problems in /proc read and alsamixer

problems in /proc read and alsamixer

[Prince John]

Hi,
I'm working on an Alsa driver for a Hitachi SH4 based
board with an AC'97 codec (AD1881).
ALSA driver - Ver. 0.9.1
Linux kernel - Ver. 2.4.18

All the modules are getting loadedand AC'97 read/write
call backs are working fine. 
But I'm facing following problems:

Problem 1: Segmentation Fault while reading the AC97
proc entries. 

/proc/asound/card0 directory contents:

# ls -l /proc/asound/card0
-r--r--r--    1 root     root            0 Jun  7
16:10 Aspen18xx
-r--r--r--    1 root     root            0 Jun  7
16:10 ac97#0
-r--r--r--    1 root     root            0 Jun  7
16:10 ac97#0regs
-r--r--r--    1 root     root            0 Jun  7
16:22 id
dr-xr-xr-x    3 root     root            0 Jun  7
16:22 pcm0c
dr-xr-xr-x    3 root     root            0 Jun  7
16:22 pcm0p
--------------

Following error comes when I try to read the ac97#0
files:

# cat ac97#0

Unable to handle kernel NULL pointer dereference at
virtual address 00000000
pc = 8c11091e
*pde = 00000000
Oops: 0000

PC  : 8c11091e SP  : 8c47dc10 SR  : 40000100 TEA :
c0100034    Not tainted
R0  : 00000002 R1  : 00000000 R2  : 0000007e R3  :
c014c685
R4  : 0000000a R5  : ffffffff R6  : c014c684 R7  :
ffffffff
R8  : 8cd75df4 R9  : 8c47dc60 R10 : 00000000 R11 :
ffffffff
R12 : 00000002 R13 : 8c47de5f R14 : 8c47dc60
MACH: 000004bf MACL: 00000000 GBR : ff800000 PR  :
c01022be
-------------------

# cat Aspen18xx

 Fault in unaligned fixup: 0000
-------------------

Similar types of errors are coming while reading other
proc files (in this dir) too. I think the error
happens
during the snd_iprintf function calls in ac97_codec.c
file, but don't know how to resolve it. Has anybody
face this problem?
Any ideas to resolve it?


Problem 2:
I have cross compiled the alsa utilities for my target
(SH4 based). While executing (in super user mode)
'alsamixer', it terminates with following
error message:

ALSA lib control.c:612:<snd_ctl_open_noupdate> Invalid
CTL default
alsamixer: function snd_ctl_open failed for default:

In mailing list, I could see many queries on this
error, but couldn't find any proper solution for this.
The snddevices script was run before this, which
creates the relevant device under /dev

Could you please give some advices to resolve these
issues?

Thanks a lot,
Prince.

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Re: problems in /proc read and alsamixer

[Takashi Iwai]

At Wed, 25 Jun 2003 07:38:26 -0700 (PDT),
Prince John wrote:
> 
> Hi,
> I'm working on an Alsa driver for a Hitachi SH4 based
> board with an AC'97 codec (AD1881).
> ALSA driver - Ver. 0.9.1
> Linux kernel - Ver. 2.4.18
> 
> All the modules are getting loadedand AC'97 read/write
> call backs are working fine. 
> But I'm facing following problems:
> 
> Problem 1: Segmentation Fault while reading the AC97
> proc entries. 
> 
> /proc/asound/card0 directory contents:
> 
> # ls -l /proc/asound/card0
> -r--r--r--    1 root     root            0 Jun  7
> 16:10 Aspen18xx
> -r--r--r--    1 root     root            0 Jun  7
> 16:10 ac97#0
> -r--r--r--    1 root     root            0 Jun  7
> 16:10 ac97#0regs
> -r--r--r--    1 root     root            0 Jun  7
> 16:22 id
> dr-xr-xr-x    3 root     root            0 Jun  7
> 16:22 pcm0c
> dr-xr-xr-x    3 root     root            0 Jun  7
> 16:22 pcm0p
> --------------
> 
> Following error comes when I try to read the ac97#0
> files:
> 
> # cat ac97#0
> 
> Unable to handle kernel NULL pointer dereference at
> virtual address 00000000
> pc = 8c11091e
> *pde = 00000000
> Oops: 0000
> 
> PC  : 8c11091e SP  : 8c47dc10 SR  : 40000100 TEA :
> c0100034    Not tainted
> R0  : 00000002 R1  : 00000000 R2  : 0000007e R3  :
> c014c685
> R4  : 0000000a R5  : ffffffff R6  : c014c684 R7  :
> ffffffff
> R8  : 8cd75df4 R9  : 8c47dc60 R10 : 00000000 R11 :
> ffffffff
> R12 : 00000002 R13 : 8c47de5f R14 : 8c47dc60
> MACH: 000004bf MACL: 00000000 GBR : ff800000 PR  :
> c01022be
> -------------------
> 
> # cat Aspen18xx
> 
>  Fault in unaligned fixup: 0000
> -------------------
> 
> Similar types of errors are coming while reading other
> proc files (in this dir) too. I think the error
> happens
> during the snd_iprintf function calls in ac97_codec.c
> file, but don't know how to resolve it. Has anybody
> face this problem?
> Any ideas to resolve it?

this kind of problem has appeared when different gcc versions were
used for the kernel and the ALSA modules.  not sure whether it's your
case.  the problem #2 also seems like the behavior happening with the
gcc-mismatch above.

can SH4 trace oops via ksymoops?


Takashi


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Re: problems in /proc read and alsamixer

[Prince John]

>Has anybody face this problem?
> > Any ideas to resolve it?
> 
> this kind of problem has appeared when different gcc
> versions were
> used for the kernel and the ALSA modules.  not sure
> whether it's your
> case.  the problem #2 also seems like the behavior
> happening with the
> gcc-mismatch above.
> 
>  
> Takashi
-------------
Hi Takashi,
Thank you verymuch for your response.
I'm using sh4-linux-gcc ver 3.0.4 for both Kernel and
ALSA driver, lib and utils. I'm using ALSA driver -
Ver. 0.9.1. Will it help if I change to the latest
version?

> can SH4 trace oops via ksymoops?

Sorry, I didn't get it. Could u please clarify it?

Thanks,
Prince



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Re: problems in /proc read and alsamixer

[Takashi Iwai]

At Tue, 1 Jul 2003 06:00:35 -0700 (PDT),
Prince John wrote:
> 
> >Has anybody face this problem?
> > > Any ideas to resolve it?
> > 
> > this kind of problem has appeared when different gcc
> > versions were
> > used for the kernel and the ALSA modules.  not sure
> > whether it's your
> > case.  the problem #2 also seems like the behavior
> > happening with the
> > gcc-mismatch above.
> > 
> >  
> > Takashi
> -------------
> Hi Takashi,
> Thank you verymuch for your response.
> I'm using sh4-linux-gcc ver 3.0.4 for both Kernel and
> ALSA driver, lib and utils. I'm using ALSA driver -
> Ver. 0.9.1. Will it help if I change to the latest
> version?

hmm, so that's not the case.

about upgrading, yes, it's better to use the latest version.
it will also make it easier to integrate your code into our tree.


> > can SH4 trace oops via ksymoops?
> 
> Sorry, I didn't get it. Could u please clarify it?

on intel (and many other) architectures, we can trace the stack
printed to the kernel message via ksymoops program when a kernel oops
happens.  i have no idea about SH4 development environment, but if you
have such one, this will help greatly to spot the buggy point out.


Takashi


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