quoted

So people can compile with -Werror (RT patchset).

Why do you mention the RT patch set here? Doesn't the vanila tree gets
compiled with -Werror as well?

Not for me.

quoted

irq_chip *irqchip = NULL; /* pet old compilers */

That would probably work, too. I would drop that comment but then
someone might clean that up :P

Yup. But I just remembered a better solution:

From: Wolfram Sang <redacted>
Subject: [PATCH] ppc: mpc52xx: silence false positive from old GCC

So people can compile with -Werror.

Signed-off-by: Wolfram Sang <redacted>
---
 arch/powerpc/platforms/52xx/mpc52xx_pic.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/52xx/mpc52xx_pic.c b/arch/powerpc/platforms/52xx/mpc52xx_pic.c
index b89ef65..2898b73 100644
--- a/arch/powerpc/platforms/52xx/mpc52xx_pic.c
+++ b/arch/powerpc/platforms/52xx/mpc52xx_pic.c

@@ -340,7 +340,7 @@ static int mpc52xx_irqhost_map(struct irq_domain *h, unsigned int virq,
 {
 	int l1irq;
 	int l2irq;
-	struct irq_chip *irqchip;
+	struct irq_chip *uninitialized_var(irqchip);
 	void *hndlr;
 	int type;
 	u32 reg;

uninitialized_var was created for exactly that purpose IIRC.

quoted

People not realizing 'default' is a no-op might wonder why unknown 
levels are mapped to critical.

I see. And what would you suggest as default in case we would have an
additional bit?

-Esome or a different error message. But let's postpone that until that
case happens ;)

Hmmm. I assumed that critical / SDMA / … are interrupt numbers but they
are seem not be. In that case I guess l2 is more important. l1 kinda
looks important since it is the value in the switch case which failed
but since it can only hold one possible value, I guess your info is
better :)

Thanks,

   Wolfram