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gpio: generic: add new generic GPIO chip API

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As the first step in removing the fields specific to the gpio-mmio
module from struct gpio_chip, we introduce a new set of generic GPIO
chip interfaces that are meant to replace the existing bgpio_ ones.

The new initialization function - gpio_generic_chip_init() - takes a
configuration structure as argument instead of 9 separate parameters.
This will allow easy extension if needed in the future. We hide the
locking details behind a set of helpers in order to be able to move the
raw spinlock out of struct gpio_chip without the users noticing.

For now, the new APIs just wrap the existing ones. Once all users have
been converted to the new interfaces, we'll pull them into gpio-mmio and
implement them in a backward-compatible way while also moving all fields
specific to the generic GPIO chip into struct gpio_generic_chip.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20250702-gpio-mmio-rework-v2-1-6b77aab684d8@linaro.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
This commit is contained in:
Bartosz Golaszewski 2025-07-02 11:22:08 +02:00
parent 179a666951
commit 8595375e4f
1 changed files with 120 additions and 0 deletions
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120
include/linux/gpio/generic.h Normal file
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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_GPIO_GENERIC_H
#define __LINUX_GPIO_GENERIC_H
#include <linux/cleanup.h>
#include <linux/gpio/driver.h>
#include <linux/spinlock.h>
struct device;
/**
* struct gpio_generic_chip_config - Generic GPIO chip configuration data
* @dev: Parent device of the new GPIO chip (compulsory).
* @sz: Size (width) of the MMIO registers in bytes, typically 1, 2 or 4.
* @dat: MMIO address for the register to READ the value of the GPIO lines, it
* is expected that a 1 in the corresponding bit in this register means
* the line is asserted.
* @set: MMIO address for the register to SET the value of the GPIO lines, it
* is expected that we write the line with 1 in this register to drive
* the GPIO line high.
* @clr: MMIO address for the register to CLEAR the value of the GPIO lines,
* it is expected that we write the line with 1 in this register to
* drive the GPIO line low. It is allowed to leave this address as NULL,
* in that case the SET register will be assumed to also clear the GPIO
* lines, by actively writing the line with 0.
* @dirout: MMIO address for the register to set the line as OUTPUT. It is
* assumed that setting a line to 1 in this register will turn that
* line into an output line. Conversely, setting the line to 0 will
* turn that line into an input.
* @dirin: MMIO address for the register to set this line as INPUT. It is
* assumed that setting a line to 1 in this register will turn that
* line into an input line. Conversely, setting the line to 0 will
* turn that line into an output.
* @flags: Different flags that will affect the behaviour of the device, such
* as endianness etc.
*/
struct gpio_generic_chip_config {
struct device *dev;
unsigned long sz;
void __iomem *dat;
void __iomem *set;
void __iomem *clr;
void __iomem *dirout;
void __iomem *dirin;
unsigned long flags;
};
/**
* struct gpio_generic_chip - Generic GPIO chip implementation.
* @gc: The underlying struct gpio_chip object, implementing low-level GPIO
* chip routines.
*/
struct gpio_generic_chip {
struct gpio_chip gc;
};
/**
* gpio_generic_chip_init() - Initialize a generic GPIO chip.
* @chip: Generic GPIO chip to set up.
* @cfg: Generic GPIO chip configuration.
*
* Returns 0 on success, negative error number on failure.
*/
static inline int
gpio_generic_chip_init(struct gpio_generic_chip *chip,
const struct gpio_generic_chip_config *cfg)
{
return bgpio_init(&chip->gc, cfg->dev, cfg->sz, cfg->dat, cfg->set,
cfg->clr, cfg->dirout, cfg->dirin, cfg->flags);
}
/**
* gpio_generic_chip_set() - Set the GPIO line value of the generic GPIO chip.
* @chip: Generic GPIO chip to use.
* @offset: Hardware offset of the line to set.
* @value: New GPIO line value.
*
* Some modules using the generic GPIO chip, need to set line values in their
* direction setters but they don't have access to the gpio-mmio symbols so
* they use the function pointer in struct gpio_chip directly. This is not
* optimal and can lead to crashes at run-time in some instances. This wrapper
* provides a safe interface for users.
*
* Returns: 0 on success, negative error number of failure.
*/
static inline int
gpio_generic_chip_set(struct gpio_generic_chip *chip, unsigned int offset,
int value)
{
if (WARN_ON(!chip->gc.set_rv))
return -EOPNOTSUPP;
return chip->gc.set_rv(&chip->gc, offset, value);
}
#define gpio_generic_chip_lock(gen_gc) \
raw_spin_lock(&(gen_gc)->gc.bgpio_lock)
#define gpio_generic_chip_unlock(gen_gc) \
raw_spin_unlock(&(gen_gc)->gc.bgpio_lock)
#define gpio_generic_chip_lock_irqsave(gen_gc, flags) \
raw_spin_lock_irqsave(&(gen_gc)->gc.bgpio_lock, flags)
#define gpio_generic_chip_unlock_irqrestore(gen_gc, flags) \
raw_spin_unlock_irqrestore(&(gen_gc)->gc.bgpio_lock, flags)
DEFINE_LOCK_GUARD_1(gpio_generic_lock,
struct gpio_generic_chip,
gpio_generic_chip_lock(_T->lock),
gpio_generic_chip_unlock(_T->lock))
DEFINE_LOCK_GUARD_1(gpio_generic_lock_irqsave,
struct gpio_generic_chip,
gpio_generic_chip_lock_irqsave(_T->lock, _T->flags),
gpio_generic_chip_unlock_irqrestore(_T->lock, _T->flags),
unsigned long flags)
#endif /* __LINUX_GPIO_GENERIC_H */