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authorDmitry Torokhov <dmitry.torokhov@gmail.com>2017-02-12 17:13:55 -0800
committerLinus Walleij <linus.walleij@linaro.org>2017-03-15 11:16:30 +0100
commit22c403676dbbb7c6f186099527af7f065498ef45 (patch)
treeb4c165eee3ec51b83a17bd1d62f5e0851d28287c /Documentation/gpio
parent85c73d50e57eb8ad43955fe38714bc5fba1acd92 (diff)
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gpio: return NULL from gpiod_get_optional when GPIOLIB is disabled
Given the intent behind gpiod_get_optional() and friends it does not make sense to return -ENOSYS when GPIOLIB is disabled: the driver is expected to work just fine without gpio so let's behave as if gpio was not found. Otherwise we have to special-case -ENOSYS in drivers. Note that there was objection that someone might forget to enable GPIOLIB when dealing with a platform that has device that actually specifies optional gpio and we'll break it. I find this unconvincing as that would have to be the *only GPIO* in the system, which is extremely unlikely. Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Diffstat (limited to 'Documentation/gpio')
-rw-r--r--Documentation/gpio/consumer.txt6
1 files changed, 6 insertions, 0 deletions
diff --git a/Documentation/gpio/consumer.txt b/Documentation/gpio/consumer.txt
index 05676fdacfe3..912568baabb9 100644
--- a/Documentation/gpio/consumer.txt
+++ b/Documentation/gpio/consumer.txt
@@ -70,6 +70,12 @@ instead of -ENOENT if no GPIO has been assigned to the requested function:
unsigned int index,
enum gpiod_flags flags)
+Note that gpio_get*_optional() functions (and their managed variants), unlike
+the rest of gpiolib API, also return NULL when gpiolib support is disabled.
+This is helpful to driver authors, since they do not need to special case
+-ENOSYS return codes. System integrators should however be careful to enable
+gpiolib on systems that need it.
+
For a function using multiple GPIOs all of those can be obtained with one call:
struct gpio_descs *gpiod_get_array(struct device *dev,