Ikke's Blog

Tonight I wrote some little Python application to play around with Cairo (PyCairo that is), and XShape. The result? Something similar to MacSlow's Cairo-Clock, although much more basic.

You can find the result in my code section.

Just start it in some terminal. Clicking on the clock allows you to move it, clicking it while pressing a shift keys starts resizing mode. When running on top of a terminal/browser/whatever with scrollbars, try to move your pointer close to the clock's circle, inside the area that's normally covered by the clock's window/frame, then use your scrollwheel. As you should notice, the scroll events are not sent to the clock window, but to the underlying window: it's really a circle, not a transparant rectangular window which still catches all events anyway.

Have fun with it!

Edit: there's a little screencast online. Warning: colors look bad, this is caused by the recording software.

Ikke • Technology, Linux, Desktop, Coding Corner 3 comments

As I'm not allowed to code last days (studies >:() I tried to get something working I wanted for a long time: be able to run my favorite media player on my desktop (I must confess that's Amarok), and playback the music using a hifi chain in another room.

As currently I don't have a wifi network at home, I can't do "the real thing" yet, but testing can be done using usbnet (little howto on how to set up that might follow later).

After lots of searching and great help on several IRC channels, I got things working fine now.

Let's start with a little overview of the setup.
Desktop:

• Music player: Amarok using the Xine backend, using alsa
• Streaming server: Icecast2
• Icecast source: gst-launch using the shout2cast sink

770:

• Just the standard audio player

Here's how to set up things correctly:

• Install icecast2 on your system (this is distribution dependant)
• Configure the server. You can run icecast as a system service, or as a normal user. I chose to run it as a normal user:
  • Copy /etc/icecast2/icecast.xml to some directory
  • Change "logdir" to some directory you got write permissions for
  • Start the server: icecast -c icecast.xml (add -b to daemonize)
• Start some media player

• Now we got to get the media player's output to our icecast server. As the 770 cannot playback ogg/vorbis, but can handle mp3, we'll use mp3 here. I know that might be non-free etc, but let's be pragmatic.

  To get the alsa sound to the server, one might use DarkIce, but I could not get this working, so I used a simple gstreamer pipeline instead:gst-launch-0.10 alsasrc device=plughw:0,0 ! audioconvert ! lame ! shout2send mount=amarok

  You might need to change the "device" parameter, you can change the "mount" parameter of shout2send too (although you'll have to adjust the URI used later too, of course). I'm using the default password ("hackme") in this setup, if you don't, or want to set other options, see gst-inspect-0.10 shout2send for more info.

• When that's running fine, open a browser, and go to http://localhost:8000. If all goes well, the "amarok" mount should be listed there. Do not open the stream, as this'd create a loop!
• Finally, launch the audio player on your 770 device, open the menu, "Playlist -> Add Stream...", and enter here the URI of the stream. In my setup, this is http://192.168.2.1:8000/amarok. Now start playback.
• The 770 should buffer some data, then start playback.

Currently, I stream my Amarok's output to my device using usbnet, and got my normal computer speaker connected to the jack output. Works fine :-)

If you're using Amarok too, take a look at the "Web Control" script. When running this script, you can open the 770's browser, and browse to http://192.168.2.1:4774 (adjust the IP). Now you're able to control Amarok from your device, and look at the current playlist. No need to walk to your desktop. The web interface might need some love though.

That's about it, have fun!

Ikke • Networks, Desktop 4 comments

Little update:
1. I got a SoC assignment, at Gentoo. I'll be (actually I am) working on Gentoo's NetworkManager backend and integration into the distribution, next to more general NetworkManager hacking (although some people seem to dislike that somehow :|).
2. I might be able to come to GUADEC, jay!
3. Experimented with SystemTap today. After seeing the DTrace demos at Fosem06, I was fairly impressed. Systemtap is no DTrace-for-Linux yet, but I the scripts I was able to run were pretty promissing.

Little HOWTO (on Gentoo, but should work on other distributions too):
$ (cd into some project folder, I used ~/Projects/systemtap)
$ mkdir elfutils && cd elfutils
$ wget ftp://sources.redhat.com/pub/systemtap/elfutils/elfutils-0.120.tar.gz ftp://sources.redhat.com/pub/systemtap/elfutils/elfutils-portability.patch
$ tar -zxf elfutils-0.120.tar.gz && cd elfutils-0.120
$ cat ../elfutils-portability.patch | patch -p1
$ cd ..
$ cvs -d :pserver:anoncvs@sources.redhat.com:/cvs/systemtap login
(pass is "anoncvs", no quotes)
$ cvs -d :pserver:anoncvs@sources.redhat.com:/cvs/systemtap co systemtap
$ cd src
$ ./configure --prefix=/path/where/you/want/the/stuff --with-elfutils=/path/to/patched/elfutils
I used ~/Projects/inst as prefix (expanded), and ~/Projects/systemtap/elfutils/elfutils-0.120 as elfutils path
$ make
make failed for me (GCC4.1.1) due to usage of -Werror in elfutils. I had to add a -Wno-error in elfutils/elfutils-0.120/src/Makefile.am on the appropriate place (you should be able to do that yourself).
$ make install

Now we need a kernel with debug info, and kprobe support.
$ cd /usr/src/linux
$ make clean
$ make menuconfig
Configure the kernel like you would normally. Make sure you change the "Local version" under "General Setup". I added -dbg to the string I already got there ("-ck1-ikke2-dbg"), so your "normal" kernel modules won't be overwritten.
Then you need these options. This list might not be complete though:
- Instrumentation Support -> Kprobes
- Kernel hacking -> Compile the kernel with debug info
- Kernel hacking -> Compile the kernel with frame pointers (this might not be necessary)
$ make
$ make modules_install
The generated kernel will be big:
# du -sh /lib/modules/2.6.16.18-ck1-ikke2-dbg/ /usr/src/linux/vmlinux
21M /lib/modules/2.6.16.18-ck1-ikke2-dbg/
36M /usr/src/linux/vmlinux
and compilation (actually, linking) might take longer than normally. Used diskspace will be much higher too.

$ cp /usr/src/linux/vmlinux /lib/modules/2.6.18-ck1-ikke2-dbg/
(adjust paths!)

Now install the kernel like you normally would. I didn't put it as my default kernel in grub.conf though.

When you're done, reboot inside the new kernel. I booted into single user mode (by appending "1" to the GRUB line), just to be on the safe side.
Log in as your normal user on the console.

$ cd Projects/systemtap/src/examples/small_demos/
$ ~/Projects/inst/bin/stap top.stp -v
stap will show what it's doing. In the end, sudo will be called to insmod the generated module. Enter your password. Make sure the user is allowed to use sudo with the specific program (run with one more -v to see the specific call).

When it says everything's up and running, try switching console, type in some characters,... And see what system calls these actions generate.
As you're in single user mode, you can only use one tty. Run the stap instance in a screen session to get rid of this ;-)

Whe done, press ^C to quit. You can play around with some other sample scripts too, or try to write one yourself. I didnt manage to get some of the scipts working on my system yet though. Didn't think too much about it either :-)

Thats it, have fun!

4. Started reading "Linux Device Drivers, 3th edition", at chapter 6 now. Cool stuff, concurrency and locking (ch5) seems to be a fairly difficult issue. It is in userspace (threading), seems to be even harder in kernel space imho.

5. First exam tomorrow, "Rights of Intellectual Property". Wish me luck ;-)

Ikke • Technology, Linux, Desktop, Coding Corner 2 comments

Been busy lately due to uni work, so not much hacking time. I did enhance that messaging thing a little (not working on other stuff I'd like to work on yet as they're potential SoC projects :-)).

wall, write and other pty based communication support still isn't in there as I didn't manage to get something working (yet). Must be doing something completely wrong somehow.

I did add a "Reply" option to the incoming messages though. Currently the reply dialog is not HIG at all, no I18N support, it's crap PyGTK code, but it does work somewhat.

Here's a little demo (1MB animated GIF screencast, thanks Byzanz (and Company)!)

I made a first "release" for people who's want to play with this. You can find the tarball here, but note it needs work: checking for Python stuff in configure.in, fixing Python code, adding I18N support, get the dialog code inside the C daemon, as using a helper is plain stupid (I use a helper as it's pretty easy to create a GUI using PyGTK quickly).

TODO: incoming message throttling (so one can't flood you using smbclient in a shell for loop), I18N (damn intltool 's been driving me crazy), nicer UI, other messaging "protocol" support, get a Telepathy backend out of this (jdub's idea),...

Ikke • Technology, Linux, Desktop, Coding Corner 11 comments

Davyd talked about integrating good old messaging systems like talk, wall, write and even WinPopup into the GNOME desktop. As it looked like a fun thing to do, I got my hands down on it today.

I still couldn't figure out how to catch wall and other pty-based messages, but I'm sure I will be able to get them working too.

At the moment, WinPopup messages work:

Maybe in-time one should be able to click the message popup and get a simple window allowing the user to reply on the incoming message, but thats to be done later on, first I want to get wall and talk requests working fine.

A little change to smb.conf is needed for this (the "message command" line should be set, I'm using a Python script to send the messages), and one file in the D-BUS system.d to allow the user Samba uses to spawn the message command ("nobody" on my system) to send messages on the system bus.
Obviously pty-based messages shouldn't need a callout anywhere.

Current code isn't ready for release yet (at all), I'll try to get what I got into good shape asap.

Ikke • Linux, Networks, Desktop, Coding Corner 6 comments