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Message-Id: <20250624-gpio-mmio-rework-v1-1-aea12209d258@linaro.org>
Date: Tue, 24 Jun 2025 15:27:33 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Linus Walleij <linus.walleij@...aro.org>,
Bartosz Golaszewski <brgl@...ev.pl>, Shawn Guo <shawnguo@...nel.org>,
Sascha Hauer <s.hauer@...gutronix.de>,
Pengutronix Kernel Team <kernel@...gutronix.de>,
Fabio Estevam <festevam@...il.com>
Cc: linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: [PATCH 1/8] gpio: generic: add new generic GPIO chip API
From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
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.
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
---
include/linux/gpio/generic.h | 120 +++++++++++++++++++++++++++++++++++++++++++
1 file changed, 120 insertions(+)
diff --git a/include/linux/gpio/generic.h b/include/linux/gpio/generic.h
new file mode 100644
index 0000000000000000000000000000000000000000..b511acd58ab0099b727bf929b7a4e9f9836cd5bc
--- /dev/null
+++ b/include/linux/gpio/generic.h
@@ -0,0 +1,120 @@
+/* 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 */
--
2.48.1
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