linux-kernel - Re: [RFC PATCH v2 0/4] staging: vc04: Drop custom logging

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Date:   Sat, 23 Sep 2023 15:09:33 +0530
From:   Umang Jain <umang.jain@...asonboard.com>
To:     Stefan Wahren <stefan.wahren@...e.com>,
        Dan Carpenter <dan.carpenter@...aro.org>
Cc:     linux-staging@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org,
        linux-rpi-kernel@...ts.infradead.org, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Adrien Thierry <athierry@...hat.com>,
        Dan Carpenter <error27@...il.com>,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        Kieran Bingham <kieran.bingham@...asonboard.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Phil Elwell <phil@...pberrypi.com>
Subject: Re: [RFC PATCH v2 0/4] staging: vc04: Drop custom logging

Hi Stefan,

On 9/17/23 9:06 PM, Stefan Wahren wrote:
> Hi,
>
> Am 14.09.23 um 08:35 schrieb Dan Carpenter:
>> On Thu, Sep 14, 2023 at 12:25:24AM +0530, Umang Jain wrote:
>>> Hello,
>>>
>>> This series attempts to restart the discussion on custom logging used
>>> in VC04. In the last feedback gathered in [1] it seems that the logging
>>> would rather be moved to use dynamic debug. The series tries to move
>>> in that direction.
>>>
>>> The elephant in the room is the ability of turning on/off log levels,
>>> which this series just drops. Compensated by a crude strings
>>> ("error", "warning", "info"... etc) for easier grepping.
>>>
>>> The log category are also just strings (which probably can be 
>>> transformed
>>> to dynamic debug class names moving forwards?).
>>>
>>> To move forwards, I would like feedback on the broader direction.
>>> There are couple of TODOs in each of the patch (summarised in commit
>>> messages) which require case-by-case discussion.
>>>
>>> Additional high-level questions to move forwards:
>>> 1. Is loss of log levels by moving to dynamic debug, is actually a
>>>     concern? Is dynamic debug a valid replacement?
>>
>> Dynamic debug is honestly going to be an improvement.  I guess, Greg and
>> I said this back in Jan.

+1
>>
>>> 2. Whether debugfs should be dropped as well, found vestigial in [2]
>>
>> Yes. The "vchiq/log" should be removed.  Ideally as part of this
>> patchset so it's easier to understand.
>
> Yes, but please do not remote vchiq_debugfs entirely. I'm working on a 
> patch to move the state dump (debug feature) from the character device 
> /dev/vchiq to debugfs /sys/kernel/debug/vchiq/dump_state.

Can't the state dump be printed to dev_dbg() ? Will it pollute the 
kernel log?  Having debugfs for a single dump doesn't seem worthwhile if 
the state dump can be incorporated to dev_dbg() too.
>
>>
>>> 3. whether vchiq_log_trace() should actually be tracing support for 
>>> VC04
>>
>> That can be done later if people want.  No need to discuss it now.

Thanks Dan.
>>
>> regards,
>> dan carpenter
>>