linux-kernel - Re: [PATCH 0/4] drm: core: Convert logging to drm

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Message-ID: <20200712185416.GC12262@blackclown>
Date:   Mon, 13 Jul 2020 00:24:16 +0530
From:   Suraj Upadhyay <usuraj35@...il.com>
To:     Joe Perches <joe@...ches.com>, sam@...nborg.org,
        maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
        tzimmermann@...e.de, airlied@...ux.ie, daniel@...ll.ch
Cc:     linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 0/4] drm: core: Convert logging to drm_* functions.

On Sat, Jul 11, 2020 at 11:16:33AM -0700, Joe Perches wrote:
> On Sat, 2020-07-11 at 20:41 +0530, Suraj Upadhyay wrote:
> > On Fri, Jul 10, 2020 at 07:56:43PM +0200, Sam Ravnborg wrote:
> > > Hi Suraj.
> > > 
> > > On Tue, Jul 07, 2020 at 10:04:14PM +0530, Suraj Upadhyay wrote:
> > > > This patchset converts logging to drm_* functions in drm core.
> > > > 
> > > > The following functions have been converted to their respective
> > > > DRM alternatives :
> > > > dev_info()      --> drm_info()
> > > > dev_err()       --> drm_err()
> > > > dev_warn()      --> drm_warn()
> > > > dev_err_once()  --> drm_err_once().
> > > 
> > > I would prefer that DRM_* logging in the same files are converted in the
> > > same patch. So we have one logging conversion patch for each file you
> > > touches and that we do not need to re-vist the files later to change
> > > another set of logging functions.
> > 
> > Agreed.
> > 
> > > If possible WARN_* should also be converted to drm_WARN_*
> > > If patch is too large, then split them up but again lets have all
> > > logging updated when we touch a file.
> > > 
> > > Care to take a look at this approach?
> > > 
> > 
> > Hii,
> > 	The problem with WARN_* macros is that they are used without any
> > drm device context. For example [this use here](https://cgit.freedesktop.org/drm/drm-misc/tree/drivers/gpu/drm/drm_edid.c#n1667) in drm_edid.c,
> > doesn't have a drm device context and only has one argument (namely !raw_edid).
> > There are many more such use cases.
> > 
> > And also there were cases where dev_* logging functions didn't have any
> > drm_device context.
> 
> Perhaps change the __drm_printk macro to not
> dereference the drm argument when NULL.
> 
> A trivial but perhaps inefficient way might be
> used like:
> 
> 	drm_<level>(NULL, fmt, ...)
> 
> ---
>  include/drm/drm_print.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/drm/drm_print.h b/include/drm/drm_print.h
> index 1c9417430d08..9323a8f46b3c 100644
> --- a/include/drm/drm_print.h
> +++ b/include/drm/drm_print.h
> @@ -395,8 +395,8 @@ void drm_dev_dbg(const struct device *dev, enum drm_debug_category category,
>  
>  /* Helper for struct drm_device based logging. */
>  #define __drm_printk(drm, level, type, fmt, ...)			\
> -	dev_##level##type((drm)->dev, "[drm] " fmt, ##__VA_ARGS__)
> -
> +	dev_##level##type((drm) ? (drm)->dev : NULL, "[drm] " fmt,	\
> +			  ##__VA_ARGS__)
>  
>  #define drm_info(drm, fmt, ...)					\
>  	__drm_printk((drm), info,, fmt, ##__VA_ARGS__)
> 

Hi Joe,
	Thanks for your input.
But I don't think that this change would be a good idea as we are
supposed to find or make a substitute of WARN_* macros which
take a `condition` as an argument and check for its truth.
And I guess passing a NULL to dev_<level> would cause a format warning.

Also, the WARN_* macros are doing their job fine, and passing a NULL
value everytime you want to warn about a certain condition at a
particular line, doesn't seem good to me.

Thus, I think that WARN_* macros should be untouched.

I would like to hear what the MAINTAINERS think.

Thanks and Cheers,

Suraj Upadhyay.


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