On Tue 28 Jul 14:00 PDT 2015, Dmitry Torokhov wrote:

Hi Bjorn,

On Mon, Jul 27, 2015 at 06:50:04PM -0700, Bjorn Andersson wrote:

quoted

In the cases where the gpio chip fails to acquire the current state an
error is reported back to gpio_keys. This is currently interpreted as if
the line went high, which just confuses the developer.

This patch introduces an error print in this case and skipps the
reporting of a input event; to aid in debugging this issue.

Reported-by: John Stultz <redacted>
Signed-off-by: Bjorn Andersson <redacted>
---
 drivers/input/keyboard/gpio_keys.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/input/keyboard/gpio_keys.c b/drivers/input/keyboard/gpio_keys.c
index ddf4045de084..3ce3298ac09e 100644
--- a/drivers/input/keyboard/gpio_keys.c
+++ b/drivers/input/keyboard/gpio_keys.c

@@ -336,8 +336,14 @@ static void gpio_keys_gpio_report_event(struct gpio_button_data *bdata)
 	const struct gpio_keys_button *button = bdata->button;
 	struct input_dev *input = bdata->input;
 	unsigned int type = button->type ?: EV_KEY;
-	int state = (gpio_get_value_cansleep(button->gpio) ? 1 : 0) ^ button->active_low;
+	int state = gpio_get_value_cansleep(button->gpio);
 
+	if (state < 0) {
+		dev_err(input->dev.parent, "failed to get gpio state\n");

As far as I can see:

static inline int gpio_get_value_cansleep(unsigned gpio)
{
	return gpiod_get_raw_value_cansleep(gpio_to_desc(gpio));
}

int gpiod_get_raw_value_cansleep(const struct gpio_desc *desc)
{
	might_sleep_if(extra_checks);
	if (!desc)
		return 0;
	return _gpiod_get_raw_value(desc);
}

static bool _gpiod_get_raw_value(const struct gpio_desc *desc)
{
...
}

So how exactly do we get negative here?

I'm sorry, I obviously didn't pay enough attention when running through
that callstack...

But then the question first goes to Linus & co.

gpio_chip->get() can return a negative value to indicate errors (and did
so in this case), all parts of the API seems indicates that we can get
an error (int vs bool).

Should we change _gpiod_get_raw_value() to propagate this error?  Or
should we just ignore this issue and propagate an error as GPIO high
reading?

Regards,
Bjorn