d8f388d8dc
This adds a simple sysfs interface for GPIOs.
/sys/class/gpio
/export ... asks the kernel to export a GPIO to userspace
/unexport ... to return a GPIO to the kernel
/gpioN ... for each exported GPIO #N
/value ... always readable, writes fail for input GPIOs
/direction ... r/w as: in, out (default low); write high, low
/gpiochipN ... for each gpiochip; #N is its first GPIO
/base ... (r/o) same as N
/label ... (r/o) descriptive, not necessarily unique
/ngpio ... (r/o) number of GPIOs; numbered N .. N+(ngpio - 1)
GPIOs claimed by kernel code may be exported by its owner using a new
gpio_export() call, which should be most useful for driver debugging.
Such exports may optionally be done without a "direction" attribute.
Userspace may ask to take over a GPIO by writing to a sysfs control file,
helping to cope with incomplete board support or other "one-off"
requirements that don't merit full kernel support:
echo 23 > /sys/class/gpio/export
... will gpio_request(23, "sysfs") and gpio_export(23);
use /sys/class/gpio/gpio-23/direction to (re)configure it,
when that GPIO can be used as both input and output.
echo 23 > /sys/class/gpio/unexport
... will gpio_free(23), when it was exported as above
The extra D-space footprint is a few hundred bytes, except for the sysfs
resources associated with each exported GPIO. The additional I-space
footprint is about two thirds of the current size of gpiolib (!). Since
no /dev node creation is involved, no "udev" support is needed.
Related changes:
* This adds a device pointer to "struct gpio_chip". When GPIO
providers initialize that, sysfs gpio class devices become children of
that device instead of being "virtual" devices.
* The (few) gpio_chip providers which have such a device node have
been updated.
* Some gpio_chip drivers also needed to update their module "owner"
field ... for which missing kerneldoc was added.
* Some gpio_chips don't support input GPIOs. Those GPIOs are now
flagged appropriately when the chip is registered.
Based on previous patches, and discussion both on and off LKML.
A Documentation/ABI/testing/sysfs-gpio update is ready to submit once this
merges to mainline.
[akpm@linux-foundation.org: a few maintenance build fixes]
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Guennadi Liakhovetski <g.liakhovetski@pengutronix.de>
Cc: Greg KH <greg@kroah.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
172 lines
5.1 KiB
C
172 lines
5.1 KiB
C
#ifndef _ASM_GENERIC_GPIO_H
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#define _ASM_GENERIC_GPIO_H
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#include <linux/types.h>
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#ifdef CONFIG_HAVE_GPIO_LIB
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#include <linux/compiler.h>
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/* Platforms may implement their GPIO interface with library code,
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* at a small performance cost for non-inlined operations and some
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* extra memory (for code and for per-GPIO table entries).
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*
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* While the GPIO programming interface defines valid GPIO numbers
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* to be in the range 0..MAX_INT, this library restricts them to the
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* smaller range 0..ARCH_NR_GPIOS.
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*/
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#ifndef ARCH_NR_GPIOS
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#define ARCH_NR_GPIOS 256
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#endif
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static inline int gpio_is_valid(int number)
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{
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/* only some non-negative numbers are valid */
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return ((unsigned)number) < ARCH_NR_GPIOS;
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}
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struct seq_file;
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struct module;
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/**
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* struct gpio_chip - abstract a GPIO controller
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* @label: for diagnostics
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* @dev: optional device providing the GPIOs
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* @owner: helps prevent removal of modules exporting active GPIOs
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* @direction_input: configures signal "offset" as input, or returns error
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* @get: returns value for signal "offset"; for output signals this
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* returns either the value actually sensed, or zero
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* @direction_output: configures signal "offset" as output, or returns error
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* @set: assigns output value for signal "offset"
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* @dbg_show: optional routine to show contents in debugfs; default code
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* will be used when this is omitted, but custom code can show extra
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* state (such as pullup/pulldown configuration).
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* @base: identifies the first GPIO number handled by this chip; or, if
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* negative during registration, requests dynamic ID allocation.
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* @ngpio: the number of GPIOs handled by this controller; the last GPIO
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* handled is (base + ngpio - 1).
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* @can_sleep: flag must be set iff get()/set() methods sleep, as they
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* must while accessing GPIO expander chips over I2C or SPI
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*
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* A gpio_chip can help platforms abstract various sources of GPIOs so
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* they can all be accessed through a common programing interface.
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* Example sources would be SOC controllers, FPGAs, multifunction
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* chips, dedicated GPIO expanders, and so on.
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*
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* Each chip controls a number of signals, identified in method calls
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* by "offset" values in the range 0..(@ngpio - 1). When those signals
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* are referenced through calls like gpio_get_value(gpio), the offset
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* is calculated by subtracting @base from the gpio number.
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*/
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struct gpio_chip {
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char *label;
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struct device *dev;
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struct module *owner;
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int (*direction_input)(struct gpio_chip *chip,
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unsigned offset);
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int (*get)(struct gpio_chip *chip,
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unsigned offset);
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int (*direction_output)(struct gpio_chip *chip,
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unsigned offset, int value);
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void (*set)(struct gpio_chip *chip,
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unsigned offset, int value);
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void (*dbg_show)(struct seq_file *s,
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struct gpio_chip *chip);
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int base;
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u16 ngpio;
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unsigned can_sleep:1;
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unsigned exported:1;
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};
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extern const char *gpiochip_is_requested(struct gpio_chip *chip,
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unsigned offset);
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extern int __must_check gpiochip_reserve(int start, int ngpio);
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/* add/remove chips */
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extern int gpiochip_add(struct gpio_chip *chip);
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extern int __must_check gpiochip_remove(struct gpio_chip *chip);
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/* Always use the library code for GPIO management calls,
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* or when sleeping may be involved.
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*/
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extern int gpio_request(unsigned gpio, const char *label);
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extern void gpio_free(unsigned gpio);
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extern int gpio_direction_input(unsigned gpio);
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extern int gpio_direction_output(unsigned gpio, int value);
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extern int gpio_get_value_cansleep(unsigned gpio);
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extern void gpio_set_value_cansleep(unsigned gpio, int value);
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/* A platform's <asm/gpio.h> code may want to inline the I/O calls when
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* the GPIO is constant and refers to some always-present controller,
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* giving direct access to chip registers and tight bitbanging loops.
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*/
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extern int __gpio_get_value(unsigned gpio);
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extern void __gpio_set_value(unsigned gpio, int value);
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extern int __gpio_cansleep(unsigned gpio);
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#ifdef CONFIG_GPIO_SYSFS
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/*
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* A sysfs interface can be exported by individual drivers if they want,
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* but more typically is configured entirely from userspace.
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*/
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extern int gpio_export(unsigned gpio, bool direction_may_change);
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extern void gpio_unexport(unsigned gpio);
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#endif /* CONFIG_GPIO_SYSFS */
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#else /* !CONFIG_HAVE_GPIO_LIB */
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static inline int gpio_is_valid(int number)
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{
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/* only non-negative numbers are valid */
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return number >= 0;
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}
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/* platforms that don't directly support access to GPIOs through I2C, SPI,
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* or other blocking infrastructure can use these wrappers.
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*/
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static inline int gpio_cansleep(unsigned gpio)
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{
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return 0;
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}
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static inline int gpio_get_value_cansleep(unsigned gpio)
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{
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might_sleep();
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return gpio_get_value(gpio);
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}
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static inline void gpio_set_value_cansleep(unsigned gpio, int value)
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{
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might_sleep();
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gpio_set_value(gpio, value);
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}
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#endif /* !CONFIG_HAVE_GPIO_LIB */
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#ifndef CONFIG_GPIO_SYSFS
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/* sysfs support is only available with gpiolib, where it's optional */
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static inline int gpio_export(unsigned gpio, bool direction_may_change)
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{
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return -ENOSYS;
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}
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static inline void gpio_unexport(unsigned gpio)
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{
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}
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#endif /* CONFIG_GPIO_SYSFS */
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#endif /* _ASM_GENERIC_GPIO_H */
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