Increasing the DMESG buffer....

Willem Jan Withagen wjw at
Sat Nov 24 23:19:28 UTC 2012

On 23-11-2012 1:20, Kevin Oberman wrote:
> On Thu, Nov 22, 2012 at 2:49 PM, Gary Palmer <gpalmer at> wrote:
>> On Thu, Nov 22, 2012 at 02:14:59PM -0800, Kevin Oberman wrote:
>>> On Thu, Nov 22, 2012 at 2:05 PM, Adrian Chadd <adrian at> wrote:
>>>> On 22 November 2012 06:30, Alexander Motin <mav at> wrote:
>>>>> Neither ICH, nor any other driver I know have amount of information
>>>>> comparable to what HDA hardware provides. So the analogy is not good.
>>>>> Respecting that most CODECs have no published datasheets, that information
>>>>> is the only input for debugging.
>>>>> snd_hda also uses hw.snd.verbose=3. But it is used for even deeper driver
>>>>> debugging. It also enables a lot of debugging in sound(4), that can be too
>>>>> verbose for HDA debugging.
>>>>> I will recheck again how can it be reorganized, but I think that the real
>>>>> problem is not in HDA. We need some way to structure and filter the output.
>>>> I honestly would like to just see it spat out using a userland tool,
>>>> rather than having the kernel print that level of topology data out.
>>>> It's highly unlikely that a topology problem is going to cause a
>>>> system to not boot, right? So the kernel itself doesn't need to be
>>>> able to spit that data out.
>>> Maybe I'm missing something, but the data needed to adjust HDAC is
>>> available from 'sysctl dev.hdaa'. I have not looked at the verbose
>>> output in quite a while, but I think it is mstly or entirely hte
>>> information in that and 'sysctl dev.hdac'. I never needed to look
>>> elsewhere to get mine set up properly.
>>> Also, isn't the entire verbose boot captured in /var/run/dmesg?
>> Only if the message buffer hasn't overflowed before the utility runs to
>> populate the file
> Ouch! I did miss hte obvious. Thanks for pointing this out.
> So we need to either expand the default buffer (not something I would
> want to do) or trim the verbosity of the verbose boot.
> Am I also missing an obvious reason most of the HDA output could not
> be eliminated since it is available y sysctl?

Reason I asked for how to set a bigger buffer was booting a serverboard
verbose.... And there is so much pci stuff dumped that it ran out of
space. Plenty of unknown devices.....

There is no sound on this board.

And usually that is the first thing that is asked for on this list, once
one start reporting problems.


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