[PATCH v2 1/3] iio: configfs: Add configfs support to IIO

[Daniel Baluta <daniel.baluta@intel.com>]

This module is the core of IIO configfs. It creates the "iio" subsystem under
configfs mount point root, with one default group for "triggers".

It offers basic interface for registering software trigger types. Next patches
will add "hrtimer" and "sysfs" trigger types. To add a new trigger type we must
create a new kernel module which implements iio_configfs_trigger.h interface.

See Documentation/iio/iio_configfs.txt for more details on how configfs
support for IIO works.

Signed-off-by: Daniel Baluta <daniel.baluta@intel.com>
---
Changes since v1:
	* addressed feedback from v1:
		* https://lkml.org/lkml/2015/3/25/647
	* create a directory per trigger type
	* removed activate and type attributes

 drivers/iio/Kconfig                      |   8 ++
 drivers/iio/Makefile                     |   1 +
 drivers/iio/industrialio-configfs.c      | 127 +++++++++++++++++++++++++++++++
 include/linux/iio/iio_configfs_trigger.h |  40 ++++++++++
 4 files changed, 176 insertions(+)
 create mode 100644 drivers/iio/industrialio-configfs.c
 create mode 100644 include/linux/iio/iio_configfs_trigger.h

diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
index 4011eff..41d5863 100644
--- a/drivers/iio/Kconfig
+++ b/drivers/iio/Kconfig
@@ -18,6 +18,14 @@ config IIO_BUFFER
 	  Provide core support for various buffer based data
 	  acquisition methods.
 
+config IIO_CONFIGFS
+	tristate "Enable IIO configuration via configfs"
+	select CONFIGFS_FS
+	help
+	  This allows configuring various IIO bits through configfs
+	  (e.g. software triggers). For more info see
+	  Documentation/iio/iio_configfs.txt.
+
 if IIO_BUFFER
 
 config IIO_BUFFER_CB
diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
index 698afc2..90cc407 100644
--- a/drivers/iio/Makefile
+++ b/drivers/iio/Makefile
@@ -5,6 +5,7 @@
 obj-$(CONFIG_IIO) += industrialio.o
 industrialio-y := industrialio-core.o industrialio-event.o inkern.o
 industrialio-$(CONFIG_IIO_BUFFER) += industrialio-buffer.o
+industrialio-$(CONFIG_IIO_CONFIGFS) += industrialio-configfs.o
 industrialio-$(CONFIG_IIO_TRIGGER) += industrialio-trigger.o
 industrialio-$(CONFIG_IIO_BUFFER_CB) += buffer_cb.o
 
diff --git a/drivers/iio/industrialio-configfs.c b/drivers/iio/industrialio-configfs.c
new file mode 100644
index 0000000..d8ffd76
--- /dev/null
+++ b/drivers/iio/industrialio-configfs.c
@@ -0,0 +1,127 @@
+/*
+ * Industrial I/O configfs bits
+ *
+ * Copyright (c) 2015 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/configfs.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kmod.h>
+#include <linux/slab.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/iio_configfs_trigger.h>
+
+static struct iio_configfs_trigger_type *trigger_types[IIO_TRIGGER_TYPE_MAX];
+static DEFINE_RWLOCK(trigger_types_lock);
+
+int register_configfs_trigger(struct iio_configfs_trigger_type *t)
+{
+	int index = t->type;
+	int ret = 0;
+
+	if (index < 0 || index >= IIO_TRIGGER_TYPE_MAX)
+		return -EINVAL;
+
+	write_lock(&trigger_types_lock);
+	if (trigger_types[index])
+		ret = -EBUSY;
+	else
+		trigger_types[index] = t;
+	write_unlock(&trigger_types_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL(register_configfs_trigger);
+
+int unregister_configfs_trigger(struct iio_configfs_trigger_type *t)
+{
+	int index = t->type;
+
+	if (index < 0 || index >= IIO_TRIGGER_TYPE_MAX)
+		return -EINVAL;
+
+	write_lock(&trigger_types_lock);
+	trigger_types[index] = NULL;
+	write_unlock(&trigger_types_lock);
+
+	return 0;
+}
+EXPORT_SYMBOL(unregister_configfs_trigger);
+
+static
+struct iio_configfs_trigger_type *iio_get_configfs_trigger_type(int type)
+{
+	struct iio_configfs_trigger_type *t;
+
+	if (type < 0 || type >= IIO_TRIGGER_TYPE_MAX)
+		return ERR_PTR(-EINVAL);
+
+	read_lock(&trigger_types_lock);
+	t = trigger_types[type];
+	if (t && !try_module_get(t->owner))
+		t = NULL;
+	read_unlock(&trigger_types_lock);
+
+	return t;
+}
+
+static struct config_group *iio_triggers_default_groups[] = {
+	NULL
+};
+
+static struct config_item_type iio_triggers_group_type = {
+	.ct_owner       = THIS_MODULE,
+};
+
+static struct config_group iio_triggers_group = {
+	.cg_item = {
+		.ci_namebuf = "triggers",
+		.ci_type = &iio_triggers_group_type,
+	},
+	.default_groups = iio_triggers_default_groups,
+};
+
+static struct config_group *iio_root_default_groups[] = {
+	&iio_triggers_group,
+	NULL
+};
+
+static struct config_item_type iio_root_group_type = {
+	.ct_owner       = THIS_MODULE,
+};
+
+static struct configfs_subsystem iio_configfs_subsys = {
+	.su_group = {
+		.cg_item = {
+			.ci_namebuf = "iio",
+			.ci_type = &iio_root_group_type,
+		},
+		.default_groups = iio_root_default_groups,
+	},
+	.su_mutex = __MUTEX_INITIALIZER(iio_configfs_subsys.su_mutex),
+};
+
+static int __init iio_configfs_init(void)
+{
+	config_group_init(&iio_triggers_group);
+	config_group_init(&iio_configfs_subsys.su_group);
+
+	return configfs_register_subsystem(&iio_configfs_subsys);
+}
+module_init(iio_configfs_init);
+
+static void __exit iio_configfs_exit(void)
+{
+	configfs_unregister_subsystem(&iio_configfs_subsys);
+}
+module_exit(iio_configfs_exit);
+
+MODULE_AUTHOR("Daniel Baluta <daniel.baluta@intel.com>");
+MODULE_DESCRIPTION("Industrial I/O configfs support");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/iio/iio_configfs_trigger.h b/include/linux/iio/iio_configfs_trigger.h
new file mode 100644
index 0000000..75e76f2
--- /dev/null
+++ b/include/linux/iio/iio_configfs_trigger.h
@@ -0,0 +1,40 @@
+#ifndef __IIO_CONFIGFS_TRIGGER
+#define __IIO_CONFIGFS_TRIGGER
+
+#include <linux/device.h>
+#include <linux/iio/iio.h>
+#include <linux/module.h>
+
+#define module_iio_configfs_trigger_driver(__iio_configfs_trigger) \
+	module_driver(__iio_configfs_trigger, register_configfs_trigger, \
+		      unregister_configfs_trigger)
+
+enum {
+	IIO_TRIGGER_TYPE_MAX,
+};
+
+struct iio_configfs_trigger_ops;
+
+struct iio_configfs_trigger_type {
+	int type;
+	struct module *owner;
+	struct iio_configfs_trigger_ops *trigger_ops;
+};
+
+struct iio_configfs_trigger_info {
+	char *name;
+	struct iio_trigger *trigger;
+	struct iio_configfs_trigger_type *trigger_type;
+};
+
+struct iio_configfs_trigger_ops {
+	int (*get_delay)(struct iio_configfs_trigger_info *, unsigned long *);
+	int (*set_delay)(struct iio_configfs_trigger_info *, unsigned long);
+	int (*probe)(struct iio_configfs_trigger_info *);
+	int (*remove)(struct iio_configfs_trigger_info *);
+};
+
+int register_configfs_trigger(struct iio_configfs_trigger_type *);
+int unregister_configfs_trigger(struct iio_configfs_trigger_type *);
+
+#endif /* __IIO_CONFIGFS_TRIGGER */
-- 
1.9.1