Re: [RFC PATCH 0/4] Drop custom logging - Greg Kroah-Hartman

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Phil Elwell <phil@raspberrypi.com>
Cc: Stefan Wahren <stefan.wahren@i2se.com>,
	Umang Jain <umang.jain@ideasonboard.com>,
	linux-media@vger.kernel.org, linux-staging@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org,
	linux-rpi-kernel@lists.infradead.org,
	Florian Fainelli <f.fainelli@gmail.com>,
	Adrien Thierry <athierry@redhat.com>,
	Dan Carpenter <error27@gmail.com>,
	Dave Stevenson <dave.stevenson@raspberrypi.com>,
	Kieran Bingham <kieran.bingham@ideasonboard.com>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 0/4] Drop custom logging
Date: Thu, 19 Jan 2023 14:37:45 +0100	[thread overview]
Message-ID: <Y8lHqd9FlxiXTLuW@kroah.com> (raw)
In-Reply-To: <CAMEGJJ1=dix7gWvV3Jxef-M-ExFZRTASQCr+6sn_dGsEQ=deYQ@mail.gmail.com>

On Thu, Jan 19, 2023 at 01:31:12PM +0000, Phil Elwell wrote:
> Hi all,
> 
> 
> On Wed, 18 Jan 2023 at 17:55, Stefan Wahren <stefan.wahren@i2se.com> wrote:
> >
> > Hi Umang,
> >
> > [add Phil]
> >
> > Am 18.01.23 um 12:58 schrieb Umang Jain:
> > > Drop custom logging from the vchiq interface.
> > > Mostly of them are replaced with dev_dbg and friends
> > > and/or pr_info and friends.
> > >
> > > The debugfs log levels (in 4/4) are mapped to kernel
> > > logs levels (coming from include/linux/kern_levels.h)
> > > Would like some thoughts on it as I am not sure (hence
> > > marking this is RFC)
> > >
> > >  From drivers/staging/vc04_services/interface/TODO:
> > >
> > > """
> > > * Cleanup logging mechanism
> > >
> > > The driver should probably be using the standard kernel logging mechanisms
> > > such as dev_info, dev_dbg, and friends.
> >
> > i don't have any experience with vchiq logging/debug. So i'm not sure if
> > it's acceptable to lose the second log level dimension (like
> > vchiq_arm_log_level) completely. Complex drivers like brcmfmac have a
> > debug mask to avoid log spamming [1]. Maybe this is a compromise.
> >
> > Btw some loglevel locations has already been messed up during
> > refactoring :-(
> >
> > [1] - drivers/net/wireless/broadcom/brcm80211/brcmfmac/debug.h
> >
> > > """
> > >
> > > Umang Jain (4):
> > >    staging: vc04_services: vchiq_core: Drop custom logging
> > >    staging: vc04_services: vchiq_arm: Drop custom logging
> > >    staging: vc04_services: Drop custom logging
> > >    staging: vc04_services: Drop remnants of custom logging
> > >
> > >   .../interface/vchiq_arm/vchiq_arm.c           | 151 +++---
> > >   .../interface/vchiq_arm/vchiq_connected.c     |   5 +-
> > >   .../interface/vchiq_arm/vchiq_core.c          | 479 ++++++++----------
> > >   .../interface/vchiq_arm/vchiq_core.h          |  39 --
> > >   .../interface/vchiq_arm/vchiq_debugfs.c       |  26 +-
> > >   .../interface/vchiq_arm/vchiq_dev.c           |  78 ++-
> > >   6 files changed, 329 insertions(+), 449 deletions(-)
> > >
> 
> Thanks for the nudge - this patch set hasn't yet made its way through
> the sluggish rpi-kernel moderation.
> 
> I understand the desire to remove the custom logging. I don't welcome
> the loss of flexibility that comes with such a strategy

What "loss of flexibility"?  You now have access to the full dynamic
debugging facilities that all of the rest of the kernel has.  What is
lacking?

> , but I'm not
> going to argue about it. What's harder to understand is the state that
> this patchset leaves VCHIQ logging in. From what I can see, the
> per-service logging control has gone, but the code still contains
> macros that hint at something useful. Similarly, the debugfs support
> is completely vestigial, giving the appearance of control while
> actually achieving nothing.

The debugfs files should also be removed if they don't do anything
anymore.

thanks,

greg k-h