linux-kernel - Re: [PATCH v2 3/4] gpio: sifive: Get the parent IRQ's domain from its irq

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Date:   Wed, 19 Jul 2023 12:03:46 -0500
From:   Samuel Holland <samuel.holland@...ive.com>
To:     Andy Shevchenko <andy@...nel.org>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Emil Renner Berthing <emil.renner.berthing@...onical.com>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v2 3/4] gpio: sifive: Get the parent IRQ's domain from its
 irq_data

On 2023-07-19 11:54 AM, Andy Shevchenko wrote:
> On Wed, Jul 19, 2023 at 09:34:44AM -0700, Samuel Holland wrote:
>> Do not parse the devicetree again when the data is already available
>> from the IRQ subsystem. This follows the example of the ThunderX and
>> X-Gene GPIO drivers. The ngpio check is needed to avoid a possible
>> out-of-bounds read.
> 
> ...
> 
>> -	girq->parent_domain = parent;
>> +	girq->parent_domain = irq_get_irq_data(chip->irq_number[0])->domain;
> 
> For the sake of readability I would like to leave parent variable
> and assign it beforehand somewhere upper in the code.

OK.

> Also, can irq_get_irq_data() return NULL? Needs a comment on top
> of that assignment or an additional check.

No, the earlier loop already verified the IRQ number was valid. I don't think it
can later become invalid. In any case, we already dereference the result of
irq_get_irq_data(irq_number[foo]) in sifive_gpio_child_to_parent_hwirq().