RE: [Questions]: how to extend nr_irqs for arch arm64
From: Zhou Qiao(周侨)
Date: Mon Jan 11 2016 - 04:05:10 EST
> -----Original Message-----
> From: Thomas Gleixner [mailto:tglx@xxxxxxxxxxxxx]
> Sent: Monday, January 11, 2016 4:51 PM
> To: Zhou Qiao(周侨)
> Cc: jason@xxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: RE: [Questions]: how to extend nr_irqs for arch arm64
> On Mon, 11 Jan 2016, Zhou Qiao(周侨) wrote:
> > I met an issue here. The nr_irqs is extended when the start_irq + cnt
> > > nr_irqs. So when nr_irqs is not extended(still 64), a device with a
> > large
> > hr_irq(70) will get a wrong virq. since it will be mod by nr_irqs
> > before
> No, it won't get a wrong virq. It will get a virq and it does not
> matter at all whether the hardware irq number is 10, 70, 500 or 5000.
> What's your problem?
Let's assume the hw_irq is 70, and after the mod operation, it will call irq_alloc_descs_from with parameter from = 6, instead of 70. So the newly allocated descriptor is mapped to hw_irq = 6, not 70. Later when driver registers irq with irq = 70, it will fail since there is no irq descriptor for irq = 70.