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| author | Linus Walleij <linus.walleij@linaro.org> | 2018-09-25 09:54:14 +0200 |
|---|---|---|
| committer | Linus Walleij <linus.walleij@linaro.org> | 2018-09-25 09:54:14 +0200 |
| commit | e48d194d1204b19655c1a9d78a67f2f01d2fe432 (patch) | |
| tree | 13655545f5f1c22547a171b23c56eb98ded6a09b /include | |
| parent | gpiolib: Fix gpio_direction_* for single direction GPIOs (diff) | |
| download | linux-e48d194d1204b19655c1a9d78a67f2f01d2fe432.tar.xz linux-e48d194d1204b19655c1a9d78a67f2f01d2fe432.zip | |
gpio: Add comments on single direction chips
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>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/gpio/driver.h | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h index d8dcd0e44cab..f6b95734073f 100644 --- a/include/linux/gpio/driver.h +++ b/include/linux/gpio/driver.h @@ -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 |