How to hotswap Ultrabay devices

The following discusses hotswap (AKA "hotplug") of devices in the UltraBay.

When using the ide-disk driver

The following applies if you use the ide-disk driver for the UltraBay device.

Hotswapping is supposed to be supported as well, using either hdparm/Debian hotswap or lt_hotswap to (un)register IDE devices. The latter is the recommended method with kernels from 2.6, since it will leave DMA working. However, for recent models (R52, T43, X41, Z60 and later) no method is known to work while maintaining DMA support; see Problems with SATA and Linux.

Only IDE devices (HDD's, optical drives, zip drives) require special treatment - batteries, floppies and other devices can just be pulled from the bay, provided they are not mounted or in use at the time. However, you should still power them down first using the ibm-acpi eject function.

The ibm-acpi kernel module has an eject function (# echo eject > /proc/acpi/ibm/bay). This only manages the ACPI calls to power down the device and the bay. It does not actually unregister the device from the IDE driver. # cat /proc/acpi/ibm/bay shows "unoccupied" unless an IDE device is present, but the eject function still works and should still be used.

To unregister the device, you can either use the Debian hotswap package, or lt_hotswap.

Debian hotswap also allows the drive to be swapped as a normal user by default, which is useful. You should use hotswap to unregister the device and then # echo eject > /proc/acpi/ibm/bay. However, if you use this method on a 2.6 kernel, you will loose DMA support for the reinserted drive. This is due to kernel issues. This method was reported to work on a ThinkPad T23 (kernels 2.6.8.1, 2.6.14.2 and 2.6.15-arch) and T42 (kernel 2.6.13), but fails on a ThinkPad T43 (kernel 2.6.14.3).

lt_hotswap is now the recommended method to un- and reregister the IDE device. It installs as a kernel module and has support for automatically unregistering the device when the eject event is generated by ibm-acpi. It will leave DMA support intact. It has supported to work on a ThinkPad T22 and T40 and should work with many other models (but not recent models which require the ata_piix driver for disk DMA support).

When using the ata_piix driver

The following applies when using the ata_piix driver, which is necessary for many recent ThinkPad models that use an Intel ICH6-M controller. See also Problems with SATA and Linux.

Mainline kernels cannot yet reliably recognize newly (re-)inserted UltraBay drives without a reboot. There are experimental hotplug patches against 2.6.16.16 here (see also this thread). This was confirmed to work on a ThinkPad T43.

If your kernel was patched to support ata_piix hotplug (don't try it otherwise!) then issue the following after inserting an UltraBay drive to rescan the port:

# echo 0 0 0 >  /sys/class/scsi_host/host1/scan

The inserted drive should now be recognized by the kernel, and appropriate /dev/* entries created automatically (e.g., by udev).

You can safely shut down the drive by issuing the following (this works with all recent mainline kernels):

# echo 1 > /sys/class/scsi_device/1\:0\:0\:0/device/delete
# echo eject >  /proc/acpi/ibm/bay

The drive can now be ejected.

Scripts for hotswapping

The following scripts and acpid daemon configuration files do the following:

• Automatically unmounts the relevant filesystems and power off the UltraBay when the UltraBay eject lever is released. Screams if some filesystem can't be unmounted.
• Rescans the UltraBay port when then UltraBay eject lever is pushed back in.

They assumes you're using the ata_piix driver with an appropriate kernel (see above).

Create /usr/local/sbin/ultrabay_close with permissions 755:

#!/bin/bash
echo 12 > /proc/acpi/ibm/beep
sleep 3  # disk spinup
echo 0 0 0 > /sys/class/scsi_host/host1/scan

Create /usr/local/sbin/ultrabay_open with permissions 755:

#!/bin/bash

# Umount the filesystem(s) backed by the given major:minor device(s)
unmount_rdev() { perl - "$@" <<'EOPERL'  # let's do it in Perl
	for $major_minor (@ARGV) {
		$major_minor =~ m/^(\d+):(\d+)$/ or die;
		push(@tgt_rdevs, ($1<<8)|$2);
	}
	open MOUNTS,"</proc/mounts" or die "$!";
	while (<MOUNTS>) {
		($dev,$dir)=split;
		next unless -b $dev;  $rdev=(stat($dev))[6];
		next unless grep($_==$rdev, @tgt_rdevs);
		system("umount","-v","$dir")==0  or  $bad=1;
	}
	exit 1 if $bad;
EOPERL
}

SYSDIR='/sys/class/scsi_device/1:0:0:0/device'
if [ -d $SYSDIR ]; then
	# Unmount filesystems backed by this device
	unmount_rdev `cat $SYSDIR/block\:*/dev     \
	                  $SYSDIR/block\:*/*/dev`  \
	|| {
		echo 10 > /proc/acpi/ibm/beep; 
		exit 1;
	}
	# Unregister this SCSI device:
	echo 1 > $SYSDIR/delete
fi
# Turn off power to the UltraBay:
echo eject > /proc/acpi/ibm/bay
# Tell the user we're OK
echo 12 > /proc/acpi/ibm/beep

Create /etc/acpi/events/ultrabay-close.conf:

event=ibm/bay MSTR 00000001 00000000
action=/usr/local/sbin/ultrabay_close

Create /etc/acpi/events/ultrabay-open.conf:

event=ibm/bay MSTR 00000003 00000000
action=/usr/local/sbin/ultrabay_open

Restart acpid.

HAL support

Many programs, KDe included, rely on Template:HAL to get notifications and information about device hotplugging. You need to tell HAL that devices connected the UltraBay port are hotpluggable.

By default, HAL doesn't know that UltraBay devices are hotpluggable:

# UDI=`hal-find-by-property --key storage.physical_device --string /org/freedesktop/Hal/devices/pci_8086_2653_scsi_host_scsi_device_lun0`
# hal-get-property --udi $UDI --key block.device
/dev/sdb
# hal-get-property --udi $UDI --key storage.hotpluggable
false

To fix this, create the file /org/freedesktop/Hal/devices/pci_8086_2653_scsi_host_scsi_device_lun0 as follows:

<?xml version="1.0" encoding="UTF-8"?> <!-- -*- SGML -*- --> 

<deviceinfo version="0.2">
  <device>

    <!-- UltraBay Devices -->
    <match key="storage.bus" string="scsi">
      <match key="storage.physical_device" string="/org/freedesktop/Hal/devices/pci_8086_2653_scsi_host_scsi_device_lun0">
        <merge key="storage.hotpluggable" type="bool">true</merge>
      </match>
    </match>

  </device>
</deviceinfo>

When you now re-plug the device, it will get marked correctly:

# UDI=`hal-find-by-property --key storage.physical_device --string /org/freedesktop/Hal/devices/pci_8086_2653_scsi_host_scsi_device_lun0`
# hal-get-property --udi $UDI --key block.device
/dev/sdb
# hal-get-property --udi $UDI --key storage.hotpluggable
true

Above, the "8086_2653" gives the PCI ID of the Intel 82801FBM southbrdige. If your model has a different southbridge, subsistute the corresponding PCI ID (and report in the talk page).