linux-kernel - Re: [PATCH v4] ata: pata_of_platform: Use platform_get_irq

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Date:   Wed, 5 Jan 2022 11:53:23 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Cc:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        Rob Herring <robh+dt@...nel.org>,
        Sergey Shtylyov <s.shtylyov@....ru>,
        Prabhakar <prabhakar.csengg@...il.com>,
        "open list:LIBATA SUBSYSTEM (Serial and Parallel ATA drivers)" 
        <linux-ide@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] ata: pata_of_platform: Use platform_get_irq_optional()
 to get the interrupt

On Wed, Jan 5, 2022 at 2:14 AM Lad Prabhakar
<prabhakar.mahadev-lad.rj@...renesas.com> wrote:
>
> platform_get_resource(pdev, IORESOURCE_IRQ, ..) relies on static
> allocation of IRQ resources in DT core code, this causes an issue
> when using hierarchical interrupt domains using "interrupts" property
> in the node as this bypasses the hierarchical setup and messes up the
> irq chaining.
>
> In preparation for removal of static setup of IRQ resource from DT core
> code use platform_get_irq_optional().
>
> Note this code just sets the start and not the end of IRQ resource as
> __pata_platform_probe() only uses the start member and also we don't
> set the IRQ resource flags as this is handled automatically for DT.

...

> +       irq = platform_get_irq_optional(ofdev, 0);
> +       if (irq < 0 && irq != -ENXIO)
> +               return irq;
> +
> +       if (irq > 0) {

> +               memset(&irq_res, 0, sizeof(irq_res));

To avoid subtle mistakes in the future, I would suggest doing this
unconditionally.

> +               irq_res.start = irq;

This is interesting. For consistency I would assign the end as well.

> +       }

Hence something like

memset(&irq_res, ...);

irq = ...
if (irq < 0 ...)
  return irq;
if (irq > 0) {
  irq_res.start = irq;
  irq_res.end = irq;
}

-- 
With Best Regards,
Andy Shevchenko