Messages in this thread | | | Date | Thu, 17 Sep 2015 22:13:31 +0100 | From | Russell King - ARM Linux <> | Subject | Re: [PATCH 1/3] clocksource: rockchip: Make the driver more readability and compatible |
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On Thu, Sep 17, 2015 at 12:57:53PM +0200, Daniel Lezcano wrote: > Hi Thomas, > > there is one thing I don't understand. > > If the IRQ0 is invalid, irq_of_parse_and_map returning zero means an error > and from what you said it is ok. > > But I see the NO_IRQ on ARM is (-1) and the drivers are checking with NO_IRQ > the return code of irq_of_parse_and_map. So if there is an error, that won't > be detected.
NO_IRQ being -1 is a legacy thing for ARM - all ARM drivers are supposed to be converted to use <= 0 or == 0 to detect invalid IRQs, and _eventually_ once all users are gone, NO_IRQ deleted.
Moreover, there are supposed to be no _new_ users of NO_IRQ ever added to the kernel.
Modern drivers should _all_ be using !irq to detect invalid IRQs, and not using NO_IRQ.
The steps here are:
1. Convert all ARM platforms to start numbering IRQs from 1 rather than 0. 2. Convert all drivers used on ARM to detect lack of IRQ by checking for <= 0. 3. Replace NO_IRQ assignments with zero-initialisations. 4. Remove NO_IRQ.
The reason it hasn't happened is that it requires effort and testing, and rather than running around getting old platforms to boot (which includes remembering _how_ to get them to boot) with recent kernels, I prefer to spend my time doing more productive work with modern code.
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