linux-kernel - Re: [PATCH v5 3/6] irqchip: RISC-V per-HART local interrupt controller driver

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Date:   Fri, 29 May 2020 12:10:48 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Anup Patel <anup@...infault.org>
Cc:     Anup Patel <anup.patel@....com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Atish Patra <atish.patra@....com>,
        Alistair Francis <Alistair.Francis@....com>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 3/6] irqchip: RISC-V per-HART local interrupt
 controller driver

On 2020-05-29 11:45, Anup Patel wrote:
> On Fri, May 29, 2020 at 3:39 PM Marc Zyngier <maz@...nel.org> wrote:
>> 
>> On 2020-05-21 14:32, Anup Patel wrote:

[...]

>> > +/* Get the OF device node used by INTC irq domain */
>> > +struct device_node *riscv_of_intc_domain_node(void)
>> > +{
>> > +     return intc_domain_node;
>> > +}
>> > +EXPORT_SYMBOL_GPL(riscv_of_intc_domain_node);
>> 
>> Why do you need this? Why can't the timer node refer to its
>> interrupt-parent? The irqchip shouldn't be in the business of
>> working around DT issues.
>> 
>> At worse, use the default irqdomain if you must, but please
>> avoid this kind of construct.
> 
> Even, I don't like exporting riscv_of_intc_domain_node().
> 
> Thanks for your suggestion, I will certainly use the default irqdomain.

This should be a last resort solution. The irqdomain should
naturally come from the parent interrupt controller, accessible
from the device (the timer in this case) node.

Use it to for backward compatibility if you *really* must,
but this is generally a very bad idea as it allows all kind
of bizarre fallbacks and hides bugs.

Thanks,

          M.
-- 
Jazz is not dead. It just smells funny...