netdev - Re: [PATCH] soc: qcom: ipa: Remove superfluous error message around platform_get

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Date:   Fri, 11 Jun 2021 11:04:19 +0800
From:   Zhongjun Tan <hbut_tan@....com>
To:     Alex Elder <elder@...e.org>
Cc:     David Miller <davem@...emloft.net>, elder@...nel.org,
        kuba@...nel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, tanzhongjun@...ong.com
Subject: Re: [PATCH] soc: qcom: ipa: Remove superfluous error message around
 platform_get_irq()

On Thu, 10 Jun 2021 16:38:43 -0500
Alex Elder <elder@...e.org> wrote:

> On 6/10/21 4:11 PM, David Miller wrote:
> > From:  Zhongjun Tan <hbut_tan@....com>
> > Date: Thu, 10 Jun 2021 22:01:18 +0800
> >   
> >> diff --git a/drivers/net/ipa/ipa_smp2p.c
> >> b/drivers/net/ipa/ipa_smp2p.c index 34b68dc43886..93270e50b6b3
> >> 100644 --- a/drivers/net/ipa/ipa_smp2p.c
> >> +++ b/drivers/net/ipa/ipa_smp2p.c
> >> @@ -177,11 +177,8 @@ static int ipa_smp2p_irq_init(struct
> >> ipa_smp2p *smp2p, const char *name, int ret;
> >>   
> >>   	ret = platform_get_irq_byname(smp2p->ipa->pdev, name);
> >> -	if (ret <= 0) {
> >> -		dev_err(dev, "DT error %d getting \"%s\" IRQ
> >> property\n",
> >> -			ret, name);
> >> +	if (ret <= 0)  
> > Applied, but this code still rejects an irq of zero which is a
> > valid irq number.  
> 
> It rejects IRQ 0 intentionally.  And if 0 is returned, there
> will now be no message printed by the platform code.
> 
> As I recall, I looked for a *long* time to see whether IRQ 0
> was a valid IRQ number in Linux.  One reason I even questioned
> it is that NO_IRQ is defined with value 0 on some architectures
> (though not for Arm).  I even asked Rob Herring about privately
> it a few years back and he suggested I shouldn't allow 0.
> 
> Yes, it *looked* like IRQ 0 could be a valid return.  But I
> decided it was safer to just reject it, on the assumption
> that it's unlikely to be returned (I don't believe it is
> or ever will be used as the IRQ for SMP2P).
> 
> If you are certain it's valid, and should be allowed, I
> have no objection to changing that "<=" to be "<".
> 
> 					-Alex
> 
> PS  A quick search found this oldie:
>        https://yarchive.net/comp/linux/no_irq.html

I think so , It is better to change "<=" to be "<".