Selected GPIOs (defined as child nodes in DT) may be exported as symlinks to user space (using gpiod_export_link())
The advantages of this are: * Userspace no longer needs to know the GPIO number (which may vary with other hardware and with kernel version due to dynamic allocation) * Userspace can be prevented from changing the direction if that does not make sense from a hardware perspective. Signed-off-by: Martin Fuzzey <[email protected]> --- drivers/gpio/Kconfig | 9 ++ drivers/gpio/Makefile | 1 drivers/gpio/gpio-exporter.c | 171 ++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 181 insertions(+) create mode 100644 drivers/gpio/gpio-exporter.c diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig index 633ec21..682fce2 100644 --- a/drivers/gpio/Kconfig +++ b/drivers/gpio/Kconfig @@ -110,6 +110,15 @@ config GPIO_DA9055 config GPIO_MAX730X tristate +config GPIO_EXPORTER + tristate "Userspace exporter driver" + depends on OF_GPIO && GPIO_SYSFS + help + This enables a GPIO consumer which exports some GPIOs to userspace. + The GPIOs to be exported are defined in the device tree. + The exported GPIOs are represented as symbolic links in sysfs, + relieving usespace of the burden of knowing the GPIO number to export + comment "Memory mapped GPIO drivers:" config GPIO_74XX_MMIO diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile index 81755f1..bb665c5 100644 --- a/drivers/gpio/Makefile +++ b/drivers/gpio/Makefile @@ -10,6 +10,7 @@ obj-$(CONFIG_GPIO_SYSFS) += gpiolib-sysfs.o obj-$(CONFIG_GPIO_ACPI) += gpiolib-acpi.o # Device drivers. Generally keep list sorted alphabetically +obj-$(CONFIG_GPIO_EXPORTER) += gpio-exporter.o obj-$(CONFIG_GPIO_GENERIC) += gpio-generic.o obj-$(CONFIG_GPIO_74X164) += gpio-74x164.o diff --git a/drivers/gpio/gpio-exporter.c b/drivers/gpio/gpio-exporter.c new file mode 100644 index 0000000..72cdcf0 --- /dev/null +++ b/drivers/gpio/gpio-exporter.c @@ -0,0 +1,171 @@ +/* + * A driver that allows some gpios to be exported to userspace + * using friendly names. + * + * This allows the gpios to be exported to be configured in the device tree + * and frees userspace from having to know unstable gpio numbers. + * + * Copyright 2015 Parkeon + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License as + * published by the Free Software Foundation; either version 2 of the + * License, or (at your option) any later version. + * + */ + +#include <linux/device.h> +#include <linux/err.h> +#include <linux/gpio/consumer.h> +#include <linux/module.h> +#include <linux/of.h> +#include <linux/of_device.h> +#include <linux/platform_device.h> + + +struct gpio_exporter_gpio { + const char *name; + struct gpio_desc *desc; +}; + +struct gpio_exporter_data { + struct device *dev; + int num_gpios; + struct gpio_exporter_gpio *gpios; +}; + +static int gpio_exporter_do_one(struct gpio_exporter_data *data, + struct fwnode_handle *child) +{ + struct device_node *np = of_node(child); + const char *name = np->name; + const char *config; + struct gpio_desc *desc; + int ret; + + desc = devm_get_gpiod_from_child(data->dev, child); + if (IS_ERR(desc)) { + ret = PTR_ERR(desc); + goto failed_get; + } + + if (of_property_read_bool(np, "output")) { + u32 state = 0; + + of_property_read_u32(np, "initial-state", &state); + ret = gpiod_direction_output(desc, state); + } else { + ret = gpiod_direction_input(desc); + } + if (ret) + goto failed_setdir; + + ret = gpiod_export(desc, + of_property_read_bool(np, "allow-direction-change")); + if (ret) + goto failed_export; + + ret = gpiod_export_link(data->dev, name, desc); + if (ret) + goto failed_link; + + data->gpios[data->num_gpios].name = name; + data->gpios[data->num_gpios].desc = desc; + data->num_gpios++; + + dev_info(data->dev, + "Exported gpio%d as '%s'\n", desc_to_gpio(desc), name); + + return 0; + +failed_link: + gpiod_unexport(desc); + +failed_export: +failed_setdir: +failed_get: + dev_err(data->dev, "Failed to export gpio '%s': %d\n", name, ret); + + return ret; +} + +static void gpio_exporter_cleanup(struct gpio_exporter_data *data) +{ + int i; + + for (i = 0; i < data->num_gpios; i++) { + sysfs_remove_link(&data->dev->kobj, data->gpios[i].name); + gpiod_unexport(data->gpios[i].desc); + } +} + +static int gpio_exporter_probe(struct platform_device *pdev) +{ + struct device *dev = &pdev->dev; + struct fwnode_handle *child; + int num_gpios; + int ret; + struct gpio_exporter_data *data; + + if (!dev->of_node) + return -ENODEV; + + data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL); + if (!data) + return -ENOMEM; + + data->dev = dev; + dev_set_drvdata(dev, data); + + num_gpios = device_get_child_node_count(dev); + data->gpios = devm_kzalloc(dev, num_gpios * sizeof(*data->gpios), + GFP_KERNEL); + if (!data->gpios) + return -ENOMEM; + + device_for_each_child_node(dev, child) { + ret = gpio_exporter_do_one(data, child); + if (ret) + goto out_cleanup; + } + + dev_info(dev, "exported %d gpios\n", data->num_gpios); + + return 0; + +out_cleanup: + gpio_exporter_cleanup(data); + + return ret; +} + +static int gpio_exporter_remove(struct platform_device *pdev) +{ + struct gpio_exporter_data *data = platform_get_drvdata(pdev); + + gpio_exporter_cleanup(data); + + return 0; +} + +static const struct of_device_id gpio_exporter_dt_ids[] = { + { .compatible = "linux,gpio-exporter", }, + { /* sentinel */ } +}; +MODULE_DEVICE_TABLE(of, gpio_exporter_dt_ids); + +static struct platform_driver gpio_exporter_driver = { + .driver = { + .name = "gpio-exporter", + .of_match_table = gpio_exporter_dt_ids, + }, + .probe = gpio_exporter_probe, + .remove = gpio_exporter_remove, +}; + +module_platform_driver(gpio_exporter_driver); + +MODULE_LICENSE("GPL v2"); +MODULE_AUTHOR("Martin Fuzzey <[email protected]>"); +MODULE_DESCRIPTION("Userspace GPIO exporter"); +MODULE_ALIAS("platform:gpio-exporter"); -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
