iio: Add support for creating IIO devices via configfs

This is similar with support for creating triggers via configfs.
Devices will be hosted under:
	* /config/iio/devices

We allow users to register "device types" under:
	* /config/iio/devices/<device_types>/

Signed-off-by: Daniel Baluta <daniel.baluta@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

3 files changed, 191 insertions, 0 deletions

diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
index 505e921f0b19..6743b18194fb 100644
--- a/drivers/iio/Kconfig
+++ b/drivers/iio/Kconfig
@@ -46,6 +46,14 @@ config IIO_CONSUMERS_PER_TRIGGER
         This value controls the maximum number of consumers that a
         given trigger may handle. Default is 2.
 
+config IIO_SW_DEVICE
+        tristate "Enable software IIO device support"
+        select IIO_CONFIGFS
+        help
+         Provides IIO core support for software devices. A software
+         device can be created via configfs or directly by a driver
+         using the API provided.
+
 config IIO_SW_TRIGGER
         tristate "Enable software triggers support"
         select IIO_CONFIGFS
diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
index 20f649073462..87e4c4369e2f 100644
--- a/drivers/iio/Makefile
+++ b/drivers/iio/Makefile
@@ -8,6 +8,7 @@ industrialio-$(CONFIG_IIO_BUFFER) += industrialio-buffer.o
 industrialio-$(CONFIG_IIO_TRIGGER) += industrialio-trigger.o
 
 obj-$(CONFIG_IIO_CONFIGFS) += industrialio-configfs.o
+obj-$(CONFIG_IIO_SW_DEVICE) += industrialio-sw-device.o
 obj-$(CONFIG_IIO_SW_TRIGGER) += industrialio-sw-trigger.o
 obj-$(CONFIG_IIO_TRIGGERED_EVENT) += industrialio-triggered-event.o
 
diff --git a/drivers/iio/industrialio-sw-device.c b/drivers/iio/industrialio-sw-device.c
new file mode 100644
index 000000000000..81b49cfca452
--- /dev/null
+++ b/drivers/iio/industrialio-sw-device.c
@@ -0,0 +1,182 @@
+/*
+ * The Industrial I/O core, software IIO devices functions
+ *
+ * Copyright (c) 2016 Intel Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kmod.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+
+#include <linux/iio/sw_device.h>
+#include <linux/iio/configfs.h>
+#include <linux/configfs.h>
+
+static struct config_group *iio_devices_group;
+static struct config_item_type iio_device_type_group_type;
+
+static struct config_item_type iio_devices_group_type = {
+        .ct_owner = THIS_MODULE,
+};
+
+static LIST_HEAD(iio_device_types_list);
+static DEFINE_MUTEX(iio_device_types_lock);
+
+static
+struct iio_sw_device_type *__iio_find_sw_device_type(const char *name,
+                                                     unsigned len)
+{
+        struct iio_sw_device_type *d = NULL, *iter;
+
+        list_for_each_entry(iter, &iio_device_types_list, list)
+                if (!strcmp(iter->name, name)) {
+                        d = iter;
+                        break;
+                }
+
+        return d;
+}
+
+int iio_register_sw_device_type(struct iio_sw_device_type *d)
+{
+        struct iio_sw_device_type *iter;
+        int ret = 0;
+
+        mutex_lock(&iio_device_types_lock);
+        iter = __iio_find_sw_device_type(d->name, strlen(d->name));
+        if (iter)
+                ret = -EBUSY;
+        else
+                list_add_tail(&d->list, &iio_device_types_list);
+        mutex_unlock(&iio_device_types_lock);
+
+        if (ret)
+                return ret;
+
+        d->group = configfs_register_default_group(iio_devices_group, d->name,
+                                                &iio_device_type_group_type);
+        if (IS_ERR(d->group))
+                ret = PTR_ERR(d->group);
+
+        return ret;
+}
+EXPORT_SYMBOL(iio_register_sw_device_type);
+
+void iio_unregister_sw_device_type(struct iio_sw_device_type *dt)
+{
+        struct iio_sw_device_type *iter;
+
+        mutex_lock(&iio_device_types_lock);
+        iter = __iio_find_sw_device_type(dt->name, strlen(dt->name));
+        if (iter)
+                list_del(&dt->list);
+        mutex_unlock(&iio_device_types_lock);
+
+        configfs_unregister_default_group(dt->group);
+}
+EXPORT_SYMBOL(iio_unregister_sw_device_type);
+
+static
+struct iio_sw_device_type *iio_get_sw_device_type(const char *name)
+{
+        struct iio_sw_device_type *dt;
+
+        mutex_lock(&iio_device_types_lock);
+        dt = __iio_find_sw_device_type(name, strlen(name));
+        if (dt && !try_module_get(dt->owner))
+                dt = NULL;
+        mutex_unlock(&iio_device_types_lock);
+
+        return dt;
+}
+
+struct iio_sw_device *iio_sw_device_create(const char *type, const char *name)
+{
+        struct iio_sw_device *d;
+        struct iio_sw_device_type *dt;
+
+        dt = iio_get_sw_device_type(type);
+        if (!dt) {
+                pr_err("Invalid device type: %s\n", type);
+                return ERR_PTR(-EINVAL);
+        }
+        d = dt->ops->probe(name);
+        if (IS_ERR(d))
+                goto out_module_put;
+
+        d->device_type = dt;
+
+        return d;
+out_module_put:
+        module_put(dt->owner);
+        return d;
+}
+EXPORT_SYMBOL(iio_sw_device_create);
+
+void iio_sw_device_destroy(struct iio_sw_device *d)
+{
+        struct iio_sw_device_type *dt = d->device_type;
+
+        dt->ops->remove(d);
+        module_put(dt->owner);
+}
+EXPORT_SYMBOL(iio_sw_device_destroy);
+
+static struct config_group *device_make_group(struct config_group *group,
+                                              const char *name)
+{
+        struct iio_sw_device *d;
+
+        d = iio_sw_device_create(group->cg_item.ci_name, name);
+        if (IS_ERR(d))
+                return ERR_CAST(d);
+
+        config_item_set_name(&d->group.cg_item, "%s", name);
+
+        return &d->group;
+}
+
+static void device_drop_group(struct config_group *group,
+                              struct config_item *item)
+{
+        struct iio_sw_device *d = to_iio_sw_device(item);
+
+        iio_sw_device_destroy(d);
+        config_item_put(item);
+}
+
+static struct configfs_group_operations device_ops = {
+        .make_group     = &device_make_group,
+        .drop_item      = &device_drop_group,
+};
+
+static struct config_item_type iio_device_type_group_type = {
+        .ct_group_ops = &device_ops,
+        .ct_owner       = THIS_MODULE,
+};
+
+static int __init iio_sw_device_init(void)
+{
+        iio_devices_group =
+                configfs_register_default_group(&iio_configfs_subsys.su_group,
+                                                "devices",
+                                                &iio_devices_group_type);
+        return PTR_ERR_OR_ZERO(iio_devices_group);
+}
+module_init(iio_sw_device_init);
+
+static void __exit iio_sw_device_exit(void)
+{
+        configfs_unregister_default_group(iio_devices_group);
+}
+module_exit(iio_sw_device_exit);
+
+MODULE_AUTHOR("Daniel Baluta <daniel.baluta@intel.com>");
+MODULE_DESCRIPTION("Industrial I/O software devices support");
+MODULE_LICENSE("GPL v2");