Re: [PATCH v4 1/4] genirq: define an empty function set_handle_irq() if !GENERIC_IRQ_MULTI_HANDLER

["Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>]

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@huawei.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.