Date: Thu, 17 Mar 2016 15:51:35 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Jon Hunter <jonathanh@nvidia.com>
cc: Jason Cooper <jason@lakedaemon.net>, Marc Zyngier <marc.zyngier@arm.com>,
        =?ISO-8859-15?Q?Beno=EEt_Cousson?= <bcousson@baylibre.com>,
        Tony Lindgren <tony@atomide.com>, Rob Herring <robh+dt@kernel.org>,
        Pawel Moll <pawel.moll@arm.com>, Mark Rutland <mark.rutland@arm.com>,
        Ian Campbell <ijc+devicetree@hellion.org.uk>,
        Kumar Gala <galak@codeaurora.org>,
        Stephen Warren <swarren@wwwdotorg.org>,
        Thierry Reding <thierry.reding@gmail.com>,
        Kevin Hilman <khilman@kernel.org>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Grygorii Strashko <grygorii.strashko@ti.com>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Linus Walleij <linus.walleij@linaro.org>, linux-tegra@vger.kernel.org,
        linux-omap@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 04/15] irqchip/gic: WARN if setting the interrupt type
 fails
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On Thu, 17 Mar 2016, Jon Hunter wrote:

> Setting the interrupt type for private peripheral interrupts (PPIs) may
> not be supported by a given GIC because it is IMPLEMENTATION DEFINED
> whether this is allowed. There is no way to know if setting the type is
> supported for a given GIC and so the value written is read back to
> verify it matches the desired configuration. If it does not match then
> an error is return.
> 
> There are cases where the interrupt configuration read from firmware
> (such as a device-tree blob), has been incorrect and hence
> gic_configure_irq() has returned an error. This error has gone
> undetected because the error code returned was ignored but the interrupt
> still worked fine because the configuration for the interrupt could not
> be overwritten.
> 
> Given that this has done undetected and we should only fail to set the
> type for PPIs whose configuration cannot be changed anyway, don't return
> an error and simply WARN if this fails. This will allows us to fix up any
> places in the kernel where we should be checking the return status and
> maintain back compatibility with firmware images that may have incorrect
> interrupt configurations.

Though silently returning 0 is really the wrong thing to do. You can add the
warn, but why do you want to return success?

Thanks,

	tglx