snd-bt-sco built-in

Hi,

I'm trying to build snd-bt-sco directly into the kernel. Patched the kernel source a bit and it built ok. On bootup my kernel oopses:

snd-bt-sco revision 1.4 $

Unable to handle kernel NULL pointer dereference at virtual address 00000000
 printing eip:
c02b7f92
*pde = 00000000
Oops: 0000 [#1]
Modules linked in:
CPU:    0
EIP:    0060: [<C02B7F92>] Not tainted VLI
EFLAGS: 00010246    (2.6.10-mh4-sr1)

EIP is at snd_minor_search+0x12/0x50
eax: 00000000 ebx: c7e3a8e0 ecx: c7ffb160 edx: 00000000
esi: 00000000 edi: c7e3a802 ebp: c7fc7f38 esp: c7fc7eec
ds: 007b es: 007b ss: 0068
Process swapper (pid: 1, threadinfo: c7fc6000, task: c113f9e0)

Stack: c7e3a8e0 c7fc7f42 c02b8259 00000000 000000d0 00000000 380380c8 00000000
       00000000 c0434384 c7e30000 00000000 00000000 c02bce8d 00000000 
c7e30000
       00000000 c0434384 c7fc7f38 746e6f63 436c6f72 00000030 c04a2bb0 
c7e30000
Call Trace:
 [<c02b8259>] snd_register_device+0xc9/0x1a0
 [<c02bce8d>] snd_ctl_register+0x4d/0x70
 [<c02b8c70>] snd_card_free_thread+0x0/0x80
 [<c02b877a>] snd_card_new+0x19a/0x280
 [<c0498009>] snd_card_bt_sco_probe+0x29/0x260
 [<c0498267>] alsa_card_bt_sco_init+0x27/0x40
 [<c04788f3>] do_initcalls+0x23/0xc0
 [<c049a9f6>] sock_init+0x46/0x50
 [<c0100440>] init+0x0/0x120
 [<c010046a>] init+0x2a/0x120
 [<c0100858>] kernel_thread_helper+0x0/0x18
 [<c010085d>] kernel_thread_helper+0x5/0x18
Code: 20 3c c0 89 44 24 04 e9 ad e1 e6 ff 8d b6 00 00 00 00 8d bc 27 00 00 00 0

0 56 53 8b 74 24 0c 89 f0 c1 f8 05 8b 14 c5 a0 75 4c c0 <8b> 0a 8b 74 26 00 8d 04 c5 a0 75 4c c0 39 c2 74 22 89 c3 8d 74
<0>Kernel panic - not syncing: Attempted to kill init!

Digging through the source I found this in sound/core/sound.c:
...
static snd_minor_t *snd_minor_search(int minor)

{
	struct list_head *list;
	snd_minor_t *mptr;

	list_for_each(list, &snd_minors_hash[SNDRV_MINOR_CARD(minor)]) {
		mptr = list_entry(list, snd_minor_t, list);
		if (mptr->number == minor)
			return mptr;
	}
	return NULL;
}

...

To find out what's going wrong I added some debug messages:
...

	printk(KERN_INFO "snd_minors_hash: minor: %d\n", minor);
	list_for_each(list, &snd_minors_hash[SNDRV_MINOR_CARD(minor)]) {
		printk(KERN_INFO "snd_minors_hash: list_for_each\n");

...

The kernel oopses the same way:
...
snd-bt-sco revision 1.4 $
snd_minors_hash: minor: 0

Unable to handle kernel NULL pointer dereference at virtual address 00000000

...

As other soundcard drivers can be built in I think this is no problem with the kernel or ALSA-core.
Can someone please point me to why this is happening or is it known that snd-bt-sco is working as module only?
Thanks in advance.

Best regards,
Sebastian

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-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Sebastian Roth wrote:

| Hi,
|
| I'm trying to build snd-bt-sco directly into the kernel.

why?

| As other soundcard drivers can be built in I think this is no problem
| with the kernel or ALSA-core.
| Can someone please point me to why this is happening or is it known
| that snd-bt-sco is working as module only?

I think nobody ever tried to compile it into the kernel, and I definitly never did. I think it's not written with that in mind.

I can't tell for sure why this function is failing this way. Did you build snd-hw-dep and put it in the kernel, too? If it's missing than that could be the problem. I think the dynamic loader would notice in a module, but propably not if the kernel itself is missing it.

best regards,
~ Lars

|
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- --
Lars Grunewaldt
* software development
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web: http://www.dark-reality.de
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Hi Lars,

thanks for your fast reply!

I'm working on a project in which a "communication-server" should use bluetooth headsets...
So I want to have the kernel with all functions built-in. If this is not possible I'll have to load it on startup. ;-(

That was my first guess too! But it's built-in

grep SND /boot/config-2.6.10-mh4-sr1 | grep -v "^#" CONFIG_SND=y
CONFIG_SND_TIMER=y
CONFIG_SND_PCM=y
CONFIG_SND_HWDEP=y
CONFIG_SND_RAWMIDI=y
CONFIG_SND_SEQUENCER=y
CONFIG_SND_OSSEMUL=y
CONFIG_SND_MIXER_OSS=y
CONFIG_SND_PCM_OSS=y CONFIG_SND_SEQUENCER_OSS=y CONFIG_SND_RTCTIMER=m CONFIG_SND_AC97_CODEC=y CONFIG_SND_EMU10K1=y
CONFIG_SND_USB_AUDIO=y
CONFIG_SND_BT_SCO=y

Best regards,
Sebastian

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Hi,

I found the problem! To built it into the kernel I added a directory under sound called bluetooth. Getting the make-system to compile the module you have to add this path to sound/Makefile:

cat /usr/src/linux/sound/Makefile
...
obj-$(CONFIG_SND) += bluetooth/ core/ i2c/ drivers/ isa/ pci/ ppc/ arm/ synth/ usb/ sparc/ parisc/ pcmcia/
...

Really don't know why but I've put it in the first position (before core). This leads to the problem that on bootup ALSA isn't initialized yet when snd_bt_sco is trying to use it. oops...

cat /usr/src/linux/sound/Makefile #(correct one!)
...
obj-$(CONFIG_SND) += core/ i2c/ drivers/ isa/ pci/ ppc/ arm/ synth/ usb/ sparc/ parisc/ pcmcia/ bluetooth/
...

Now the kernel boots up! A brief test with one of the headsets was ok!

Best regards,
Sebastian

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