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Subject[PATCH v3 5/7] gpio: Add GPIO Aggregator/Repeater driver
Date
GPIO controllers are exported to userspace using /dev/gpiochip*
character devices. Access control to these devices is provided by
standard UNIX file system permissions, on an all-or-nothing basis:
either a GPIO controller is accessible for a user, or it is not.
Currently no mechanism exists to control access to individual GPIOs.

Hence add a GPIO driver to aggregate existing GPIOs, and expose them as
a new gpiochip.

This supports the following use cases:
1. Aggregating GPIOs using Sysfs
This is useful for implementing access control, and assigning a set
of GPIOs to a specific user or virtual machine.

2. GPIO Repeater in Device Tree
This supports modelling e.g. GPIO inverters in DT.

3. Generic GPIO Driver
This provides userspace access to a simple GPIO-operated device
described in DT, cfr. e.g. spidev for SPI-operated devices.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
v3:
- Absorb GPIO forwarder,
- Integrate GPIO Repeater and Generic GPIO driver functionality,
- Use the aggregator parameters to create a GPIO lookup table instead
of an array of GPIO descriptors, which allows to simplify the code:
1. This removes the need for calling gpio_name_to_desc(),
gpiochip_find(), gpiochip_get_desc(), and gpiod_request(),
2. This allows the platform device to always use
devm_gpiod_get_index(), regardless of the origin of the GPIOs,
- Move parameter parsing from platform device probe to sysfs attribute
store, removing the need for platform data passing,
- Use more devm_*() functions to simplify cleanup,
- Add pr_fmt(),
- General refactoring.

v2:
- Add missing initialization of i in gpio_virt_agg_probe(),
- Update for removed .need_valid_mask field and changed
.init_valid_mask() signature,
- Drop "virtual", rename to gpio-aggregator,
- Drop bogus FIXME related to gpiod_set_transitory() expectations,
- Use new GPIO Forwarder Helper,
- Lift limit on the maximum number of GPIOs,
- Improve parsing:
- add support for specifying GPIOs by line name,
- add support for specifying GPIO chips by ID,
- add support for GPIO offset ranges,
- names and offset specifiers must be separated by whitespace,
- GPIO offsets must separated by spaces,
- Use str_has_prefix() and kstrtouint().
---
drivers/gpio/Kconfig | 13 +
drivers/gpio/Makefile | 1 +
drivers/gpio/gpio-aggregator.c | 587 +++++++++++++++++++++++++++++++++
3 files changed, 601 insertions(+)
create mode 100644 drivers/gpio/gpio-aggregator.c

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 8adffd42f8cb0559..36b6b57a6b05e906 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1507,6 +1507,19 @@ config GPIO_VIPERBOARD

endmenu

+config GPIO_AGGREGATOR
+ tristate "GPIO Aggregator/Repeater"
+ help
+ Say yes here to enable the GPIO Aggregator and repeater, which
+ provides a way to aggregate and/or repeat existing GPIOs into a new
+ GPIO device.
+ This can serve the following purposes:
+ 1. Assign a collection of GPIOs to a user, or export them to a
+ virtual machine,
+ 2. Support GPIOs that are connected to a physical inverter,
+ 3. Provide a generic driver for a GPIO-operated device, to be
+ controlled from userspace using the GPIO chardev interface.
+
config GPIO_MOCKUP
tristate "GPIO Testing Driver"
select IRQ_SIM
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 34eb8b2b12dd656c..f9971eeb1f32335f 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -25,6 +25,7 @@ obj-$(CONFIG_GPIO_74XX_MMIO) += gpio-74xx-mmio.o
obj-$(CONFIG_GPIO_ADNP) += gpio-adnp.o
obj-$(CONFIG_GPIO_ADP5520) += gpio-adp5520.o
obj-$(CONFIG_GPIO_ADP5588) += gpio-adp5588.o
+obj-$(CONFIG_GPIO_AGGREGATOR) += gpio-aggregator.o
obj-$(CONFIG_GPIO_ALTERA_A10SR) += gpio-altera-a10sr.o
obj-$(CONFIG_GPIO_ALTERA) += gpio-altera.o
obj-$(CONFIG_GPIO_AMD8111) += gpio-amd8111.o
diff --git a/drivers/gpio/gpio-aggregator.c b/drivers/gpio/gpio-aggregator.c
new file mode 100644
index 0000000000000000..873578c6f9683db8
--- /dev/null
+++ b/drivers/gpio/gpio-aggregator.c
@@ -0,0 +1,587 @@
+// SPDX-License-Identifier: GPL-2.0-only
+//
+// GPIO Aggregator and Repeater
+//
+// Copyright (C) 2019 Glider bvba
+
+#define DRV_NAME "gpio-aggregator"
+#define pr_fmt(fmt) DRV_NAME ": " fmt
+
+#include <linux/bitmap.h>
+#include <linux/bitops.h>
+#include <linux/ctype.h>
+#include <linux/gpio/driver.h>
+#include <linux/gpio/machine.h>
+#include <linux/idr.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/overflow.h>
+#include <linux/platform_device.h>
+#include <linux/spinlock.h>
+#include <linux/string.h>
+
+#include "gpiolib.h"
+
+
+ /*
+ * GPIO Aggregator sysfs interface
+ */
+
+struct gpio_aggregator {
+ struct gpiod_lookup_table *lookups;
+ struct platform_device *pdev;
+ char args[];
+};
+
+static DEFINE_MUTEX(gpio_aggregator_lock); /* protects idr */
+static DEFINE_IDR(gpio_aggregator_idr);
+
+static char *get_arg(char **args)
+{
+ char *start = *args, *end;
+
+ while (isspace(*start))
+ start++;
+
+ if (!*start)
+ return NULL;
+
+ if (*start == '"') {
+ /* Quoted arg */
+ end = strchr(++start, '"');
+ if (!end)
+ return ERR_PTR(-EINVAL);
+ } else {
+ /* Unquoted arg */
+ for (end = start; *end && !isspace(*end); end++) ;
+ }
+
+ if (*end)
+ *end++ = '\0';
+
+ *args = end;
+ return start;
+}
+
+static bool isrange(const char *s)
+{
+ size_t n = strlen(s);
+
+ if (IS_ERR_OR_NULL(s))
+ return false;
+
+ while (1) {
+ n = strspn(s, "0123456789");
+ if (!n)
+ return false;
+
+ s += n;
+
+ switch (*s++) {
+ case '\0':
+ return true;
+
+ case '-':
+ case ',':
+ break;
+
+ default:
+ return false;
+ }
+ }
+}
+
+static int aggr_add_gpio(struct gpio_aggregator *aggr, const char *label,
+ int hwnum, unsigned int *n)
+{
+ struct gpiod_lookup_table *lookups;
+
+ lookups = krealloc(aggr->lookups, struct_size(lookups, table, *n + 2),
+ GFP_KERNEL);
+ if (!lookups)
+ return -ENOMEM;
+
+ lookups->table[*n].chip_label = label;
+ lookups->table[*n].chip_hwnum = hwnum;
+ lookups->table[*n].idx = *n;
+
+ (*n)++;
+ memset(&lookups->table[*n], 0, sizeof(lookups->table[*n]));
+
+ aggr->lookups = lookups;
+ return 0;
+}
+
+static int aggr_parse(struct gpio_aggregator *aggr)
+{
+ char *name, *offsets, *first, *last, *next;
+ unsigned int a, b, i, n = 0;
+ char *args = aggr->args;
+ int error;
+
+ for (name = get_arg(&args), offsets = get_arg(&args); name;
+ offsets = get_arg(&args)) {
+ if (IS_ERR(name)) {
+ pr_err("Cannot get GPIO specifier: %ld\n",
+ PTR_ERR(name));
+ return PTR_ERR(name);
+ }
+
+ if (!isrange(offsets)) {
+ /* Named GPIO line */
+ error = aggr_add_gpio(aggr, name, -1, &n);
+ if (error)
+ return error;
+
+ name = offsets;
+ continue;
+ }
+
+ /* GPIO chip + offset(s) */
+ for (first = offsets; *first; first = next) {
+ next = strchrnul(first, ',');
+ if (*next)
+ *next++ = '\0';
+
+ last = strchr(first, '-');
+ if (last)
+ *last++ = '\0';
+
+ if (kstrtouint(first, 10, &a)) {
+ pr_err("Cannot parse GPIO index %s\n", first);
+ return -EINVAL;
+ }
+
+ if (!last) {
+ b = a;
+ } else if (kstrtouint(last, 10, &b)) {
+ pr_err("Cannot parse GPIO index %s\n", last);
+ return -EINVAL;
+ }
+
+ for (i = a; i <= b; i++) {
+ error = aggr_add_gpio(aggr, name, i, &n);
+ if (error)
+ return error;
+ }
+ }
+
+ name = get_arg(&args);
+ }
+
+ if (!n) {
+ pr_err("No GPIOs specified\n");
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static ssize_t new_device_store(struct device_driver *driver, const char *buf,
+ size_t count)
+{
+ struct gpio_aggregator *aggr;
+ struct platform_device *pdev;
+ int res, id;
+
+ /* kernfs guarantees string termination, so count + 1 is safe */
+ aggr = kzalloc(sizeof(*aggr) + count + 1, GFP_KERNEL);
+ if (!aggr)
+ return -ENOMEM;
+
+ memcpy(aggr->args, buf, count + 1);
+
+ aggr->lookups = kzalloc(struct_size(aggr->lookups, table, 1),
+ GFP_KERNEL);
+ if (!aggr->lookups) {
+ res = -ENOMEM;
+ goto free_ga;
+ }
+
+ mutex_lock(&gpio_aggregator_lock);
+ id = idr_alloc(&gpio_aggregator_idr, aggr, 0, 0, GFP_KERNEL);
+ mutex_unlock(&gpio_aggregator_lock);
+
+ if (id < 0) {
+ res = id;
+ goto free_table;
+ }
+
+ aggr->lookups->dev_id = kasprintf(GFP_KERNEL, "%s.%d", DRV_NAME, id);
+ if (!aggr->lookups) {
+ res = -ENOMEM;
+ goto remove_idr;
+ }
+
+ res = aggr_parse(aggr);
+ if (res)
+ goto free_dev_id;
+
+ gpiod_add_lookup_table(aggr->lookups);
+
+ pdev = platform_device_register_simple(DRV_NAME, id, NULL, 0);
+ if (IS_ERR(pdev)) {
+ res = PTR_ERR(pdev);
+ goto remove_table;
+ }
+
+ aggr->pdev = pdev;
+ return count;
+
+remove_table:
+ gpiod_remove_lookup_table(aggr->lookups);
+free_dev_id:
+ kfree(aggr->lookups->dev_id);
+remove_idr:
+ mutex_lock(&gpio_aggregator_lock);
+ idr_remove(&gpio_aggregator_idr, id);
+ mutex_unlock(&gpio_aggregator_lock);
+free_table:
+ kfree(aggr->lookups);
+free_ga:
+ kfree(aggr);
+ return res;
+}
+
+static DRIVER_ATTR_WO(new_device);
+
+static void gpio_aggregator_free(struct gpio_aggregator *aggr)
+{
+ platform_device_unregister(aggr->pdev);
+ gpiod_remove_lookup_table(aggr->lookups);
+ kfree(aggr->lookups->dev_id);
+ kfree(aggr->lookups);
+ kfree(aggr);
+}
+
+static ssize_t delete_device_store(struct device_driver *driver,
+ const char *buf, size_t count)
+{
+ struct gpio_aggregator *aggr;
+ unsigned int id;
+ int error;
+
+ if (!str_has_prefix(buf, DRV_NAME "."))
+ return -EINVAL;
+
+ error = kstrtouint(buf + strlen(DRV_NAME "."), 10, &id);
+ if (error)
+ return error;
+
+ mutex_lock(&gpio_aggregator_lock);
+ aggr = idr_remove(&gpio_aggregator_idr, id);
+ mutex_unlock(&gpio_aggregator_lock);
+ if (!aggr)
+ return -ENOENT;
+
+ gpio_aggregator_free(aggr);
+ return count;
+}
+static DRIVER_ATTR_WO(delete_device);
+
+static struct attribute *gpio_aggregator_attrs[] = {
+ &driver_attr_new_device.attr,
+ &driver_attr_delete_device.attr,
+ NULL,
+};
+ATTRIBUTE_GROUPS(gpio_aggregator);
+
+static int __exit gpio_aggregator_idr_remove(int id, void *p, void *data)
+{
+ gpio_aggregator_free(p);
+ return 0;
+}
+
+static void __exit gpio_aggregator_remove_all(void)
+{
+ mutex_lock(&gpio_aggregator_lock);
+ idr_for_each(&gpio_aggregator_idr, gpio_aggregator_idr_remove, NULL);
+ idr_destroy(&gpio_aggregator_idr);
+ mutex_unlock(&gpio_aggregator_lock);
+}
+
+
+ /*
+ * Common GPIO Forwarder
+ */
+
+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
+ * @dev: 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.
+ */
+static struct gpiochip_fwd *gpiochip_fwd_create(struct device *dev,
+ unsigned int ngpios,
+ struct gpio_desc *descs[])
+{
+ const char *label = dev_name(dev);
+ struct gpiochip_fwd *fwd;
+ struct gpio_chip *chip;
+ unsigned int i;
+ int error;
+
+ fwd = devm_kzalloc(dev, 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++) {
+ dev_dbg(dev, "gpio %u => gpio-%d (%s)\n", i,
+ desc_to_gpio(descs[i]), descs[i]->label ? : "?");
+
+ 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 = dev;
+ 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 = devm_gpiochip_add_data(dev, chip, fwd);
+ if (error)
+ return ERR_PTR(error);
+
+ return fwd;
+}
+
+
+ /*
+ * Common GPIO Aggregator/Repeater platform device
+ */
+
+static int gpio_aggregator_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct gpio_desc **descs;
+ struct gpiochip_fwd *fwd;
+ int i, n;
+
+ n = gpiod_count(dev, NULL);
+ if (n < 0)
+ return n;
+
+ descs = devm_kmalloc_array(dev, n, sizeof(*descs), GFP_KERNEL);
+ if (!descs)
+ return -ENOMEM;
+
+ for (i = 0; i < n; i++) {
+ descs[i] = devm_gpiod_get_index(dev, NULL, i, GPIOD_ASIS);
+ if (IS_ERR(descs[i]))
+ return PTR_ERR(descs[i]);
+ }
+
+ fwd = gpiochip_fwd_create(dev, n, descs);
+ if (IS_ERR(fwd))
+ return PTR_ERR(fwd);
+
+ platform_set_drvdata(pdev, fwd);
+ return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id gpio_aggregator_dt_ids[] = {
+ { .compatible = "gpio-repeater" },
+ /*
+ * Add GPIO-operated devices controlled from userspace below,
+ * or use "driver_override" in sysfs
+ */
+ {},
+};
+MODULE_DEVICE_TABLE(of, gpio_aggregator_dt_ids);
+#endif
+
+static struct platform_driver gpio_aggregator_driver = {
+ .probe = gpio_aggregator_probe,
+ .driver = {
+ .name = DRV_NAME,
+ .groups = gpio_aggregator_groups,
+ .of_match_table = of_match_ptr(gpio_aggregator_dt_ids),
+ },
+};
+
+static int __init gpio_aggregator_init(void)
+{
+ return platform_driver_register(&gpio_aggregator_driver);
+}
+module_init(gpio_aggregator_init);
+
+static void __exit gpio_aggregator_exit(void)
+{
+ gpio_aggregator_remove_all();
+ platform_driver_unregister(&gpio_aggregator_driver);
+}
+module_exit(gpio_aggregator_exit);
+
+MODULE_AUTHOR("Geert Uytterhoeven <geert+renesas@glider.be>");
+MODULE_DESCRIPTION("GPIO Aggregator/Repeater");
+MODULE_LICENSE("GPL v2");
--
2.17.1
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