linux-kernel - Re: [PATCH v8 7/8] net-next: mvpp2: relax return value check for IRQ get

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Message-ID: <ee0341fc-b621-b7c0-4312-be2ad3c29da6@gmail.com>
Date:   Tue, 1 Aug 2023 15:44:16 +0300
From:   Matti Vaittinen <mazziesaccount@...il.com>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        Marcin Wojtas <mw@...ihalf.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 7/8] net-next: mvpp2: relax return value check for IRQ
 get

On 8/1/23 15:31, Russell King (Oracle) wrote:
> On Tue, Aug 01, 2023 at 03:04:24PM +0300, Matti Vaittinen wrote:
>> fwnode_irq_get[_byname]() were changed to not return 0 anymore.
>>
>> Drop check for return value 0.
>>
>> Signed-off-by: Matti Vaittinen <mazziesaccount@...il.com>
> 
> Sorry, but I don't think you've properly considered the effects of your
> patch.

Don't be sorry.

> 
>> @@ -5833,7 +5833,7 @@ static int mvpp2_multi_queue_vectors_init(struct mvpp2_port *port,
>>   			v->irq = of_irq_get_byname(port_node, irqname);
>>   		else
>>   			v->irq = fwnode_irq_get(port->fwnode, i);
>> -		if (v->irq <= 0) {
>> +		if (v->irq < 0) {
> 
> You're making this change based on the assumption that fwnode_irq_get()
> has changed its return values, but I really don't think you've looked
> at the code and considered the return value behaviour of the DT function
> above. Reading it's documentation, it states that of_irq_get_byname()
> may return 0 on IRQ mapping failure.

You're correct. Thanks for spotting this! Seems like I really overlooked 
the behaviour of the of_irq_get_byname().

> So, by making this change, you are allowing IRQ mapping failure in the
> DT path to succeed rather than fail.
> 
>>   			ret = -EINVAL;
>>   			goto err;
>>   		}
>> @@ -6764,7 +6764,7 @@ static int mvpp2_port_probe(struct platform_device *pdev,
>>   		err = -EPROBE_DEFER;
>>   		goto err_deinit_qvecs;
>>   	}
>> -	if (port->port_irq <= 0)
>> +	if (port->port_irq < 0)
> 
> Exactly the same problem here, but...
> 
>>   		/* the link irq is optional */
>>   		port->port_irq = 0;
> 
> this is less critical... but still wrong.
> 
> So, given that this patch is basically incorrect...
> 
> NAK.
> 

-- 
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland

~~ When things go utterly wrong vim users can always type :help! ~~