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author | Thomas Petazzoni <thomas.petazzoni@bootlin.com> | 2019-02-07 17:28:55 +0100 |
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committer | Linus Walleij <linus.walleij@linaro.org> | 2019-02-13 09:07:43 +0100 |
commit | ede033e1e863c36729de25b57145fff287415830 (patch) | |
tree | 51113627e623b97fcb8f647dd06431b316cc5ceb /drivers/gpio/gpiolib.c | |
parent | bfeffd155283772bbe78c6a05dec7c0128ee500c (diff) |
dt-bindings: gpio: document the new pull-up/pull-down flags
This commit extends the flags that can be used in GPIO specifiers to
indicate if a pull-up resistor or pull-down resistor should be
enabled.
While some pinctrl DT bindings already offer the capability of
configuring pull-up/pull-down resistors at the pin level, a number of
simple GPIO controllers don't have any pinmuxing capability, and
therefore do not rely on the pinctrl DT bindings.
Such simple GPIO controllers however sometimes allow to configure
pull-up and pull-down resistors on a per-pin basis, and whether such
resistors should be enabled or not is a highly board-specific HW
characteristic.
By using two additional bits of the GPIO flag specifier, we can easily
allow the Device Tree to describe which GPIOs should have their
pull-up or pull-down resistors enabled. Even though the two options
are mutually exclusive, we still need two bits to encode at least
three states: no pull-up/pull-down, pull-up, pull-down.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Diffstat (limited to 'drivers/gpio/gpiolib.c')
0 files changed, 0 insertions, 0 deletions