linux-kernel - Re: [PATCH v4 1/4] genirq: define an empty function set_handle_irq() if !GENERIC_IRQ_MULTI

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Date:   Thu, 17 Sep 2020 17:47:34 +0800
From:   "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
To:     Marc Zyngier <maz@...nel.org>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Rob Herring <robh+dt@...nel.org>, Guo Ren <guoren@...nel.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-csky <linux-csky@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Haoyu Lv <lvhaoyu@...wei.com>, Libin <huawei.libin@...wei.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        "Jianguo Chen" <chenjianguo3@...wei.com>
Subject: Re: [PATCH v4 1/4] genirq: define an empty function set_handle_irq()
 if !GENERIC_IRQ_MULTI_HANDLER



On 2020/9/17 17:32, Marc Zyngier wrote:
> On 2020-09-17 04:46, Leizhen (ThunderTown) wrote:
>> On 2020/9/15 16:43, Zhen Lei wrote:
>>> To avoid compilation error if an irqchip driver references the function
>>> set_handle_irq() but may not select GENERIC_IRQ_MULTI_HANDLER on some
>>> systems.
>>
>> Hi, Marc:
>>   Do you agree with this method?
>>
>>   Otherwise, I should use "#ifdef CONFIG_GENERIC_IRQ_MULTI_HANDLER ... #endif"
>> to perform the compilation isolation. This may make the code less beautiful.
>>
>>>
>>> For example, the Synopsys DesignWare APB interrupt controller
>>> (dw_apb_ictl) is used as the secondary interrupt controller on arc, csky,
>>> arm64, and most arm32 SoCs, and it's also used as the primary interrupt
>>> controller on Hisilicon SD5203 (an arm32 SoC). The latter need to use
>>> set_handle_irq() to register the top-level IRQ handler, but this multi
>>> irq handler registration mechanism is not implemented on arc system.
>>>
>>> The input parameter "handle_irq" maybe defined as static and only
>>> set_handle_irq() references it. This will trigger "defined but not used"
>>> warning. So add "(void)handle_irq" to suppress it.
>>>
>>> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
>>> ---
>>>  include/linux/irq.h | 2 ++
>>>  1 file changed, 2 insertions(+)
>>>
>>> diff --git a/include/linux/irq.h b/include/linux/irq.h
>>> index 1b7f4dfee35b397..0848a2aaa9b40b1 100644
>>> --- a/include/linux/irq.h
>>> +++ b/include/linux/irq.h
>>> @@ -1252,6 +1252,8 @@ void irq_matrix_free(struct irq_matrix *m, unsigned int cpu,
>>>   * top-level IRQ handler.
>>>   */
>>>  extern void (*handle_arch_irq)(struct pt_regs *) __ro_after_init;
>>> +#else
>>> +#define set_handle_irq(handle_irq)    do { (void)handle_irq; } while (0)
>>>  #endif
>>>
>>>  #endif /* _LINUX_IRQ_H */
>>>
> 
> You shouldn't just make it a NOP. Consider adding a WARN_ON(1), so that
> people can realize this cannot work without the required architecture support.

Oh, right. I will add it.

> 
>         M.