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Subject[PATCH/RFC v2 4/5] gpio: Add GPIO Forwarder Helper
Date
Add a helper for creating GPIO chips that merely forward all operations
to other GPIOs.

This will be used by the GPIO Aggregator.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
I expect this can be used by the GPIO inverter, too, after adding an
"invert" flag, or a filter function that checks which offsets need
inversion.
---
drivers/gpio/Kconfig | 3 +
drivers/gpio/Makefile | 1 +
drivers/gpio/gpiolib-fwd.c | 272 +++++++++++++++++++++++++++++++++++++
drivers/gpio/gpiolib-fwd.h | 16 +++
4 files changed, 292 insertions(+)
create mode 100644 drivers/gpio/gpiolib-fwd.c
create mode 100644 drivers/gpio/gpiolib-fwd.h

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 38e096e6925fa65d..29d3ce8debcca1f6 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -47,6 +47,9 @@ config GPIOLIB_IRQCHIP
select IRQ_DOMAIN
bool

+config GPIOLIB_FWD
+ tristate
+
config DEBUG_GPIO
bool "Debug GPIO calls"
depends on DEBUG_KERNEL
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index d2fd19c15bae3fba..8a0e685c92b69855 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -10,6 +10,7 @@ obj-$(CONFIG_GPIOLIB) += gpiolib-devprop.o
obj-$(CONFIG_OF_GPIO) += gpiolib-of.o
obj-$(CONFIG_GPIO_SYSFS) += gpiolib-sysfs.o
obj-$(CONFIG_GPIO_ACPI) += gpiolib-acpi.o
+obj-$(CONFIG_GPIOLIB_FWD) += gpiolib-fwd.o

# Device drivers. Generally keep list sorted alphabetically
obj-$(CONFIG_GPIO_GENERIC) += gpio-generic.o
diff --git a/drivers/gpio/gpiolib-fwd.c b/drivers/gpio/gpiolib-fwd.c
new file mode 100644
index 0000000000000000..28dac8c60a981337
--- /dev/null
+++ b/drivers/gpio/gpiolib-fwd.c
@@ -0,0 +1,272 @@
+// SPDX-License-Identifier: GPL-2.0-only
+//
+// GPIO Forwarder Helper
+//
+// Copyright (C) 2019 Glider bvba
+
+#include <linux/bitmap.h>
+#include <linux/bitops.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/overflow.h>
+#include <linux/spinlock.h>
+
+#include "gpiolib.h"
+#include "gpiolib-fwd.h"
+
+struct gpiochip_fwd {
+ struct gpio_chip chip;
+ struct gpio_desc **descs;
+ union {
+ struct mutex mlock; /* protects tmp[] if can_sleep */
+ spinlock_t slock; /* protects tmp[] if !can_sleep */
+ };
+ unsigned long tmp[]; /* values and descs for multiple ops */
+};
+
+static int gpio_fwd_get_direction(struct gpio_chip *chip, unsigned int offset)
+{
+ struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
+
+ return gpiod_get_direction(fwd->descs[offset]);
+}
+
+static int gpio_fwd_direction_input(struct gpio_chip *chip, unsigned int offset)
+{
+ struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
+
+ return gpiod_direction_input(fwd->descs[offset]);
+}
+
+static int gpio_fwd_direction_output(struct gpio_chip *chip,
+ unsigned int offset, int value)
+{
+ struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
+
+ return gpiod_direction_output(fwd->descs[offset], value);
+}
+
+static int gpio_fwd_get(struct gpio_chip *chip, unsigned int offset)
+{
+ struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
+
+ return gpiod_get_value(fwd->descs[offset]);
+}
+
+static int gpio_fwd_get_multiple(struct gpio_chip *chip, unsigned long *mask,
+ unsigned long *bits)
+{
+ struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
+ unsigned long *values, flags;
+ struct gpio_desc **descs;
+ unsigned int i, j = 0;
+ int error;
+
+ if (chip->can_sleep)
+ mutex_lock(&fwd->mlock);
+ else
+ spin_lock_irqsave(&fwd->slock, flags);
+
+ values = &fwd->tmp[0];
+ bitmap_clear(values, 0, fwd->chip.ngpio);
+ descs = (void *)&fwd->tmp[BITS_TO_LONGS(fwd->chip.ngpio)];
+
+ for_each_set_bit(i, mask, fwd->chip.ngpio)
+ descs[j++] = fwd->descs[i];
+
+ error = gpiod_get_array_value(j, descs, NULL, values);
+ if (!error) {
+ j = 0;
+ for_each_set_bit(i, mask, fwd->chip.ngpio)
+ __assign_bit(i, bits, test_bit(j++, values));
+ }
+
+ if (chip->can_sleep)
+ mutex_unlock(&fwd->mlock);
+ else
+ spin_unlock_irqrestore(&fwd->slock, flags);
+
+ return error;
+}
+
+static void gpio_fwd_set(struct gpio_chip *chip, unsigned int offset, int value)
+{
+ struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
+
+ gpiod_set_value(fwd->descs[offset], value);
+}
+
+static void gpio_fwd_set_multiple(struct gpio_chip *chip, unsigned long *mask,
+ unsigned long *bits)
+{
+ struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
+ unsigned long *values, flags;
+ struct gpio_desc **descs;
+ unsigned int i, j = 0;
+
+ if (chip->can_sleep)
+ mutex_lock(&fwd->mlock);
+ else
+ spin_lock_irqsave(&fwd->slock, flags);
+
+ values = &fwd->tmp[0];
+ descs = (void *)&fwd->tmp[BITS_TO_LONGS(fwd->chip.ngpio)];
+
+ for_each_set_bit(i, mask, fwd->chip.ngpio) {
+ __assign_bit(j, values, test_bit(i, bits));
+ descs[j++] = fwd->descs[i];
+ }
+
+ gpiod_set_array_value(j, descs, NULL, values);
+
+ if (chip->can_sleep)
+ mutex_unlock(&fwd->mlock);
+ else
+ spin_unlock_irqrestore(&fwd->slock, flags);
+}
+
+static int gpio_fwd_set_config(struct gpio_chip *chip, unsigned int offset,
+ unsigned long config)
+{
+ struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
+
+ chip = fwd->descs[offset]->gdev->chip;
+ if (chip->set_config)
+ return chip->set_config(chip, offset, config);
+
+ return -ENOTSUPP;
+}
+
+static int gpio_fwd_init_valid_mask(struct gpio_chip *chip,
+ unsigned long *valid_mask,
+ unsigned int ngpios)
+{
+ struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
+ unsigned int i;
+
+ for (i = 0; i < ngpios; i++) {
+ if (!gpiochip_line_is_valid(fwd->descs[i]->gdev->chip,
+ gpio_chip_hwgpio(fwd->descs[i])))
+ clear_bit(i, valid_mask);
+ }
+
+ return 0;
+}
+
+/**
+ * gpiochip_fwd_create() - Create a new GPIO forwarder
+ * @label: Name of the forwarder
+ * @parent: Optional parent device pointer
+ * @ngpios: Number of GPIOs in the forwarder.
+ * @descs: Array containing the GPIO descriptors to forward to.
+ * This array must contain @ngpios entries, and must not be deallocated
+ * before the forwarder has been destroyed again.
+ *
+ * This function creates a new gpiochip, which forwards all GPIO operations to
+ * the passed GPIO descriptors.
+ *
+ * Return: An opaque object pointer, or an ERR_PTR()-encoded negative error
+ * code on failure.
+ */
+struct gpiochip_fwd *gpiochip_fwd_create(const char *label,
+ struct device *parent,
+ unsigned int ngpios,
+ struct gpio_desc *descs[])
+{
+ struct gpiochip_fwd *fwd;
+ struct gpio_chip *chip;
+ unsigned int i;
+ int error;
+
+ fwd = kzalloc(struct_size(fwd, tmp, BITS_TO_LONGS(ngpios) + ngpios),
+ GFP_KERNEL);
+ if (!fwd)
+ return ERR_PTR(-ENOMEM);
+
+ chip = &fwd->chip;
+
+ for (i = 0; i < ngpios; i++) {
+ pr_debug("%s: gpio %u => gpio-%d (%s)\n", label, i,
+ desc_to_gpio(descs[i]), descs[i]->label ? : "?");
+
+ error = gpiod_request(descs[i], label);
+ if (error) {
+ gpiod_err(descs[i], "%s: Cannot request GPIO: %d\n",
+ label, error);
+ goto free;
+ }
+
+ if (gpiod_cansleep(descs[i]))
+ chip->can_sleep = true;
+ if (descs[i]->gdev->chip->set_config)
+ chip->set_config = gpio_fwd_set_config;
+ if (descs[i]->gdev->chip->init_valid_mask)
+ chip->init_valid_mask = gpio_fwd_init_valid_mask;
+ }
+
+ chip->label = label;
+ chip->parent = parent;
+ chip->owner = THIS_MODULE;
+ chip->get_direction = gpio_fwd_get_direction;
+ chip->direction_input = gpio_fwd_direction_input;
+ chip->direction_output = gpio_fwd_direction_output;
+ chip->get = gpio_fwd_get;
+ chip->get_multiple = gpio_fwd_get_multiple;
+ chip->set = gpio_fwd_set;
+ chip->set_multiple = gpio_fwd_set_multiple;
+ chip->base = -1;
+ chip->ngpio = ngpios;
+ fwd->descs = descs;
+
+ if (chip->can_sleep)
+ mutex_init(&fwd->mlock);
+ else
+ spin_lock_init(&fwd->slock);
+
+ error = gpiochip_add_data(chip, fwd);
+ if (error)
+ goto free;
+
+ return fwd;
+
+free:
+ while (i-- > 0)
+ gpiod_free(descs[i]);
+
+ kfree(fwd);
+
+ return ERR_PTR(error);
+}
+EXPORT_SYMBOL_GPL(gpiochip_fwd_create);
+
+/**
+ * gpiochip_fwd_destroy() - Destroy a new GPIO forwarder
+ * @fwd: Opaque object pointer, as returned by gpiochip_fwd_create()
+ *
+ * This function destroys GPIO forwarder gpiochip, previously created by
+ * gpiochip_fwd_create().
+
+ * Return: Zero.
+ */
+int gpiochip_fwd_destroy(struct gpiochip_fwd *fwd)
+{
+ unsigned int i;
+
+ if (IS_ERR_OR_NULL(fwd))
+ return 0;
+
+ gpiochip_remove(&fwd->chip);
+
+ for (i = 0; i < fwd->chip.ngpio; i++)
+ gpiod_free(fwd->descs[i]);
+
+ kfree(fwd);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(gpiochip_fwd_destroy);
+
+MODULE_AUTHOR("Geert Uytterhoeven <geert+renesas@glider.be>");
+MODULE_DESCRIPTION("GPIO Forwarder Helper");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/gpio/gpiolib-fwd.h b/drivers/gpio/gpiolib-fwd.h
new file mode 100644
index 0000000000000000..68d299afc6883a9c
--- /dev/null
+++ b/drivers/gpio/gpiolib-fwd.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * GPIO Forwarder Helper
+ *
+ * Copyright (C) 2019 Glider bvba
+ */
+
+struct device;
+struct gpio_desc;
+struct gpiochip_fwd;
+
+struct gpiochip_fwd *gpiochip_fwd_create(const char *label,
+ struct device *parent,
+ unsigned int ngpios,
+ struct gpio_desc *descs[]);
+int gpiochip_fwd_destroy(struct gpiochip_fwd *fwd);
--
2.17.1
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