diff options
| -rw-r--r-- | drivers/gpio/gpiolib.c | 33 | ||||
| -rw-r--r-- | include/linux/gpio/driver.h | 6 |
2 files changed, 32 insertions, 7 deletions
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index cabe1b460458..4ce402f9fc69 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -2548,20 +2548,31 @@ int gpiod_direction_input(struct gpio_desc *desc) VALIDATE_DESC(desc); chip = desc->gdev->chip; + /* + * It is legal to have no .get() and .direction_input() specified if + * the chip is output-only, but you can't specify .direction_input() + * and not support the .get() operation, that doesn't make sense. + */ if (!chip->get && chip->direction_input) { gpiod_warn(desc, - "%s: missing get() and direction_input() operations\n", - __func__); + "%s: missing get() but have direction_input()\n", + __func__); return -EIO; } + /* + * If we have a .direction_input() callback, things are simple, + * just call it. Else we are some input-only chip so try to check the + * direction (if .get_direction() is supported) else we silently + * assume we are in input mode after this. + */ if (chip->direction_input) { status = chip->direction_input(chip, gpio_chip_hwgpio(desc)); } else if (chip->get_direction && (chip->get_direction(chip, gpio_chip_hwgpio(desc)) != 1)) { gpiod_warn(desc, - "%s: missing direction_input() operation\n", - __func__); + "%s: missing direction_input() operation and line is output\n", + __func__); return -EIO; } if (status == 0) @@ -2587,16 +2598,22 @@ static int gpiod_direction_output_raw_commit(struct gpio_desc *desc, int value) int val = !!value; int ret = 0; + /* + * It's OK not to specify .direction_output() if the gpiochip is + * output-only, but if there is then not even a .set() operation it + * is pretty tricky to drive the output line. + */ if (!gc->set && !gc->direction_output) { gpiod_warn(desc, - "%s: missing set() and direction_output() operations\n", - __func__); + "%s: missing set() and direction_output() operations\n", + __func__); return -EIO; } if (gc->direction_output) { ret = gc->direction_output(gc, gpio_chip_hwgpio(desc), val); } else { + /* Check that we are in output mode if we can */ if (gc->get_direction && gc->get_direction(gc, gpio_chip_hwgpio(desc))) { gpiod_warn(desc, @@ -2604,6 +2621,10 @@ static int gpiod_direction_output_raw_commit(struct gpio_desc *desc, int value) __func__); return -EIO; } + /* + * If we can't actively set the direction, we are some + * output-only chip, so just drive the output as desired. + */ gc->set(gc, gpio_chip_hwgpio(desc), val); } 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 |