On Fri, May 8, 2015 at 8:57 AM, Lee Jones <lee.jo...@linaro.org> wrote: > On Fri, 08 May 2015, Geert Uytterhoeven wrote: > >> On Thu, May 7, 2015 at 9:01 AM, Lee Jones <lee.jo...@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?
All drivers sharing the same interrupt must pass IRQF_SHARED, cfr. the checks in __setup_irq(). Traditionally, PC (ISA) drivers didn't share interrupts, as the ISA bus prohibited interrupt sharing. Amiga drivers did. New drivers should support IRQ sharing. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/