Messages in this thread | | | Date | Mon, 16 Apr 2007 12:03:11 +0200 | From | "Francis Moreau" <> | Subject | Re: question on generic gpio interface |
| |
Hi David,
Thanks for your detailed answer, it helps a lot !
On 4/14/07, David Brownell <david-b@pacbell.net> wrote: > On Friday 13 April 2007 1:51 pm, Francis Moreau wrote: > > Hi, > > > > I'm trying to port my old gpio code to the generic one to see if it > > can fit my needs. > > Good .. this is more like an IRQ question though. >
yeah now it appears to me so...
> > > The gpio controller is a home made one and has a really weird > > interface. It has several registers to read the gpio status, to > > configure gpio directions, or to configure if a gpio can trigger an > > interrupt and on which event (level or edge). All gpios use the same > > IRQ and a gpio controller register allows to read which gpio has > > triggered the interrupt. > > I'll trust you on "weird", but that sounds quite typical in > terms of functionality. You'll find that most system-on-chip > GPIO controllers act the same way. > > IRQ logic on that platform must do a few things, like: > > - NR_IRQS includes the N interrupts triggered from that chip, > and their numbers probably fit right sometimes after the > core set of IRQs (which might include SOC GPIO irqs); > > - You'll provide an irq_chip for this controller, and it will > handle the relevant irq operations (set trigger type, mask, > unmask etc); > > - When configuring the IRQ handler for that "same IRQ", you'll > set it up to use a chained handler that you provide, which > reads the register to see which gpio(s) triggered the IRQ, > maybe acks it (if just reading that register isn't enough), > and then calls whatever handler was instaled for that GPIO. > > If that's not familiar to you, look at arch/arm/mach-at91/gpio.c > or arch/arm/mach-pxa/irq.c or arch/arm/plat-omap/gpio.c or a > number of other similar files showing how the "toplevel" IRQ > logic will demux from a "one of these N GPIOs" interrupt down > to the handler for that particular IRQ. >
I think I got the picture now, thanks again.
Just to be sure I understand, it seems to me that your point 2) and 3) are 2 different approaches to do the same thing, aren't they ?
If so I can only implement 2) since it seems to me better than the last one (it better uses genirq layer).
Thanks ! -- Francis - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |