Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [PATCH v3 5/5] tty/serial: Add Spreadtrum sc9836-uart driver support | Date | Thu, 27 Nov 2014 16:36:52 +0100 |
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On Thursday 27 November 2014 23:23:17 Lyra Zhang wrote: > > Yes, I saw this way in other serial drivers. > But, if then, there are two questions for me: > 1. Why did some serial drivers need an UN_SHARED irq?
A lot of drivers were written before we had shared IRQs, or were copied from old drivers, or are for hardware that uses edge-triggered interrupts instead of level-triggered interrupts.
Only level-triggered interrupts can be shared.
> 2. How can we choose a right way?
It never hurts to implement a shared interrupt handler. Only if you have no way to find out whether the device triggered the interrupt or not you have to leave out IRQF_SHARED, and then you won't be able to return IRQ_NONE.
Arnd
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