Editing PsionLX (section)

=== Boot sequence ===

[[File:PsionLX beta splash screen.png|thumb|300px|Psion's 800 × 600 PsionLX boot splash, from the <code>gpe-bootsplash</code> recipe in Psion's tree]]
The netBook Pro's firmware bootloader, BooSt, loads an operating system image named <code>nBkProOs.img</code> from internal NAND or from a CompactFlash card. BooSt reports itself as "Psion Teklogix netBook2 BooSt".<ref name="boostdongle" /> For Linux the image is a kernel and initial ramdisk wrapped in a 256-byte BooSt header. <code>netbook-booting.txt</code> documents the header: platform ID <code>0x326B426E</code>, load offset <code>0x408000</code>, and image flags <code>0x10003</code> for a CF image (maximum 8,388,608 bytes) or <code>0x10013</code> for a NAND image (maximum 3,702,784 bytes). Bit 16 marks the payload as zlib-compressed and bit 4 copies it to the OS partition.<ref name="anon-lt" /> A 2007 analysis found extra start-up code in Psion's boot images, which sets up the hardware and moves the kernel and ramdisk into place, and for which no source has been found.<ref name="hpcf-oldman-0711" />

The kernel is <code>2.6.9-rc1-bk18-nb1</code>. The same forum analysis found the kernel source in Psion's archive identical to 2.6.9-rc1-bk18 with <code>linux-2.6.9-pre1-bk18-nbp1.patch</code>, published in Koen Kooi's directory at linuxtogo.org, applied.<ref name="hpcf-oldman-0711" /> Psion's image also carries module paths for <code>2.4.26-vrs1-pxa1-nb1</code>, and the tree has a 2.4.26 kernel recipe, so a 2.4 kernel was built for the machine as well.<ref name="kernel-strings" /><ref name="oe-tree" />

The initial ramdisk script, "Netbook LX initial ramdisk boot script", handles both kernel series. Under 2.4 it loads the <code>i2c</code> and <code>i2ckbd</code> keyboard modules; under 2.6 it prints "Running Linux 2.6 System". It then:<ref name="initrd" />

# mounts the first CF partition read-only and, if it holds an executable <code>NBLXLoad.sh</code>, runs it (this is how a new system was written to the internal flash);
# tries to mount the internal NAND as JFFS2 (<code>/dev/mtdblock/0</code>) as the root filesystem;
# if that fails, tries the second CF partition (<code>/dev/hda2</code>);
# pivots into the root filesystem, leaving the ramdisk at <code>/initrd</code>, and starts <code>/sbin/init</code>.

The ramdisk stays mounted at <code>/initrd</code> because it holds the kernel modules. The image recipe points <code>/lib/modules</code> at <code>../initrd/lib/modules</code> for that reason.<ref name="oe-meta" />

On the root filesystem, <code>gpe-bootsplash</code> draws Psion's splash, and <code>gpe-dm</code> starts the kdrive X server on the framebuffer and runs the scripts in <code>/etc/X11/Xinit.d</code>. The last of them, Psion's <code>99psion-session</code>, hands the display to user <code>lx</code>:<ref name="oe-tree" /><ref name="rtc-docs" />

<pre>
chown lx /dev/dsp /dev/mixer
if ! grep -q '^lx::' /etc/passwd; then
  exec gpe-login
else
  ln -s /var/tmp/xsession-errors.lx /home/lx/.xsession-errors
  exec su lx -c /etc/X11/Xsession >> /home/lx/.xsession-errors 2>&1
fi
</pre>

The session then runs Psion's <code>95psion-apps</code>, which copies Psion's button bar layout into the user's home directory ("this also neatly avoids the annoying welcome screen and timezone setter", in the script's own comment), and starts Matchbox with Psion's session file:<ref name="oe-tree" />

<pre>
gpe-soundserver &
gpe-appmgr -d -r &
matchbox-panel --orientation south --size 48 --no-menu &
exec matchbox-window-manager $@
</pre>