linux-kernel - Re: [PATCH v2] [media] vb2: core: Lower the log level of debug outputs

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Date:   Thu, 8 Jun 2017 14:24:43 +0900
From:   Tomasz Figa <tfiga@...omium.org>
To:     Joe Perches <joe@...ches.com>
Cc:     Hirokazu Honda <hiroh@...omium.org>,
        Hans Verkuil <hverkuil@...all.nl>,
        Pawel Osciak <pawel@...iak.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] [media] vb2: core: Lower the log level of debug outputs

On Thu, Jun 8, 2017 at 2:16 PM, Joe Perches <joe@...ches.com> wrote:
> On Thu, 2017-06-08 at 13:39 +0900, Tomasz Figa wrote:
>> On Thu, Jun 8, 2017 at 12:24 PM, Hirokazu Honda <hiroh@...omium.org> wrote:
>> > Hi,
>> >
>> > I completely understand bitmask method now.
>> > I agree to the idea, but it is necessary to change the specification of
>> > a debug parameter.
>> >  (We probably need to change a document about that?)
>> > For example, there is maybe a user who set a debug parameter 3.
>> > The user assume that logs whose levels are less than 4 are shown.
>> > However, after the bitmask method is adopted, someday the logs whose
>> > level is 1 or 2 are only shown, not 3 level logs are not shown.
>> > This will be confusing to users.
>>
>> I think I have to agree with Hirokazu here. Even though it's only
>> about debugging, there might be some automatic testing systems that
>> actually rely on certain values here.
>
> I think it's a non-argument.
>
> If there automated systems that rely on specific levels, then
> changing the levels of individual messages could also cause
> those automated systems to fail.

Well, that might be true for some of them indeed. I was thinking about
our use case, which relies on particular numbers to get expected
verbosity levels not caring about particular messages. I guess the
break all or none rule is going to apply here, so we should do the
bitmap conversion indeed. :)

On the other hand, I think it would be still preferable to do the
conversion in a separate patch.

Best regards,
Tomasz