Re: [PATCH 06/14] [media] cx18: Use current logging styles

From: Andy Walls <awalls@md.metrocast.net>
To: Joe Perches <joe@perches.com>
Cc: Mauro Carvalho Chehab <mchehab@infradead.org>,
	ivtv-devel@ivtvdriver.org, linux-media@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 06/14] [media] cx18: Use current logging styles
Date: Sat, 27 Aug 2011 13:23:14 -0400	[thread overview]
Message-ID: <40a27a5f-f4ec-4304-88a1-a254c7bc6c68@email.android.com> (raw)
In-Reply-To: <1314463352.6852.5.camel@Joe-Laptop>

Joe Perches <joe@perches.com> wrote:

>On Sat, 2011-08-27 at 09:28 -0400, Andy Walls wrote:
>> On Wed, 2011-08-24 at 14:42 -0700, Joe Perches wrote:
>> > On Wed, 2011-08-24 at 06:34 -0400, Andy Walls wrote:
>> > > On Sun, 2011-08-21 at 15:56 -0700, Joe Perches wrote:
>> > > > Add pr_fmt.
>> > > > Convert printks to pr_<level>.
>> > > > Convert printks without KERN_<level> to appropriate pr_<level>.
>> > > > Removed embedded prefixes when pr_fmt was added.
>> > > > Use ##__VA_ARGS__ for variadic macros.
>> > > > Coalesce format strings.
>> > > 1. It is important to preserve the per-card prefixes emitted by
>the
>> > > driver: cx18-0, cx18-1, cx18-2, etc.  With a quick skim, I think
>your
>> > > change preserves the format of all output messages (except
>removing
>> > > periods).  Can you confirm this?
>> > Here's the output diff of
>> > strings built-in.o | grep "^<.>" | sort
>> > new and old
>[]
>> Yuck.
>> > > 2. PLease don't add a pr_fmt() #define to exevry file.  Just put
>one
>> > > where all the other CX18_*() macros are defined.  Every file
>picks those
>> > > up.
>> > It's not the first #include of every file.
>> > printk.h has a default #define pr_fmt(fmt) fmt
>> Well then don't use "pr_fmt(fmt)" in cx18, if it overloads a define
>> somewhere else in the kernel and has a dependency on its order
>relative
>> to #include statements.  That sort of thing just ups maintenance
>hours
>> later.  That's not a good trade off for subjectively better log
>> messages.
>> Won't redifining the 'pr_fmt(fmt)' generate preprocessor warnings
>> anyway?
>
>No.
>
>Andy, I fully understand how this stuff works.
>You apparently don't (yet).
>
>Look at include/linux/printk.h
>
>#ifndef pr_fmt
>#define pr_fmt(fmt) fmt
>#endif
>
>A default empty define is used when one
>is not specified before printk.h is
>included.  kernel.h includes printk.h
>
>v4l2_<level> uses the "name" of the video
>device in its output.  That name may not
>be the same name as the module.
>
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Hi Joe,

I don't need to fully understand it.

This is a happy to glad change with no functional nor performance benefit.  It adds unneeded lines of code to the driver and mangles some of the log messages.

I see no benefit from my perspective.

Regards,
Andy