[PATCH v2] platform: finally disallow IRQ0 in platform_get_irq() and its ilk

[Sergey Shtylyov <s.shtylyov@omp.ru>]

The commit a85a6c86c25b ("driver core: platform: Clarify that IRQ 0 is
invalid") only calls WARN() when IRQ0 is about to be returned, however
using IRQ0 is considered invalid (according to Linus) outside the arch/
code where it's used by the i8253 drivers. Many driver subsystems treat
0 specially (e.g. as an indication of the polling mode by libata), so
the users of platform_get_irq[_byname]() in them would have to filter
out IRQ0 explicitly and this (quite obviously) doesn't scale...
Let's finally get this straight and return -EINVAL instead of IRQ0!

Fixes: a85a6c86c25b ("driver core: platform: Clarify that IRQ 0 is invalid")
Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Acked-by: Marc Zyngier <maz@kernel.org>

---
The patch is against the 'driver-core-next' branch of Greg Kroah-Hartman's
'driver-core.git' repo.

Changes in version 2:
- added Marc's ACK.

 drivers/base/platform.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Index: driver-core/drivers/base/platform.c
===================================================================
--- driver-core.orig/drivers/base/platform.c
+++ driver-core/drivers/base/platform.c
@@ -231,7 +231,8 @@ int platform_get_irq_optional(struct pla
 out_not_found:
 	ret = -ENXIO;
 out:
-	WARN(ret == 0, "0 is an invalid IRQ number\n");
+	if (WARN(!ret, "0 is an invalid IRQ number\n"))
+		return -EINVAL;
 	return ret;
 }
 EXPORT_SYMBOL_GPL(platform_get_irq_optional);
@@ -446,7 +447,8 @@ static int __platform_get_irq_byname(str
 
 	r = platform_get_resource_byname(dev, IORESOURCE_IRQ, name);
 	if (r) {
-		WARN(r->start == 0, "0 is an invalid IRQ number\n");
+		if (WARN(!r->start, "0 is an invalid IRQ number\n"))
+			return -EINVAL;
 		return r->start;
 	}