linux-kernel - Re: [PATCH] platform: finally disallow IRQ0 in platform_get

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Date:   Fri, 26 Nov 2021 17:20:34 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Sergey Shtylyov <s.shtylyov@....ru>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] platform: finally disallow IRQ0 in platform_get_irq()
 and its ilk

On Sat, Nov 06, 2021 at 11:26:47PM +0300, Sergey Shtylyov wrote:
> 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@....ru>
> 
> ---
> The patch is against the 'driver-core-linus' branch of Greg Kroah-Hartman's
> 'driver-core.git' repo.
> 
>  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;

You need to get approval from the interrrupt developers for this type of
change, as it is a change and might break existing platforms, right?

thanks,

greg k-h