gpio: <linux/gpio.h> and "no GPIO support here" stubs (7560fa60) · Commits · 戴 / test

Documentation/gpio.txt

+12 −4

Original line number	Diff line number	Diff line
		@@ -2,6 +2,9 @@ GPIO Interfaces

		This provides an overview of GPIO access conventions on Linux.

		These calls use the gpio_* naming prefix. No other calls should use that
		prefix, or the related __gpio_* prefix.


		What is a GPIO?
		===============
		@@ -69,11 +72,13 @@ in this document, but drivers acting as clients to the GPIO interface must
		not care how it's implemented.)

		That said, if the convention is supported on their platform, drivers should
		use it when possible. Platforms should declare GENERIC_GPIO support in
		Kconfig (boolean true), which multi-platform drivers can depend on when
		using the include file:
		use it when possible. Platforms must declare GENERIC_GPIO support in their
		Kconfig (boolean true), and provide an <asm/gpio.h> file. Drivers that can't
		work without standard GPIO calls should have Kconfig entries which depend
		on GENERIC_GPIO. The GPIO calls are available, either as "real code" or as
		optimized-away stubs, when drivers use the include file:

		#include <asm/gpio.h>
		#include <linux/gpio.h>

		If you stick to this convention then it'll be easier for other developers to
		see what your code is doing, and help maintain it.
		@@ -316,6 +321,9 @@ pulldowns integrated on some platforms. Not all platforms support them,
		or support them in the same way; and any given board might use external
		pullups (or pulldowns) so that the on-chip ones should not be used.
		(When a circuit needs 5 kOhm, on-chip 100 kOhm resistors won't do.)
		Likewise drive strength (2 mA vs 20 mA) and voltage (1.8V vs 3.3V) is a
		platform-specific issue, as are models like (not) having a one-to-one
		correspondence between configurable pins and GPIOs.

		There are other system-specific mechanisms that are not specified here,
		like the aforementioned options for input de-glitching and wire-OR output.

include/linux/gpio.h

0 → 100644

+95 −0

Original line number	Diff line number	Diff line
		#ifndef __LINUX_GPIO_H
		#define __LINUX_GPIO_H

		/* see Documentation/gpio.txt */

		#ifdef CONFIG_GENERIC_GPIO
		#include <asm/gpio.h>

		#else

		/*
		* Some platforms don't support the GPIO programming interface.
		*
		* In case some driver uses it anyway (it should normally have
		* depended on GENERIC_GPIO), these routines help the compiler
		* optimize out much GPIO-related code ... or trigger a runtime
		* warning when something is wrongly called.
		*/

		static inline int gpio_is_valid(int number)
		{
		return 0;
		}

		static inline int gpio_request(unsigned gpio, const char *label)
		{
		return -ENOSYS;
		}

		static inline void gpio_free(unsigned gpio)
		{
		/* GPIO can never have been requested */
		WARN_ON(1);
		}

		static inline int gpio_direction_input(unsigned gpio)
		{
		return -ENOSYS;
		}

		static inline int gpio_direction_output(unsigned gpio, int value)
		{
		return -ENOSYS;
		}

		static inline int gpio_get_value(unsigned gpio)
		{
		/* GPIO can never have been requested or set as {in,out}put */
		WARN_ON(1);
		return 0;
		}

		static inline void gpio_set_value(unsigned gpio, int value)
		{
		/* GPIO can never have been requested or set as output */
		WARN_ON(1);
		}

		static inline int gpio_cansleep(unsigned gpio)
		{
		/* GPIO can never have been requested or set as {in,out}put */
		WARN_ON(1);
		return 0;
		}

		static inline int gpio_get_value_cansleep(unsigned gpio)
		{
		/* GPIO can never have been requested or set as {in,out}put */
		WARN_ON(1);
		return 0;
		}

		static inline void gpio_set_value_cansleep(unsigned gpio, int value)
		{
		/* GPIO can never have been requested or set as output */
		WARN_ON(1);
		}

		static inline int gpio_to_irq(unsigned gpio)
		{
		/* GPIO can never have been requested or set as input */
		WARN_ON(1);
		return -EINVAL;
		}

		static inline int irq_to_gpio(unsigned irq)
		{
		/* irq can never have been returned from gpio_to_irq() */
		WARN_ON(1);
		return -EINVAL;
		}

		#endif

		#endif /* __LINUX_GPIO_H */

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