I decided to switch my desktop computer to another distro. After about 5 years with the same Debian Sid install, I switched to Manjaro. Manjaro use the same base system as Arch Linux but seems to be more user friendly.

Anyway, the hibernate don’t work out-of-the-box. When you restart the computer, it doesn’t restore the hibernate image from the swap. You can fix that quickly. Edit /etc/mkinitcpio.conf file and add “resume” to the HOOK flag like this.

HOOKS="base udev autodetect modconf block resume filesystems keyboard fsck"

After that, you must rebuild the initcpio file :

 sudo mkinitcpio -p linux39

That’s enough, you can now test with a simple pm-hibernate.

/Enjoy Linux again.

In fact, if you use Jackd (and perhaps Pulse) you can change the sound card used by Spotify, but this is overkill for my needs (mainly cause, I use Spotify on a litte old netbook and Jackd is a nightmare to configure)

After some strace dump, Alsa (libasound2) source reading, I decided to fix it by myself. Let’s go for some Monkey Patching. Monkey patching on closed source binary isn’t that easy, the hard step : find the right function to hack. Here the Alsa tutorial come to rescue (ldd of course too). So we need to modify the snd_pcm_open call.

Let’s give it a try : First we need to dynamically re-route this call to a wrapper. The easier way to do this, is to build a special library and to force Spotify to use the wrapper with an LD_PRELOAD hack. (see code below). In fact, Spotify call the snd_pcm_open with name=”default” which is the default sound card, so we can change this to “usb” for example, and fix the .asoundrc to point “usb” sound card to the right hardware card.

That’s enough, let’s code :

#define _GNU_SOURCE

#include <dlfcn.h>
#include <stdio.h>
#include <alsa/asoundlib.h>

static int (*wrap_snd_pcm_open)(snd_pcm_t **pcm, const char *name, snd_pcm_stream_t stream, int mode) = NULL;

void * wrap(void * func,char *name)
{
    char *msg;
    if (func == NULL) {
        func = dlsym(RTLD_NEXT, name);
        fprintf(stderr, "** wrapping %s =>  %p\n", name,func);
        if ((msg = dlerror()) != NULL) {
            fprintf(stderr, "** %s: dlopen failed : %s\n", name,msg);
            exit(1);
        } else {
            fprintf(stderr, "** %s: wrapping done\n",name);
        }
    }
    return func;
}

int snd_pcm_open(snd_pcm_t **pcm, const char *name, snd_pcm_stream_t stream, int mode)
{
    int temp;

    sprintf(name,"usb");

    wrap_snd_pcm_open = wrap(wrap_snd_pcm_open,"snd_pcm_open");
    temp = wrap_snd_pcm_open(pcm,name,stream,mode);
    fprintf(stderr, "** Calling snd_pcm_open for path:[%s] => fd:[%d]\n",name,temp);
    fflush(stderr);
    return temp;

}

As you can see in the code, I use a generic wrapper function because during my code session, I used this function to re-route some other functions. To build the library :

gcc -g -fPIC -shared -Wl,-soname,preload.so -ldl -o preload.so  main.c

Load the lib, with export LD_PRELOAD=./preload.so before running Spotify. Spotify (and all other software using Alsa) will use “usb” as default sound card.

Note: C reader will note that name is a const char pointer, and so we can’t change it, but even if gcc raise a big warning, the code do trick fine.

Enjoy good quality sound even w/ closed source

That’s fine, but I’m unable to debug this part of the code because I’m unable to place a breakpoint. So I want to place a “break” in my code that’s return back to GDB. (exactly like you can launch the debugger within Python w/ a simple pdb.set_trace().

This is quite easy to do, and really useful but not really popular. The main trick is to call the interrupt number 3. This will rise a SIGTRAP signal in the Linux kernel that GDB can intercept .. so in your code simply add a macro :

#define GDB()  asm("int $0x3")
int main()
{
 int a = 12;
 GDB();
 printf("A ==> %u \n",a);
 return 0;   
}

Call the GDB(); macro in your code, compile it with gcc -g, simply run your program in GDB, and wait for the macro to be called :)

/Enjoy gdb

Anyway, sometime ago the HAL was introduced in Xorg. This allow you to hotplug mouse / keyboard … But if for a reason, your HAL is buggy .. you can’t use a keyboard or a mice in Xorg. That’s a bullshit ! I discover a bug in RAID + HAL, and HAL is now segfaulting on my computer .. so I need to get ride of this Xorg / HAL …

First you must modify /etc/X11/Xorg.conf with something like this :

Section "ServerFlags"
    Option "AutoAddDevices" "False"
    Option "AllowEmptyInput" "False"
EndSection

This disable the hal support, but if you want to have the keyboard and mice, you must install the following packages :

• xserver-xorg-input-kbd
• xserver-xorg-input-mouse

That’s it… no HAL support Xorg anymore, that works fine …

This is an old trick, but udev added a little complexity, so let’s give it a try. First boot on a Ubunty CD, open a console and run:

(here my linux partition is sda2, second partition on a sata disk)

mkdir /media/mnt
mount /dev/sda2 /media/mnt/
mount -o bind /dev/ /media/mnt/dev
chroot /media/mnt

=> now you are on the destination disk, so you can install grub.
grub-install /dev/sda

Of course you can do a lot more stuff, like changing fstab etc etc .. but the trick is to mount + mount bind + chroot

Fine, except that I’m unable to get hardware openGL working and Google Earth is
really slow, so I decided to fix that. (done on two computers..)

agpgart: Detected 892K stolen memory.
agpgart: AGP aperture is 128M @ 0xf0000000
[drm] Initialized drm 1.0.1 20051102
...
[drm] Initialized i915 1.4.0 20060119 on minor 0
[drm] Initialized i915 1.4.0 20060119 on minor 1

sudo apt-get install xserver-xorg

(II) I810(0): [drm] created "i915" driver at busid "pci:0000:00:02.0"
(II) I810(0): [drm] added 8192 byte SAREA at 0xe0b2f000

display: :0  screen: 0
direct rendering: Yes
server glx vendor string: SGI
server glx version string: 1.2

ps aux|gawk '$11 == "ssh" {print $2}'

apt-get install grub
grub-install /dev/hdXX #where to put the bootloader

Now you can reboot. But to have a nice menu edit a file /boot/grub/menu.lst like that:

default=0
timeout=5
boot=/dev/hda

title Linux-2.6.7
root (hd0,1)
kernel /boot/vmlinuz-2.6.7 root=/dev/hda2 vga=791 ro

title Debian-2.4
root (hd0,1)
kernel /boot/vmlinuz-2.4.26-1-686-smp ro root=/dev/hda2
initrd=/boot/initrd.img-2.4.26-1-686-smp

title Memtest
root (hd0,1)
kernel /boot/memtest86+.bin

Note: My boot is hda2 (hd0,1) second partition of the first disk

This is pretty kool since, this kind of stuff can be usefull. I think about:

• security of course ( using Additional directive )
• or usefull ( for example in POS …)

Anyway i will install this on my notebook since I use it a lot and I can’t always trust the potential users. ( I usually leave it w/ xlock at my work. )