The kernel module "uvesafb" from 2.6.31-11-generic in the Karmic actually uses the option "mode_option" insetad of "mode"
$ modinfo -F parm uvesafb |grep "video mode"
mode_option:Specify initial video mode as "<xres>x<yres>[-<bpp>][@<refresh>]"

Where am I wrong or is this a bug that the function parse_video_opts in /usr/share/initramfs-tools/scripts/init-top/framebuffer should be fixed?

Thanks.

[Richard Hansen (rhansen)]

It's possibly a bug, but not this one -- I'd recommend filing a new bug report. In the meantime, I think you can work around it by doing "video=uvesafb:mode_option=1400x1050".

[Steven Shiau (stevenshiau)]

Thanks! "video=uvesafb:mode_option=1400x1050". works great here.

[Richard Hansen (rhansen)]

Looks like I already filed bug #366343 about the mode_option issue a while back.