On Wed, Dec 9, 2020 at 12:19 PM Arnd Bergmann <arnd@xxxxxxxxxx> wrote: > On Wed, Dec 9, 2020 at 9:51 AM Linus Walleij <linus.walleij@xxxxxxxxxx> wrote: > > On Tue, Dec 8, 2020 at 3:07 PM Enrico Weigelt, metux IT consult <lkml@xxxxxxxxx> wrote: > > > What we need to understand is if your new usecase is an outlier > > so it is simplest modeled by a "mock" irq_chip or we have to design > > something new altogether like notifications on changes. I suspect > > irq_chip would be best because all drivers using GPIOs for interrupts > > are expecting interrupts, and it would be an enormous task to > > change them all and really annoying to create a new mechanism > > on the side. > > I would expect the platform abstraction to actually be close enough > to a chained irqchip that it actually works: the notification should > come in via vring_interrupt(), which is a normal interrupt handler > that calls vq->vq.callback(), calling generic_handle_irq() (and > possibly chained_irq_enter()/chained_irq_exit() around it) like the > other gpio drivers do should just work here I think, and if it did > not, then I would expect this to be just a bug in the driver rather > than something missing in the gpio framework. Performance/latency-wise that would also be strongly encouraged. Tglx isn't super-happy about the chained interrupts at times, as they can create really nasty bugs, but a pure IRQ in fastpath of some kinde is preferable and intuitive either way. Yours, Linus Walleij
