linux-kernel - Re: [PATCH] i2c: s3c2410: Properly handle interrupts of number 0

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Message-ID: <20180302162821.bmsxgrqqaginjooo@lakrids.cambridge.arm.com>
Date:   Fri, 2 Mar 2018 16:28:21 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Russell King - ARM Linux <linux@...linux.org.uk>
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        linux-samsung-soc@...r.kernel.org,
        Wolfram Sang <wsa@...-dreams.de>, linux-kernel@...r.kernel.org,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Kukjin Kim <kgene@...nel.org>, linux-i2c@...r.kernel.org,
        Ben Dooks <ben-linux@...ff.org>, stable@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] i2c: s3c2410: Properly handle interrupts of number 0

On Fri, Mar 02, 2018 at 03:32:22PM +0000, Russell King - ARM Linux wrote:
> How do we break this status quo and finally solve the IRQ 0 and
> NO_IRQ issue?

> Another possibility would be to change platform_get_irq() and
> suffer the regressions that will cause, telling people that fixing
> their platform IRQ numbering is the only solution (but this
> requires breaking our ideals about regressions.)

How about we start with a warning? That'll be visible, but shouldn't
result in broken systems while we wait for people to fix things up.

e.g. something like the below.

Mark.

---->8----
diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index f1bf7b38d91c..bd42eeffd2aa 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -126,7 +126,12 @@ int platform_get_irq(struct platform_device *dev, unsigned int num)
                irqd_set_trigger_type(irqd, r->flags & IORESOURCE_BITS);
        }
 
-       return r ? r->start : -ENXIO;
+       if (!r)
+               return -ENXIO;
+
+       WARN_ONCE(!r->start, "Platform uses zero as a valid IRQ.");
+
+       return r->start;
 #endif
 }
 EXPORT_SYMBOL_GPL(platform_get_irq);