pon., 8 lip 2019 o 07:23 Michael Wu <michael.wu@xxxxxxxxxx> napisał(a): > > When a pin is active-low, logical trigger edge should be inverted to match > the same interrupt opportunity. > > For example, a button pushed triggers falling edge in ACTIVE_HIGH case; in > ACTIVE_LOW case, the button pushed triggers rising edge. For user space the > IRQ requesting doesn't need to do any modification except to configuring > GPIOHANDLE_REQUEST_ACTIVE_LOW. > > For example, we want to catch the event when the button is pushed. The > button on the original board drives level to be low when it is pushed, and > drives level to be high when it is released. > > In user space we can do: > > req.handleflags = GPIOHANDLE_REQUEST_INPUT; > req.eventflags = GPIOEVENT_REQUEST_FALLING_EDGE; > > while (1) { > read(fd, &dat, sizeof(dat)); > if (dat.id == GPIOEVENT_EVENT_FALLING_EDGE) > printf("button pushed\n"); > } > > Run the same logic on another board which the polarity of the button is > inverted; it drives level to be high when pushed, and level to be low when > released. For this inversion we add flag GPIOHANDLE_REQUEST_ACTIVE_LOW: > > req.handleflags = GPIOHANDLE_REQUEST_INPUT | > GPIOHANDLE_REQUEST_ACTIVE_LOW; > req.eventflags = GPIOEVENT_REQUEST_FALLING_EDGE; > > At the result, there are no any events caught when the button is pushed. > By the way, button releasing will emit a "falling" event. The timing of > "falling" catching is not expected. > > Cc: stable@xxxxxxxxxxxxxxx > Signed-off-by: Michael Wu <michael.wu@xxxxxxxxxx> > --- > Changes from v1: > - Correct undeclared 'IRQ_TRIGGER_RISING' > - Add an example to descibe the issue > --- > drivers/gpio/gpiolib.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c > index e013d417a936..9c9597f929d7 100644 > --- a/drivers/gpio/gpiolib.c > +++ b/drivers/gpio/gpiolib.c > @@ -956,9 +956,11 @@ static int lineevent_create(struct gpio_device *gdev, void __user *ip) > } > > if (eflags & GPIOEVENT_REQUEST_RISING_EDGE) > - irqflags |= IRQF_TRIGGER_RISING; > + irqflags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ? > + IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING; > if (eflags & GPIOEVENT_REQUEST_FALLING_EDGE) > - irqflags |= IRQF_TRIGGER_FALLING; > + irqflags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ? > + IRQF_TRIGGER_RISING : IRQF_TRIGGER_FALLING; > irqflags |= IRQF_ONESHOT; > > INIT_KFIFO(le->events); > -- > 2.17.1 > Tested-by: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx> Reviewed-by: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>