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. -- FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.
