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

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Message-ID: <CAO5uPHOX=++z_YGFoCapH9fvhPwXpC5xr=gCCimAK=ZJ5pp7Hw@mail.gmail.com>
Date:   Thu, 8 Jun 2017 12:24:16 +0900
From:   Hirokazu Honda <hiroh@...omium.org>
To:     Hans Verkuil <hverkuil@...all.nl>
Cc:     Joe Perches <joe@...ches.com>, 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
Subject: Re: [PATCH v2] [media] vb2: core: Lower the log level of debug outputs

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.
The function that users can select a log method is necessary (e.g.
implement dprintk_bitmask and dprintk_level)

The main purpose of my patch is to not output much log messages.
I think the current patch is enough to accomplish the purpose.

Changing the method is a related but different task from my patch.
Therefore, I think it should be done in another patch.

Best,
Hirokazu Honda

On Wed, Jun 7, 2017 at 6:01 PM, Hans Verkuil <hverkuil@...all.nl> wrote:
> On 31/05/17 06:06, Joe Perches wrote:
>> On Wed, 2017-05-31 at 12:28 +0900, Hirokazu Honda wrote:
>>> If I understand a bitmap correctly, it is necessary to change the log level
>>> for each message.
>>> I didn't mean a bitmap will take a long CPU time.
>>> I mean the work to change so takes a long time.
>>
>> No, none of the messages or levels need change,
>> only the >= test changes to & so that for instance,
>> level 1 and level 3 messages could be emitted
>> without also emitting level 2 messages.
>>
>> The patch suggested is all that would be required.
>>
>
> I prefer the solution that Joe proposed as well.
>
> It's more useful, esp. with a complex beast like vb2.
>
> Regards,
>
>         Hans