On Fri, 08 May 2015, Geert Uytterhoeven wrote: > On Fri, May 8, 2015 at 8:57 AM, Lee Jones <lee.jones@xxxxxxxxxx> wrote: > > 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? > > 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. Precisely, which is why I'm confused by: "However, that's something the driver can't know." -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
