Re: Why isn't IRQ shared for i2c-ocore

[Lee Jones <lee.jones@linaro.org>]

On Fri, 08 May 2015, Geert Uytterhoeven wrote:

> On Thu, May 7, 2015 at 9:01 AM, Lee Jones <lee.jones@linaro.org> wrote:
> >> I have a follow up question regarding interrupt. I see many I2C bus drivers
> >> request interrupt with flag = 0. Why not using IRQF_SHARED?
> >
> > Probably because that particular IRQ is only used by the I2C
> > Controller.  I'm not exactly sure that you're getting at?  Why do you
> > think it should be shared?  You should only flag it as shared if it
> > is.
> 
> However, that's something the driver can't know.
> Sharing interrupts is an integration property. The same IP core may share its
> interrupt on one SoC, and not on another.

I guess that would depend on the IP.  If this is part of an MFD, you'd
know if you only hand a single interrupt line coming into the chip or
not.  If the IP can be moved around (copy & pasted) into different
chips, then yes, that might change.

How does one share an interrupt with other drivers if all them don't
know the IRQ is shared thought?

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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