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:
> > 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 <john.stultz@xxxxxxxxxx>
> > Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxxxxxx>
> > ---
> > 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
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