gpio: Add comments on single direction chips (e48d194d) · Commits · 戴 / test

drivers/gpio/gpiolib.c

+27 −6

Original line number	Diff line number	Diff line
		@@ -2548,19 +2548,30 @@ 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",
		"%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",
		"%s: missing direction_input() operation and line is output\n",
		__func__);
		return -EIO;
		}
		@@ -2587,6 +2598,11 @@ 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",
		@@ -2597,6 +2613,7 @@ static int gpiod_direction_output_raw_commit(struct gpio_desc *desc, int value)
		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);
		}

include/linux/gpio/driver.h

+5 −1

Original line number	Diff line number	Diff line
		@@ -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

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