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[PATCH] gpiolib: skip unwanted events, don't convert them to opposite edge

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  [PATCH] gpiolib: skip unwanted events, don't convert them to opposite edge Bartosz Golaszewski <brgl@bgdev.pl> - 2017-07-03 11:20 +0200
    Re: [PATCH] gpiolib: skip unwanted events, don't convert them to  opposite edge Andy Shevchenko <andy.shevchenko@gmail.com> - 2017-07-03 13:10 +0200
      Re: [PATCH] gpiolib: skip unwanted events, don't convert them to  opposite edge Bartosz Golaszewski <brgl@bgdev.pl> - 2017-07-04 16:30 +0200

#1679814 — [PATCH] gpiolib: skip unwanted events, don't convert them to opposite edge

The previous fix for filtering out of unwatched events was not entirely
correct. Instead of skipping the events we don't want, they are now
interpreted as events with opposing edge.

In order to fix it: always read the GPIO line value on interrupt and
only emit the event if it corresponds with the event type we requested.

Fixes: ad537b822577 ("gpiolib: fix filtering out unwanted events")
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
---
Hi Linus,

I tested my previous fix on a real board, where I got a storm of
interrupts from simply playing with a GPIO manually. It looked ok so I
posted the patch, but I didn't notice that when waiting for rising-edge
events, all falling-edge events got interpreted as such. This patch
should actually fix this bug. Tested carefully with gpio-mockup this
time.

 drivers/gpio/gpiolib.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index a42a1ee..2e96b3d 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -704,24 +704,23 @@ static irqreturn_t lineevent_irq_thread(int irq, void *p)
 {
 	struct lineevent_state *le = p;
 	struct gpioevent_data ge;
-	int ret;
+	int ret, level;
 
 	ge.timestamp = ktime_get_real_ns();
+	level = gpiod_get_value_cansleep(le->desc);
 
 	if (le->eflags & GPIOEVENT_REQUEST_RISING_EDGE
 	    && le->eflags & GPIOEVENT_REQUEST_FALLING_EDGE) {
-		int level = gpiod_get_value_cansleep(le->desc);
-
 		if (level)
 			/* Emit low-to-high event */
 			ge.id = GPIOEVENT_EVENT_RISING_EDGE;
 		else
 			/* Emit high-to-low event */
 			ge.id = GPIOEVENT_EVENT_FALLING_EDGE;
-	} else if (le->eflags & GPIOEVENT_REQUEST_RISING_EDGE) {
+	} else if (le->eflags & GPIOEVENT_REQUEST_RISING_EDGE && level) {
 		/* Emit low-to-high event */
 		ge.id = GPIOEVENT_EVENT_RISING_EDGE;
-	} else if (le->eflags & GPIOEVENT_REQUEST_FALLING_EDGE) {
+	} else if (le->eflags & GPIOEVENT_REQUEST_FALLING_EDGE && !level) {
 		/* Emit high-to-low event */
 		ge.id = GPIOEVENT_EVENT_FALLING_EDGE;
 	} else {
-- 
2.9.3

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#1679892 — Re: [PATCH] gpiolib: skip unwanted events, don't convert them to opposite edge

On Mon, Jul 3, 2017 at 12:12 PM, Bartosz Golaszewski <brgl@bgdev.pl> wrote:
> The previous fix for filtering out of unwatched events was not entirely
> correct. Instead of skipping the events we don't want, they are now
> interpreted as events with opposing edge.
>
> In order to fix it: always read the GPIO line value on interrupt and
> only emit the event if it corresponds with the event type we requested.

>         struct lineevent_state *le = p;
>         struct gpioevent_data ge;
> -       int ret;
> +       int ret, level;

I prefer
int level;
int ret;

Though it's matter of taste (I don't remember which one Linus' preferable).

-- 
With Best Regards,
Andy Shevchenko

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#1681023 — Re: [PATCH] gpiolib: skip unwanted events, don't convert them to opposite edge

2017-07-03 13:07 GMT+02:00 Andy Shevchenko <andy.shevchenko@gmail.com>:
> On Mon, Jul 3, 2017 at 12:12 PM, Bartosz Golaszewski <brgl@bgdev.pl> wrote:
>> The previous fix for filtering out of unwatched events was not entirely
>> correct. Instead of skipping the events we don't want, they are now
>> interpreted as events with opposing edge.
>>
>> In order to fix it: always read the GPIO line value on interrupt and
>> only emit the event if it corresponds with the event type we requested.
>
>>         struct lineevent_state *le = p;
>>         struct gpioevent_data ge;
>> -       int ret;
>> +       int ret, level;
>
> I prefer
> int level;
> int ret;
>
> Though it's matter of taste (I don't remember which one Linus' preferable).
>
> --
> With Best Regards,
> Andy Shevchenko

Hard to tell, the file uses both styles.

Thanks,
Bartosz

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