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gpio: Add comments on single direction chips

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A patch from Ricardo got me thinking about some gpio chip
semantics so let's drop in some comments to make things
more clear around that.

Cc: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
This commit is contained in:
Linus Walleij
2018-09-25 09:54:14 +02:00
parent ae9847f48a
commit e48d194d12
2 changed files with 32 additions and 7 deletions
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6
include/linux/gpio/driver.h
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@@ -178,9 +178,13 @@ static inline struct gpio_irq_chip *to_gpio_irq_chip(struct irq_chip *chip)
* @free: optional hook for chip-specific deactivation, such as
* disabling module power and clock; may sleep
* @get_direction: returns direction for signal "offset", 0=out, 1=in,
* (same as GPIOF_DIR_XXX), or negative error
* (same as GPIOF_DIR_XXX), or negative error.
* It is recommended to always implement this function, even on
* input-only or output-only gpio chips.
* @direction_input: configures signal "offset" as input, or returns error
* This can be omitted on input-only or output-only gpio chips.
* @direction_output: configures signal "offset" as output, or returns error
* This can be omitted on input-only or output-only gpio chips.
* @get: returns value for signal "offset", 0=low, 1=high, or negative error
* @get_multiple: reads values for multiple signals defined by "mask" and
* stores them in "bits", returns 0 on success or negative error