Increasing the DMESG buffer....

Kevin Oberman kob6558 at
Fri Nov 23 00:20:55 UTC 2012

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?
R. Kevin Oberman, Network Engineer
E-mail: kob6558 at

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