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Subject: Re: [PATCH v1 0/19] drm/panel: drmP.h removal and DRM_DEV*
To:     Jani Nikula <jani.nikula@linux.intel.com>,
        Sam Ravnborg <sam@ravnborg.org>,
        Thierry Reding <thierry.reding@gmail.com>
Cc:     David Airlie <airlied@linux.ie>, Sean Paul <sean@poorly.run>,
        linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
        Stefan Mavrodiev <stefan@olimex.com>
From:   Andrzej Hajda <a.hajda@samsung.com>
Message-ID: <65d0b3cc-9d6b-737b-ded6-25d4174c16a8@samsung.com>
Date:   Fri, 1 Feb 2019 11:52:47 +0100
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        <20190131200723.GZ114153@art_vandelay> <20190131210312.GA8947@ravnborg.org>
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On 01.02.2019 11:30, Jani Nikula wrote:
> On Fri, 01 Feb 2019, Sam Ravnborg <sam@ravnborg.org> wrote:
>> Hi Thierry.
>>
>>> I personally like the DRM_DEV_* variants better because of the
>>> additional information that they provide. That can be useful when
>>> grepping logs etc.
>>>
>>> I'm slightly on the fence about this patch. The unwritten, and
>>> admittedly fuzzy, rules that I've been using so far are that dev_*() are
>>> used or messages that have to do with the panel device itself, whereas
>>> DRM_* variants are used for things that are actually related to DRM. So
>>> typically this would mean that roughly everything in ->probe() or
>>> ->remove() would be dev_*(), while the rest would be DRM_DEV_*().
>> For a rookie like me it is much simpler if one can use the same
>> logging primitives all over or at least the rules when to use what is simple.
>> It is simple to say that everything that exists below drivers/gpu/drm/
>> relates to drm.
>>
>> Suggested set of rules to follow:
>> - If in drm core, use DRM_XXX where XXX represent the core functionality
>> - If in a driver use DRM_DEV* if a struct device is available
>> - If in a driver and no struct device, use plain DRM_ERROR/INFO
> Core and drivers are already pretty conflated:
>
> http://patchwork.freedesktop.org/patch/msgid/20181227162310.13023-1-jani.nikula@intel.com
>
> ---
>
> Side note, I'd like to switch i915 to dev based debugs, but I absolutely
> hate the idea of changing:
>
> 	DRM_DEBUG_KMS("...")
>
> to:
>
> 	DRM_DEV_DEBUG_KMS(dev_priv->drm.dev, "...")
>
> I think the dev based macros are way too long, and would serve *most*
> (though not all) drivers better by having struct drm_device * rather
> than struct device * as the first param. In the above, just the
> boilerplate consumes half the line.
>
> Basically I'd like to see drm_ prefixed analogues to all the dev_ based
> logging functions, e.g. drm_dbg that takes drm_device. But it's so much
> churn that I'm contemplating just making i915 specific wrappers
> instead. :(


Does it means I am the only one who is not convinced to use all these
DRM_DEV helpers.

For me classic dev_(err|...) looks fine, if we really want to emphasize
that logs comes from DRM dev_* allows format modification, sth like this:

#define dev_fmt(fmt) "DRM: %s:%d: " fmt, __func__, __LINE__

but it is still something I do not see very helpful.


In general I think we have too many alternatives/flavours and developers
do not know what to choose, current usage of all these DRM_* shows it
clearly.


Regards

Andrzej


>
> BR,
> Jani.
>
>
>
>
>> If there is a need to distingush before/after one has a drm_device,
>> the best way would be to have a set of logging primitives that
>> take a drm_device. So we could extend the rule set:
>> - If in a driver use DRM_DRM* if a struct drm_device is available
>>   (This rule would take precedence over a struct device)
>>
>> DRM_DRM*, or DRM_DDEV* or ... But you get the idea.
>>
>> But this is not where we are today.
>>
>> Shall I redo the patch-set so we go back to dev_*() in probe() / remove()?
>>
>> 	Sam
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