linux-kernel - Re: [PATCH] pata_of_platform: fix no irq handling

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Date:	Mon, 06 Oct 2008 15:41:19 -0500
From:	Matt Sealey <matt@...esi-usa.com>
To:	avorontsov@...mvista.com
CC:	Jeff Garzik <jgarzik@...ox.com>, linuxppc-dev@...abs.org,
	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org,
	Li Yang <leoli@...escale.com>, Wang Jian <lark@...ux.net.cn>
Subject: Re: [PATCH] pata_of_platform: fix no irq handling

There is a simple problem with the patch which is that an "IRQ 0" can and does
actually exist on a bunch of platforms, at least to the best of my knowledge.

Checking for -1 (which means for definite, no irq at all, because it is
totally unambiguous, as a -1 IRQ numbering is "impossible") is more correct.

The problem is the check against an unsigned value for interrupts (is there
any reason why you would need 4 billion interrupts possible instead of just
2 billion?) although I must say, the patch will work, and probably 99.9999999%
of people will never see a problem with it :)

-- 
Matt Sealey <matt@...esi-usa.com>
Genesi, Manager, Developer Relations

Anton Vorontsov wrote:
> When no irq specified the pata_of_platform fills the irq_res with -1,
> which is wrong to do for two reasons:
> 
> 1. By definition, 'no irq' should be IRQ 0, not some negative integer;
> 2. pata_platform checks for irq_res.start > 0, but since irq_res.start
>    is unsigned type, the check will be true for `-1'.
> 
> Reported-by: Steven A. Falco <sfalco@...ris.com>
> Signed-off-by: Anton Vorontsov <avorontsov@...mvista.com>
> ---
> 
> Resending again...
> 
>  drivers/ata/pata_of_platform.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/ata/pata_of_platform.c b/drivers/ata/pata_of_platform.c
> index 408da30..1f18ad9 100644
> --- a/drivers/ata/pata_of_platform.c
> +++ b/drivers/ata/pata_of_platform.c
> @@ -52,7 +52,7 @@ static int __devinit pata_of_platform_probe(struct of_device *ofdev,
>  
>  	ret = of_irq_to_resource(dn, 0, &irq_res);
>  	if (ret == NO_IRQ)
> -		irq_res.start = irq_res.end = -1;
> +		irq_res.start = irq_res.end = 0;
>  	else
>  		irq_res.flags = 0;
>  
--
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