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

From: Lee Jones
Date: Fri May 08 2015 - 02:57:57 EST

On Fri, 08 May 2015, Geert Uytterhoeven wrote:

> On Thu, May 7, 2015 at 9:01 AM, Lee Jones <lee.jones@xxxxxxxxxx> 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 â Open source software for ARM SoCs
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