linux-kernel - Re: [PATCH v2] usb: Check !irq instead of irq == NO

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Date:   Thu, 10 Nov 2022 13:39:07 -0500
From:   Alan Stern <stern@...land.harvard.edu>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH v2] usb: Check !irq instead of irq == NO_IRQ

On Thu, Nov 10, 2022 at 06:54:35PM +0100, Christophe Leroy wrote:
> NO_IRQ is a relic from the old days. It is not used anymore in core
> functions. By the way, function irq_of_parse_and_map() returns value 0
> on error.
> 
> In some drivers, NO_IRQ is erroneously used to check the return of
> irq_of_parse_and_map().
> 
> It is not a real bug today because the only architectures using the
> drivers being fixed by this patch define NO_IRQ as 0, but there are
> architectures which define NO_IRQ as -1. If one day those
> architectures start using the non fixed drivers, there will be a
> problem.
> 
> Long time ago Linus advocated for not using NO_IRQ, see
> https://lkml.org/lkml/2005/11/21/221 . He re-iterated the same view
> recently in https://lkml.org/lkml/2022/10/12/622
> 
> So test !irq instead of tesing irq == NO_IRQ.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> ---
>  drivers/usb/host/ehci-grlib.c  | 2 +-
>  drivers/usb/host/ehci-ppc-of.c | 2 +-
>  drivers/usb/host/fhci-hcd.c    | 2 +-
>  drivers/usb/host/ohci-ppc-of.c | 2 +-
>  drivers/usb/host/uhci-grlib.c  | 2 +-
>  5 files changed, 5 insertions(+), 5 deletions(-)

For the [eou]hci-* files:

Acked-by: Alan Stern <stern@...land.harvard.edu>

Alan Stern