netdev - Re: [PATCH 3/3] can: flexcan: handle S32G2/S32G3 separate interrupt lines

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Message-ID: <9dcc883c-0990-41b3-ae9e-eb1afdabeb65@oss.nxp.com>
Date: Tue, 19 Nov 2024 13:40:54 +0200
From: Ciprian Marian Costea <ciprianmarian.costea@....nxp.com>
To: Vincent Mailhol <mailhol.vincent@...adoo.fr>,
 Marc Kleine-Budde <mkl@...gutronix.de>, Andrew Lunn <andrew+netdev@...n.ch>,
 "David S . Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>
Cc: linux-can@...r.kernel.org, netdev@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 imx@...ts.linux.dev, NXP Linux Team <s32@....com>,
 Christophe Lizzi <clizzi@...hat.com>, Alberto Ruiz <aruizrui@...hat.com>,
 Enric Balletbo <eballetb@...hat.com>
Subject: Re: [PATCH 3/3] can: flexcan: handle S32G2/S32G3 separate interrupt
 lines

On 11/19/2024 1:36 PM, Vincent Mailhol wrote:
> On 19/11/2024 at 20:26, Vincent Mailhol wrote:
>> On 19/11/2024 at 19:01, Ciprian Marian Costea wrote:
>>> On 11/19/2024 11:26 AM, Vincent Mailhol wrote:
>>>> On 19/11/2024 at 17:10, Ciprian Costea wrote:
>>
>> (...)
>>
>>>>>    +    if (priv->devtype_data.quirks & FLEXCAN_QUIRK_SECONDARY_MB_IRQ) {
>>>>> +        err = request_irq(priv->irq_secondary_mb,
>>>>> +                  flexcan_irq, IRQF_SHARED, dev->name, dev);
>>>>> +        if (err)
>>>>> +            goto out_free_irq_err;
>>>>> +    }
>>>>
>>>> Is the logic here correct?
>>>>
>>>>     request_irq(priv->irq_err, flexcan_irq, IRQF_SHARED, dev->name, dev);
>>>>
>>>> is called only if the device has the FLEXCAN_QUIRK_NR_IRQ_3 quirk.
>>>>
>>>> So, if the device has the FLEXCAN_QUIRK_SECONDARY_MB_IRQ but not the
>>>> FLEXCAN_QUIRK_NR_IRQ_3, you may end up trying to free an irq which was
>>>> not initialized.
>>>>
>>>> Did you confirm if it is safe to call free_irq() on an uninitialized irq?
>>>>
>>>> (and I can see that currently there is no such device with
>>>> FLEXCAN_QUIRK_SECONDARY_MB_IRQ but without FLEXCAN_QUIRK_NR_IRQ_3, but
>>>> who knows if such device will be introduced in the future?)
>>>>
>>>
>>> Hello Vincent,
>>>
>>> Thanks for your review. Indeed this seems to be an incorrect logic since
>>> I do not want to create any dependency between 'FLEXCAN_QUIRK_NR_IRQ_3'
>>> and 'FLEXCAN_QUIRK_SECONDARY_MB_IRQ'.
>>>
>>> I will change the impacted section to:
>>>      if (err) {
>>>          if (priv->devtype_data.quirks & FLEXCAN_QUIRK_NR_IRQ_3)
>>>              goto out_free_irq_err;
>>>          else
>>>              goto out_free_irq;
>>>      }
>>
>> This is better. Alternatively, you could move the check into the label:
>>
>>    out_free_irq_err:
>>    	if (priv->devtype_data.quirks & FLEXCAN_QUIRK_NR_IRQ_3)
>>    		free_irq(priv->irq_err, dev);
>>
>> But this is not a strong preference, I let you pick the one which you
>> prefer.
> 
> On second thought, it is a strong preference. If you keep the
> 
> 	if (priv->devtype_data.quirks & FLEXCAN_QUIRK_NR_IRQ_3)
> 		goto out_free_irq_err;
> 	else
> 		goto out_free_irq;
> 
> then what if more code with a clean-up label is added to flexcan_open()?
> I am thinking of this:
> 
>    out_free_foo:
>    	free(foo);
>    out_free_irq_err:
>    	free_irq(priv-irq_err, dev);
>    out_free_irq_boff:
>    	free_irq(priv->irq_boff, dev);
> 
> Jumping to out_free_foo would now be incorrect because the
> out_free_irq_err label would also be visited.
> 

Correct, moving the check under the label would be better. Thanks.
I will change accordingly in V2.


Best Regards,
Ciprian

>>>>>        flexcan_chip_interrupts_enable(dev);
>>>>>          netif_start_queue(dev);
>>>>>          return 0;
>>>>>    + out_free_irq_err:
>>>>> +    free_irq(priv->irq_err, dev);
>>>>>     out_free_irq_boff:
>>>>>        free_irq(priv->irq_boff, dev);
>>>>>     out_free_irq:
>>
>> (...)
> 
> Yours sincerely,
> Vincent Mailhol
>