[alsa-devel] softvol plug-in dependancies?
Hi Guys
The softvol plug-in, are there any pre-requisites or dependancies to using this? I've tried various entries in the /etc/asound.conf configuration file all with the same result.
I can see the control in alsamixer, once I've run the speaker-test through it, but cannot adjust any settings. Trying to run 'alsactl store 0' results in this error :
. alsactl: control.c:2437: snd_ctl_elem_value_get_integer: Assertion `idx < sizeof (obj->value.integer.value) / sizeof(obj->value.integer.value[0])' failed. Aborted .
Curiously using amixer the device is listed but its properties are displayed like this
. Simple mixer control 'PCM Vol',0 Capabilities: volume Playback channels: Front Left - Front Right - Rear Left - Rear Right - Front C enter - Woofer - Side Left - Side Right - Rear Center - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? Capture channels: Front Left - Front Right - Rear Left - Rear Right - Front Ce nter - Woofer - Side Left - Side Right - Rear Center - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? - ? Limits: 0 - 0 Front Left: 0 [0%] Front Right: 0 [0%] Rear Left: 0 [0%] Rear Right: 0 [0%] Front Center: 0 [0%] Woofer: 0 [0%] Side Left: 0 [0%] Side Right: 0 [0%] Rear Center: 0 [0%] ?: 0 [0%] ?: 0 [0%] ?: 0 [0%] ?: 0 [0%] ?: 0 [0%] ?: 0 [0%] ?: 0 [0%] ?: 0 [0%] ?: 0 [0%] ?: 0 [0%] ?: 0 [0%] ?: 0 [0%] ?: 0 [0%] ?: 0 [0%] ?: 0 [0%] ?: 0 [0%] ?: 0 [0%] ?: 0 [0%] ?: 0 [0%] ?: 0 [0%] ?: 0 [0%] ?: 0 [0%] ?: 0 [0%]
Any clues as to what's going on here would be much appreciated before I have to start dissecting the library.
TIA for any hints Simon
At Sat, 10 May 2008 20:59:28 +0100, Simon Dunn wrote:
Hi Guys
The softvol plug-in, are there any pre-requisites or dependancies to using this?
No, AFAIK.
I've tried various entries in the /etc/asound.conf configuration file all with the same result.
I can see the control in alsamixer, once I've run the speaker-test through it, but cannot adjust any settings. Trying to run 'alsactl store 0' results in this error :
. alsactl: control.c:2437: snd_ctl_elem_value_get_integer: Assertion `idx < sizeof (obj->value.integer.value) / sizeof(obj->value.integer.value[0])' failed. Aborted .
Which ALSA version, which driver and how is your configuration setup? The softvol itself is known to work in most cases, but of course, there could be remaining bugs. But, I suspect it's rather specific to your use-case...
Takashi
Which ALSA version, which driver and how is your configuration setup? The softvol itself is known to work in most cases, but of course, there could be remaining bugs. But, I suspect it's rather specific to your use-case...
Hi Takashi,
Thanks for your reply.
The version of ALSA lib and utils I'm mainly using is 1.0.10, though I've tried version 1.0.16 and get the same results.
The Linux kernel I'm using is version 2.6.10, which includes the ALSA driver architecture version 1.0.6.
I'm running this on a freescale mcf5475, Coldfire based platform.
I've reverted to using the dummy driver and a very basic asound.conf file, see below, but still no joy with the plug-in.
It's the output from running amixer, once the softvol control is enabled, that I find most curious. Listing its contents just seems to produce an uninitialised device. Given the big endian nature of the cpu I'm suspicious that this may be an endian bug, though after spending a couple of days examining the alsa-lib code I've failed to find anything wrong up to now, obviously ;)
Has the softvol plug-in been used on a big endian system to your knowledge?
Running amixer shows the controls implemented in the Dummy driver perfectly well, and these can be adjusted using amixer or alsamixer.
The DMIX plug-in works just fine so if it is a bug, endian or otherwise, then it is probably limited to the softvol plug-in rather than alsa-lib in general.
Any help or suggestions you can provide is greatly appreciated.
Regards Simon
. asound.conf .
pcm.globalvol { type softvol slave.pcm "hw:0,0" control.name "GLOBAL Vol" control.card 0 }
Hi Takashi et al
Just thought I'd let you know that I found the bug that was causing the softvol plug-in to fail. As usual my suspicions were about as far from the cause as it is possible to get; it was neither a bug in the user mode code, nor was it an endian issue.
I found the culprit in the core module in the kernel code. As I said in earlier mails the kernel version I'm using (2.6.10) is not the latest and contains the 1.0.6 version of the ALSA drivers.
The latest driver code I've looked at (1.0.15) already has fixes applied and is not vulnerable to the same bug so I'm not reporting anything new.
I'll put a brief synopsis of the bug at the end of this email if anyone's interested, otherwise you can stop reading now.
Takashi, thanks for your input.
Best regards Simon
Description -----------
I found the bug in the kernel core module in sound/core/control.c. It was a 2 fold issue;
1) The elem_data pointer member of the user_element struct was being assigned an address 4 bytes into the user_element struct instead of at the end of it.
Change the statement .. ue->elem_data = (char *)ue + sizeof(ue) + dimen_size; to .. ue->elem_data = (char *)ue + sizeof(*ue) + dimen_size;
fixes that one.
2) The softvol control is now enumerated correctly but still does not work; amixer and alsamixer both report the volume as zero and neither can modify it. The reason for this is that the user_element struct is not holding information pertaining to the min and max volumes levels permitted by the control. This information is passed into the driver via the _info parameter of snd_ctl_elem_add but was not being retained.
To fix it is a simple matter of retaining all the information provided by snd_ctl_elem_add and returning it appropriately.
As I said both of these issues are accounted for in latter versions of the driver code so this description of them is for information only, should someone else trip over the same bug when using older versions of the architecture.
~Simon
participants (2)
-
Simon Dunn -
Takashi Iwai