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

[Marc Zyngier]

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@xxxxxxxxxx>
> > ---
> >  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.

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