linux-kernel - Re: [PATCH 1/1] Add documentation for proper usage and order of preference of calls to print diagnostic messages.

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Date:	Tue, 4 Mar 2014 14:39:42 +0100
From:	Levente Kurusa <levex@...ux.com>
To:	yogesh <mr.yogesh@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, Joe Perches <joe@...ches.com>
Subject: Re: [PATCH 1/1] Add documentation for proper usage and order of
 preference of calls to print diagnostic messages.

Hi,

2014-03-04 12:48 GMT+01:00 yogesh <mr.yogesh@...il.com>:
> This patch adds documentation that clarifies the use of various diagnostic printing messages. It shows the preference of subsystem_dbg calls to dev_dbg (whenever possible), as the first preferred format of logging debug messages.

Please wrap your changelog at 80 characters a line.

> Signed-off-by: Yogesh Chaudhari <mr.yogesh@...il.com>
> ---
>  Documentation/CodingStyle | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/Documentation/CodingStyle b/Documentation/CodingStyle
> index 7fe0546..9e0de25 100644
> --- a/Documentation/CodingStyle
> +++ b/Documentation/CodingStyle
> @@ -662,6 +662,20 @@ and driver, and are tagged with the right level:  dev_err(), dev_warn(),
>  dev_info(), and so forth.  For messages that aren't associated with a
>  particular device, <linux/printk.h> defines pr_debug() and pr_info().
>
> +If the subsystem has its own diagnostic macros then they should be used
> +instead of dev_dbg calls.
> +e.g. If you are using network subsystem, use netdev_dbg;
> +if you are using V4L, use v4l_dbg etc.
> +This standardises the output format in every subsystem.
> +
> +Depending on your changes, the following order of precedence
> +applies to printing messages:
> +1. [subsystem]_dbg() is preferred when you the

The 'you' is unnecessary and incorrect.

> +subsystem has its own diagnostic macros.
> +2. dev_dbg() is preferred when you have a generic struct device object.
> +3. pr_debug() is used when 1 and 2 above are not applicable.

I think it's better to say "should be used".

> +4. printk() should be avoided.
> +
>  Coming up with good debugging messages can be quite a challenge; and once
>  you have them, they can be a huge help for remote troubleshooting.  Such
>  messages should be compiled out when the DEBUG symbol is not defined (that

I think we should also mention *_warn, *_err etc not just *_dbg.

--
Regards,
Levente Kurusa
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