[maemo-developers] Some conceptual doubts

[From: Eero Tamminen]

Hi,

ext Chandra wrote:
> Can anybody clear the below doubts:
> 
> 1) What is the use of "scratchbox-devkit-apt-https-1.0.3-i386.tar.gz" package?
> 
> 2) What is the use of "scratchbox-devkit-doctools-1.0.7-i386.tar.gz"
> package?. It is a document generation tool. We can use this package to
> generate which type of documents?

It provides some documentation generation tools that are needed in
building the source packages included into the SDK.  Other open
source software may also require these (common) documentation
tools for their built to succeed.  But in most cases you can
disable document building if you want to though.  Building
docs can take a long time (I think it's about half of Gtk
package build time).


> 3) What is the use of "scratchbox-devkit-cputransp-1.0.7-i386.tar.gz" package? "CPU Transparency" refers what?

Being able to run ARM binaries on your x86 Desktop Maemo
development environment.

By default GNU autotools (used to configure & build most of open source)
configures the software for the environment where the code is built.
Configuring tests the build environment by building and running small
test binaries.  When you're cross-compiling in the ARM Scratchbox target
on your x86 host, the produced binaries can run only on (real or
emulated) ARM CPU.

Qemu "CPU transparency" method allows these ARM binaries to be
run (transparently) on the qemu user-space emulator and sbrsh
method[1] would run them on a separate ARM machine.

"transparently" meaning that the program or script running the ARM
binary doesn't notice that it was for another CPU architecture,
it behaves like a native one.

[1] Sbrsh is much harder to setup as you need real ARM machine on your
network and NFS export between it and your desktop, but it's sometimes
useful. It's not technically possible for Qemu user-space emulation to
emulate everything.  In practice this problem should be very rare and
concern only certain threaded programs used in building documentation
(which can be resolved by disabling documentation building[2]).

[2] IMHO software should always have a separate build target for
     documentation, it's shouldn't be built by default.  You need new
     docs only when your API changes and you do a new release, so
     re-generating it usually just wastes developer time.


> 4)  What is the use of "Nokia EUSA licensed binary packages" package?

It contains binaries (I think mainly applications) from the device which
Nokia hasn't open sourced (at least yet) and which developers might want
to have present when testing their own software in the SDK.


> 5) In the above query, EUSA refers what?

To the license.  It has many additional limitations compared to Open
Source licenses.


> 6) What is the use of "maemo-sdk-rootstrap_4.1.2_i386.tgz" package?
> 
> 7) In the above query, what is meant by "rootstrap"?

"Rootstrap" is a root file system corresponding to a set of
software that you have on the device.  It's used to "bootstrap"
your development environment for given Maemo operating system
version and CPU architecture.

You cannot install a distribution from scratch, it needs to
be "bootstrapped" with things needed for installing additional
packages to the distribution (same as on Debian & Ubuntu).

Minimal rootstrap include only essential things like package
management, sdk-rootstrap includes also pre-installed development
packages.


> 8) In "Xephyr" command: -ac, -extension, Composite options refers what?

X server XComposite extension provides window content update redirection
(to a pixmap that can be used e.g. as a texture in OpenGL operations)
feature.  This is used by so called composite manager (often part of
window manager) which redirects the top level application window content
to window backbuffers and then composites these window content
(textures) to the screen using different OpenGL transformations.

To know more, read documentation at freedesktop.org and your Linux
distribution Composite manager (KDE v4 kwin, Gnome metacity, Beryl,
Compiz...) source code.


	- Eero