Re: [PATCH v3 1/7] Documentation: dynamic-debug: Add description of level bitmask

From: Edward Cree <ecree@solarflare.com>
To: Joe Perches <joe@perches.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Stanimir Varbanov <stanimir.varbanov@linaro.org>
Cc: <linux-doc@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<linux-media@vger.kernel.org>, <linux-arm-msm@vger.kernel.org>,
	<linux-btrfs@vger.kernel.org>, <linux-acpi@vger.kernel.org>,
	<netdev@vger.kernel.org>, Jason Baron <jbaron@akamai.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Jim Cromie <jim.cromie@gmail.com>
Subject: Re: [PATCH v3 1/7] Documentation: dynamic-debug: Add description of level bitmask
Date: Tue, 9 Jun 2020 18:42:58 +0100	[thread overview]
Message-ID: <727b31a0-543b-3dc5-aa91-0d78dc77df9c@solarflare.com> (raw)
In-Reply-To: <ba32bfa93ac2e147c2e0d3a4724815a7bbf41c59.camel@perches.com>

On 09/06/2020 17:58, Joe Perches wrote:
> On Tue, 2020-06-09 at 13:16 +0200, Greg Kroah-Hartman wrote:
>> What is wrong with the existing control of dynamic
>> debug messages that you want to add another type of arbitrary grouping
>> to it? 
> There is no existing grouping mechanism.
>
> Many drivers and some subsystems used an internal one
> before dynamic debug.
>
> $ git grep "MODULE_PARM.*\bdebug\b"|wc -l
> 501
>
> This is an attempt to unify those homebrew mechanisms.
In network drivers, this is probablyusing the existing groupings
 defined by netif_level() - see NETIF_MSG_DRV and friends.  Note
 that those groups are orthogonal to the level, i.e. they control
 netif_err() etc. as well, not just debug messages.
Certainly in the case of sfc, and I'd imagine for many other net
 drivers too, the 'debug' modparam is setting the default for
 net_dev->msg_enable, which can be changed after probe with
 ethtool.
It doesn't look like the proposed mechanism subsumes that (we have
 rather more than 5 groups, and it's not clear how you'd connect
 it to the existing msg_enable (which uapi must be maintained); if
 you don't have a way to do this, better exclude drivers/net/ from
 your grep|wc because you won't be unifying those - in my tree
 that's 119 hits.

-ed