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Date: Thu, 11 Jun 2015 08:29:10 +0800 From: Amos Jianjun Kong <kongjianjun@...il.com> To: Mika Westerberg <mika.westerberg@...ux.intel.com> Cc: Linus Walleij <linus.walleij@...aro.org>, Alexandre Courbot <gnurou@...il.com>, "Rafael J. Wysocki" <rjw@...ysocki.net>, Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Tobias Diedrich <tobiasdiedrich@...il.com>, linux-gpio@...r.kernel.org, open list <linux-kernel@...r.kernel.org> Subject: Re: [PATCH] gpio / ACPI: Return -EPROBE_DEFER if the gpiochip was not found On Wed, Jun 10, 2015 at 9:05 PM, Mika Westerberg <mika.westerberg@...ux.intel.com> wrote: > If a driver requests a GPIO described in its _CRS but the GPIO host > controller (gpiochip) driver providing the GPIO has not been loaded yet > acpi_get_gpiod() returns -ENODEV which causes the calling driver to fail. > > If the gpiochip driver is loaded afterwards the driver requesting the GPIO > will not notice this. > > Better approach is to return -EPROBE_DEFER in such case. Then when the > gpiochip driver appears the driver requesting the GPIO will be probed > again. This also aligns ACPI GPIO lookup code closer to DT as it does > pretty much the same when no gpiochip driver was found. > > Reported-by: Tobias Diedrich <tobiasdiedrich@...il.com> > Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com> > --- > drivers/gpio/gpiolib-acpi.c | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpio/gpiolib-acpi.c b/drivers/gpio/gpiolib-acpi.c > index 19b99d0c2bf0..b49006c81a7f 100644 > --- a/drivers/gpio/gpiolib-acpi.c > +++ b/drivers/gpio/gpiolib-acpi.c > @@ -114,10 +114,11 @@ static inline int acpi_gpiochip_pin_to_gpio_offset(struct gpio_chip *chip, > * @path: ACPI GPIO controller full path name, (e.g. "\\_SB.GPO1") > * @pin: ACPI GPIO pin number (0-based, controller-relative) > * > - * Returns GPIO descriptor to use with Linux generic GPIO API, or ERR_PTR > - * error value > + * Return: GPIO descriptor to use with Linux generic GPIO API, or ERR_PTR > + * error value. Specifically returns %-EPROBE_DEFER if the referenced GPIO > + * controller does not have gpiochip registered at the moment. This is to > + * support probe deferral. > */ > - api_get_gpiod() is called in preprobe stage, we still have chance to probe the device. Reviewed-by: Amos Kong <kongjianjun@...il.com> > static struct gpio_desc *acpi_get_gpiod(char *path, int pin) > { > struct gpio_chip *chip; > @@ -131,7 +132,7 @@ static struct gpio_desc *acpi_get_gpiod(char *path, int pin) > > chip = gpiochip_find(handle, acpi_gpiochip_find); > if (!chip) > - return ERR_PTR(-ENODEV); > + return ERR_PTR(-EPROBE_DEFER); > > offset = acpi_gpiochip_pin_to_gpio_offset(chip, pin); > if (offset < 0) > -- > 2.1.4 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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