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438d8908b3
As long as one or more GPIOs on a gpio chip are used its driver should not be unloaded. The existing mechanism (gpiochip_remove failure) doesn't address that, since rmmod can no longer be made to fail by having the cleanup code report errors. Module usecounts are the solution. Assuming standard "initialize struct to zero" policies, this change won't affect SOC platform drivers. However, drivers for external chips (on I2C and SPI busses) should be updated if they can be built as modules. Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@pengutronix.de> [ gpio_ensure_requested() needs to update module usecounts too ] Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
126 lines
3.9 KiB
C
126 lines
3.9 KiB
C
#ifndef _ASM_GENERIC_GPIO_H
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#define _ASM_GENERIC_GPIO_H
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#ifdef CONFIG_HAVE_GPIO_LIB
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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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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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* @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 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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};
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extern const char *gpiochip_is_requested(struct gpio_chip *chip,
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unsigned offset);
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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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#else
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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
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#endif /* _ASM_GENERIC_GPIO_H */
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