[RFC] Qi Bootmenu

Carsten Haitzler (The Rasterman) raster at rasterman.com
Fri Oct 9 05:35:14 CEST 2009

On Thu, 8 Oct 2009 22:50:00 +0200 Marc Andre Tanner <openmoko at brain-dump.org>

> Hi all,
> I have been lurking around on various openmoko mailing lists for quite 
> some time (about 1.5 years) but so far I didn't have the time to actually 
> contribute anything useful because of study and work related activities. 
> However during the last few days I actually had some time to waste.
> I therefore looked around for possible projects and found the boot menu
> thingy which interested me for quite some time because it involves various
> different system parts.
> I have seen in the mailing list archives that some people have actually 
> already started to work on projects[0] with similar goals but as far as I
> know they weren't really finished and/or customized for the Freerunner.
> The closest thing to a working solution is probably kexecboot[1].
> So here are my random thoughts on the subject, comments are appreciated.
> Goals
> =====
>  - The user should be able to select which image to boot from 
>    (surprised heh ;)
>  - The image could also provide a minimal system rescue environment
>    that is a sshd server which allows remote access to fix certain
>    things.
>  - In order for this to be useful it needs to be fast. Nobody wants
>    to wait 10+ seconds just to select which image to boot. Speed is
>    therefore the most important factor.
> Overview
> ========
>  - The whole system could be packaged into an initramfs
>  - Ideally I would like to store the boot menu image in NAND flash. 
>    This would ensure that it is always around and different SD
>    based images could be booted with it.
>    The boot sequence would look something like this:
>     - Bootloader (Qi) loads minimal kernel
>     - kernel extracts initramfs /init is executed
>     - application scans for system images on SD card, presents boot menu
>     - selected kernel is started via kexec
> Bootloader (Qi)
> ===============
>  - I would like to change the default boot sequence to first look
>    for the special bootmenu image in the kernel NAND flash partition, 
>    if this is not found the boot sequence should proceed with the SD card.
>    The user can of course still use the hardware buttons to skip the 
>    NAND boot and by pass the bootmenu system.
>    The NAND kernel partition is 8MB large so we need to fit the kernel +
>    initramfs in there.
> Kernel
> ======
>  - optimized for size just the absolutely necessary tings
>    should be compiled in. The gta02_micro_defconfig will be starting
>    point for this. Is it still up to date/maintained?
>  - compress? Recent kernels can be compressed using LZMA
>    Question is if this would actually speed up anything?
>    Answer depends on where the bottleneck is in data throughput
>    or computing power. What is the expected data transfer rate
>    from NAND flash?
>  - disable console output completely
> Userland
> ========
>  - uClibc
>  - stripped down busybox
>  - kexec-tools
>    They only support zImages however distros ship uImages so
>    we would either have to strip off the uImage header which is
>    probably slow or add uImage support to kexec-tools.
>  - dropbear sshd
>  - bootmenu application (see next section)
> Bootmenu application
> ====================
>  - should be something like kexecboot, however It should be finger friendly.
>  - functionality should be something like this (taken from kexecboot):
>     - read available filesystems from /proc/filesystems
>     - read available partitions from /proc/partitions
>     - try to mount each partition, search for zImage in /boot
>     - present menu
>     - kexec selected kernel
>  - GUI based on elementary with framebuffer support?
>    In theory this would be the best solution because we would
>    use the same technology as in a normal system just with a 
>    different backend.  This should ensure that it's actually
>    finger friendly. Although text entry remains a problem 
>    because the illume keyboard can't be used. But I hope that
>    text entry won't be necessary anyway (no kernel command line
>    changes through the GUI, sorry ;) In practice I don't know 
>    how mature the framebuffer backend actually is and it has 
>    quite a few dependcies[2]:
>     * eina
>     * eet
>           o zlib
>           o libjpeg
>     * evas
>           o freetype

i think you missed fontconfig - though it is optional, all the default themes
for elementary etc. assume fontconfig support for font naming.

>     * ecore
>           o ecore-file
>           o ecore-evas
>           o ecore-input
>           o ecore-job
>           o ecore-txt
>           o libiconv (functionality can be provided by uClibc)
>           o tslib
>     * edje
>           o embryo
>           o lua
>     * libpng

nb. u can drop libpng. if all your image data is inside edje files (or u can
put it inot .eet files too) then you won't need this.

>    I have cross compiled all this and without any special optimisation
>    (I just disabled everything in ./configure which seemed not critical)
>    the whole system is about 6-7MB large this is without the kernel.


>    I am not familiar with the EFL code base but what I have seen
>    so far seems like it isn't really optimized for size. So there could
>    be some potential although it would require some work and upstream 
>    approval.
>    Maybe the idea to use elementary is overkill but what are the 
>    alternatives? 

i'll shime in here. yes. efl has grown over the years, and well - the more
functionality you want, the more space it will take. if you are hell-bent on
smallest size you possibly would just write your own fb gui that is very simple
and ugly (with white/black boxes for example). to reduce complexity i would
even remove fonts. what i'd do is:

1. every bootable os provides as well as kernel in /boot/zImage (or wherever),
it provides a /boot/bootIcon - this is a simple zlib compressed (see zlib docs
on how to simply give it a chunk of data to compress, or decompress). you could
avoid compression if u want, but i think this would be worthwhile. lets say the
icon data is RGBA (lets use a universal format to account for different
devices with different screen depths/formats). aany bootable os must provide
this file or it wont be listed. (yes it's an added requirementm but moving work
to the bootable os's i takes it out of the qui boot image)
2. within the qui boot fs u include some /boot/wallpaper file - same format as
3. you load wallpaper, convert to screen depth in the simplest/dumbest way
(speed isnt important. you are not doing realtime ui rendering). eg for 16bpp
this would be:

unsigned int *inpix;
unsigned short *outpix;

*outpix = (((*inpix & 0xff0000) >> 19) << 11) | (((*inpix & 0xff00) >> 10) <<
5) | ((*inpix & 0xff) >> 3);

i'll leave it up to you to handle other screen formats (32, 24, 18, 15, 12,
8bpp etc.). but one per format.

now blend the icons u find (u'll probably just want to blend agaibnst the
original rgba wallpaper image and then convert thr result to screen format like
above - see google for alpha blending math. its rather simple. it's easy to do,
its much more work to do FAST. here speed isnt important as u are just going to
render this once and put it up - no realtime ui), one at a time on the screen

|             |
| [ 1 ] [ 2 ] |
|             |
| [ 3 ] [ 4 ] |
|             |
| [ 5 ] [ 6 ] |
|             |
... etc.

as many as the screen fits - the icons themselves can just be an image (eg a
penguin) or image + text. u'll probably want to use tslib and get coords when u
press to see if up press on one of them - then boot that. you should adjust the
layout based on screen size. eg for landscape:

|                   |
| [ 1 ] [ 2 ] [ 3 ] |
|                   |
| [ 4 ] [ 5 ] [ 6 ] |
|                   |

this will provide all you need for a grahical boot. it wont be smooth. it wont
scroll or animate. it wont let you add much more complexity without a lot of
work (eg configuration panels or more than the above hyper-simple boot), but it
will function and be very small.

of course it's easy for me to say this. i've done all this kind of stuff
before. many times. in fact deep down inside efl are semblances of some of
this, as just a subset of all that efl does. but it does so much more so it's
not small. in return for that footprint you get a small mountain of features.
but as i said - easy for me to say the above. i can do it in my sleep -
it'sw hat i do, but it's up to you to decide if you are up to doing it at this
low level or not. for any reasonable app you'd end up using enough of efl's
features to make it worth carrying along its size. it'd be worth the expense,
but... for you i don't know if you will ever use all those features. it may
simply not be worth it. as long as u use efl your image is not going to be that
small. then again you are adding dropbear and thus also enough network config
tools to set up usbnet - what about wifi? wireless tools too? how much is the
image size when you remove any of the ui bits - all your other parts (libc,
busybox, dropbear, network tools to bring up usbnet and/or wifi, wireless
tools, dhclient if u have wifi... etc. first see how big that is. how big is
it? then relative to that, look at ui.

one thing i can suggest. you can drop edje and elementary and do this in just
ecore_evas + evas. you could even drop eet here. just 1 image format loader (eg
libpng), and you'd be able to i think have a subset of ecore (ecore,
ecore_evas, ecore_input, ecore_fb), and just evas + buffer, software_generic
and fb engine and just png loader module. no savers modules.

now you'd need to create all your own "widgets" - but you could stick to a
simple design as above just an array of icons. load the icon files (now u can
make them .png files in the boot dirs of the os's) and put them on the screen.
you can now easily add callbacks for the mouse down (or up really) on each icon
and boot the appropriate os. wallpaper can also be a png file in the qui boot
fs. you will be using efl at a lower level. you handle the callbacks directly
and place the objects yourself (and handle canvas resizes - yes it can happen
even on the fb. eg a resolution change, but in general handling this right
just handles the inital fb size right anyway). this will mean you donthave to
handle rendering code and different screen formats, image loading or tslib
interfacing etc. it should have you a much reduced efl footprint. but keep you
from the lowest ugliest bits. hell if you keep all the "os info for the ui"
inside the png font handling is moot. u will still need freetype - but u just
put name of the os image into the icon itself (nothing 10 seconds in gimp cant

so to repeat

1. either full efl, elementary etc. - but this will be a big footprint. always
2. subset of efl and keep your ui simple eg as i described above and punt off
all the os identification to a png icon as i described above and justddumbly
display it and handle events when the user presses it. smaller than full efl
but not totally minimal.
3. do it all yourself at the lowest levesl. as small as it will get but by far
the most amount of work for you.

> Proof of Concept
> ================
> As a proof of concept I started to write a simple shell script (well
> in the beginning it was simple in the meantime it evolved in kind of 
> mini build system, maybe something like OpenWRT could be used but I
> wanted a simple solution where I actually understand what's going on) 
> which downloads and cross compiles everything with an uclibc based 
> toolchain.
> So far I have cross compiled all the components mentioned in this 
> post the result is about 6-7MB large.
> I then tried to run the elementary dialog application from the 
> elementary wiki page[3] in a chrooted system and this works
> (although there seems to be a problem with the touchscreen which
> doesn't quite work right and sometimes even causes a segfault).

do you have ts calibration working? you may actually have problems here in that
if the ts is not calibrated and u dont have the right calibration data, it may
not be totally useful. but this depends from device to device. as for segv.
backtraces please! :)

> Another issue is that I currently don't get any console output when
> booting from flash with Qi. Although I've added loglevel=8 to Qi's
> kernel parameters and recompiled+reflashed. Something with the init 
> script and/or missing device nodes might be the problem.
> If you want to help then download the scripts and read the README
> file of the source tarball.
>  http://www.brain-dump.org/tmp/qi-bootmenu-system/qi-bootmenu-system.tar.bz2
> Once you have a rootfs.tar.gz file generated (after ./build.sh &&
> ./initramfs.sh && ./package.sh) copy it over to your Freerunner.
> Bind mount /proc and /dev to the corresponding directories and try 
> it out:
>  mkdir rootfs
>  tar -C rootfs -xzf rootfs.tar.gz 
>  mount -t proc /proc rootfs/proc
>  mount -o bind /dev rootfs/dev
>  chroot rootfs /usr/bin/ash
>  export ELM_ENGINE=fb
>  export ELM_FONT_PATH=/usr/share/fonts
>  dialog "Hello world, works?"
> My current plan is to fix the initramfs console output (ideas what might
> be wrong?). Next step is to launch the elementary dialog app from the init
> script. Then shrink/optimize everything until the boot time is acceptable 
> (or give up if we don't reach that point). And only then start to program 
> the elementary based kexecboot replacement. This would be my first EFL
> application which means I will have to do some research first.
> Comments and/or contributions are welcome and appreciated.
> Happy Hacking,
> Marc
> [0] http://thread.gmane.org/gmane.comp.handhelds.openmoko.devel/2011
> [1] http://git.linuxtogo.org/?p=groups/kexecboot/kexecboot.git
> [2]
> http://www.brain-dump.org/blog/entry/132/On_the_way_towards_a_minimal_elementary_based_boot_system
> [3] http://trac.enlightenment.org/e/wiki/Elementary
> -- 
>  Marc Andre Tanner >< http://www.brain-dump.org/ >< GPG key: CF7D56C0
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The Rasterman (Carsten Haitzler)    raster at rasterman.com

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