Testing this on my Pre2 running #webOS 2.2.4 and works fine, so far :)

See the forum thread here, check out the #1 post, then follow the detail steps below:
1. Download luna.conf.patch for webOS 2.x from Arthur Thornton (on that #1 post)
3. Download VKB-1.1.4.zip (also on that #1 post, depending on your webOS version)
4. Install luna.conf.patch to your Pre 2 using webOS Quick Install



5. Unzip VKB-1.1.4.zip, you've got VKB.sh and send that file to your Pre 2 (e.g to /media/internal)



6. Accessing linux in your Pre 2 using webOS Quick Install or novaterm through Windows Command Prompt / Linux Terminal
7. Go to /media/internal directory: # cd /media/internal
8. Run this command: # VKB.sh -patch
9. Your Pre 2 will boot automatically
10. You've got the Virtual Keyboard by swiping up from gesture area

You can see the source of this blogpost here. I just re-write on my blogpost according to my own experience, trials and errors :)

I assume that you already have all requirement to connect to your TouchPad (Palm SDK, Linux Access, etc.)

Here's what you have to do:
1. Check the actual space used by /media/internal, write down or take screenshot

# df -h | grep internal

 2. Disconnect cryptofs

# pkill -SIGUSR1 cryptofs

3. Unmount /media/internal

# umount /media/internal

4. Verifying you have clean filesystem, before resizing (in my case, there are differences between boot sector and its backup, but I just choose 'no action' )

# /usr/sbin/fsck.vfat /dev/mapper/store-media

5. Verify how much space used by /media/internal

# lvscan | grep media

6. Decide and take space allocated for ext3fs partition (I took 2GB ext3fs partition for DebianChroot, so I resize /dev/mapper/store-media became 10.64G, from 12.64G)

# resizefat /dev/mapper/store-media 10.64G

8. Use free 2G partition to make ext3fs partition

# lvcreate -l 100%FREE -n ext3fs store

9. Format the partition with ext3 filesystem

# mkfs.ext3 /dev/mapper/store-ext3fs

10. Make the filesystem writable

# mount -o remount,rw /

11. Make mount directory

# mkdir /media/ext3fs

12. Add a line in /etc/fstab to automount ext3fs partition on boot up

# echo "/dev/mapper/store-ext3fs /media/ext3fs auto noatime 0 0" >> /etc/fstab

13. Make the filesystem back to read-only

# mount -o remount,ro /

14. Reboot

# reboot

That's it! And I'm pretty sure that you can apply this to any webOS devices :)