Re: [Cocci] [PATCH v5 0/3] Add error message to platform_get_irq*()

From: Stephen Boyd <swboyd@chromium.org>
To: Wolfram Sang <wsa@the-dreams.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Rob Herring <robh@kernel.org>,
	Michal Marek <michal.lkml@markovi.net>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
	Nicolas Palix <nicolas.palix@imag.fr>,
	linux-kernel@vger.kernel.org,
	Javier Martinez Canillas <javierm@redhat.com>,
	Andrzej Hajda <a.hajda@samsung.com>,
	Andy Shevchenko <andy.shevchenko@gmail.com>,
	Mark Brown <broonie@kernel.org>,
	Russell King - ARM Linux <linux@armlinux.org.uk>,
	cocci@systeme.lip6.fr,
	Marek Szyprowski <m.szyprowski@samsung.com>
Subject: Re: [Cocci] [PATCH v5 0/3] Add error message to platform_get_irq*()
Date: Wed, 31 Jul 2019 07:52:27 -0700	[thread overview]
Message-ID: <5d41ab2c.1c69fb81.6129.661f@mx.google.com> (raw)
In-Reply-To: <20190731142645.GA1680@kunai>

Quoting Wolfram Sang (2019-07-31 07:26:46)
> Hi Stephen,
> 
> > There were some comments about adding an 'optional' platform_get_irq()
> > API in v4. This series doesn't include that, but I can add such an API
> > if it's required. I started to look into how it might work and got hung
> > up on what an optional IRQ means. I suppose it means that in DT there
> > isn't an 'interrupts' property in the device node, but in ACPI based
> > firmware I'm not sure what that would correspond to. Furthermore, the
> > return value is hard to comprehend. Do we return an error when an
> > optional irq can't be found? It doesn't seem safe to return 0 because
> > sometimes 0 is a valid IRQ. Do other errors in parsing the IRQ
> > constitute a failure when the IRQ is optional?
> 
> Some time ago, I tried a series like yours and got stuck at this very
> point. I found drivers where using an interrupt was optional and
> platform_get_irq() returning a failure wasn't fatal. The drivers used
> PIO then or dropped some additional functionality. Some of them were
> very old.
> 
> I didn't like the idea that platform_get_irq() will spit out errors for
> those drivers, yet I couldn't create a suitable cocci-script to convert
> drivers to use the *_optional callback where possible. So, I neither
> created the optional callback.
> 
> I still have doubts of unneeded error messages popping up. Has this been
> discussed already? (Sorry, I missed the first iterations of this series)

Not heavily discussed, but it was mentioned in an earlier round. If
these drivers pop up, I think we can have another function like
platform_get_irq_probe() or platform_get_irq_nowarn() that doesn't print
an error message. Then we can convert the drivers that are poking around
for interrupts to use this new function instead. It isn't the same as a
platform_get_optional_irq() API because it returns an error when the irq
isn't there or we fail to parse something, but at least the error
message is gone.