[PATCH 1/3] clocksource: rockchip: Make the driver more readability and compatible

Russell King - ARM Linux linux at arm.linux.org.uk
Thu Sep 17 14:13:31 PDT 2015

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.

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