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From: Saravana Kannan <saravanak@google.com>
To: Rob Herring <robh+dt@kernel.org>
Cc: Andrew Lunn <andrew@lunn.ch>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	John Stultz <john.stultz@linaro.org>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Vladimir Oltean <olteanv@gmail.com>,
	Android Kernel Team <kernel-team@android.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v1 5/5] driver core: Add fw_devlink.debug command line boolean parameter
Date: Tue, 14 Sep 2021 10:31:30 -0700	[thread overview]
Message-ID: <CAGETcx9TN-sLdcir5kChNjx4i+C7gpyTSq4C+EARt42FmP_LzQ@mail.gmail.com> (raw)
In-Reply-To: <CAL_Jsq+D2nyzrvWE7vdbQFB680+cmx=FfFMqHL0s=tkTSduz2Q@mail.gmail.com>

On Tue, Sep 14, 2021 at 9:52 AM Rob Herring <robh+dt@kernel.org> wrote:
>
> On Tue, Sep 14, 2021 at 11:44 AM Andrew Lunn <andrew@lunn.ch> wrote:
> >
> > > I did think of this, but the problem is that dynamic debug logs can
> > > get compiled out (when DYNAMIC_DEBUG isn't set). I think debugging of
> > > fw_devlink needs to be possible without having to recompile the
> > > kernel. So in a sense similar to how initcall_debug works today.
> >
> > My off the shelf Debian kernel has it enabled. Maybe you can check
> > other mainline distributions and see if it is enabled by default.
>
> Right, I would expect users that can't rebuild their kernel easily
> would have it enabled.
>
> > You are also on a slippery path. You argue this is needed all the time
> > and add a custom knob. Somebody else adds a new feature which they
> > also argue always needs bug, and add there own custom knob. We soon
> > have lots of custom knobs, each doing it slightly differently, in
> > different places. Chaos. So you need a really good argument why your
> > code really is special.
> >
> > I would suggest you start with dynamic debug, and collect some
> > statistics of how often you need to ask people to recompile their
> > kernel.
>
> I agree.

Fair enough -- Andrew/Rob.

>
> What would be nice is documenting what needs to be set for devlink.
> What I used was just 'dyndbg="file drivers/base/core.c +p"'

Yeah, I was thinking if we went with dynamic debug I'd have something
I'll copy paste as a reply to any fw_devlink debug email thread.

Where would be a good place to document this?

I was actually thinking of making fw_devlink.debug=1 be an alias for
something like:
dyndbg="func device_link_add +p; func device_links_check_suppliers +p"....

So that people don't have to remember what to copy paste into their
command line as things change.

-Saravana

      reply	other threads:[~2021-09-14 17:32 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-14  4:39 [PATCH v1 0/5] fw_devlink improvements Saravana Kannan
2021-09-14  4:39 ` [PATCH v1 1/5] driver core: fw_devlink: Improve handling of cyclic dependencies Saravana Kannan
2021-09-14  6:16   ` Marek Szyprowski
2021-09-14  8:01     ` Saravana Kannan
2021-09-14 12:35   ` Rob Herring
2021-09-14 16:23     ` Saravana Kannan
2021-09-14  4:39 ` [PATCH v1 2/5] driver core: Set deferred probe reason when deferred by driver core Saravana Kannan
2021-09-14  7:01   ` Geert Uytterhoeven
2021-09-14  7:58     ` Saravana Kannan
2021-09-15  5:41       ` Saravana Kannan
2021-09-14  4:39 ` [PATCH v1 3/5] driver core: Create __fwnode_link_del() helper function Saravana Kannan
2021-09-14  7:04   ` Geert Uytterhoeven
2021-09-14  7:46     ` Saravana Kannan
2021-09-14  4:39 ` [PATCH v1 4/5] driver core: Add debug logs when fwnode links are added/deleted Saravana Kannan
2021-09-14  7:09   ` Geert Uytterhoeven
2021-09-14  4:39 ` [PATCH v1 5/5] driver core: Add fw_devlink.debug command line boolean parameter Saravana Kannan
2021-09-14 15:10   ` Andrew Lunn
2021-09-14 16:27     ` Saravana Kannan
2021-09-14 16:43       ` Andrew Lunn
2021-09-14 16:52         ` Rob Herring
2021-09-14 17:31           ` Saravana Kannan [this message]

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