[PATCH RFC v3 1/4] siox: new driver framework for eckelmann SIOX

[Uwe Kleine-KÃnig]

SIOX is a synchronous serial protocol that uses four logical lines. Each
bus has a single master device that controls DCLK, DOUT and DLD lines.
The bus clients drive DIN to the master using a daisy chain that is
clocked by DCLK.

The topology looks as follows:

      ,------->--DCLK-->---------------+----------------------
      ^                                v                      v
 ,--------.                ,----------------------.       ,--------
 |        |                |   ,--------------.   |       |
 |        |--->--DOUT-->---|->-|shift register|->-|--->---|
 |        |                |   `--------------'   |       |
 | master |                |        device        |       |  device
 |        |                |   ,--------------.   |       |
 |        |---<--DIN---<---|-<-|shift register|-<-|---<---|
 |        |                |   `--------------'   |       |
 `--------'                `----------------------'       `--------
      v                                ^                      ^
      `----------DLD-------------------+----------------------'

A pulse on DLD makes the devices sample their input and output stated from/to
DIN and DOUT. A pulse on DCLK shifts both chains by a single bit.

The framework added with this patch formalizes a SIOX master.

Signed-off-by: Uwe Kleine-KÃnig <u.kleine-koenig@xxxxxxxxxxxxxx>
---
 drivers/Kconfig          |   2 +
 drivers/Makefile         |   1 +
 drivers/siox/Kconfig     |   2 +
 drivers/siox/Makefile    |   1 +
 drivers/siox/siox-core.c | 674 +++++++++++++++++++++++++++++++++++++++++++++++
 drivers/siox/siox.h      |  52 ++++
 include/linux/siox.h     |  61 +++++
 7 files changed, 793 insertions(+)
 create mode 100644 drivers/siox/Kconfig
 create mode 100644 drivers/siox/Makefile
 create mode 100644 drivers/siox/siox-core.c
 create mode 100644 drivers/siox/siox.h
 create mode 100644 include/linux/siox.h

diff --git a/drivers/Kconfig b/drivers/Kconfig
index d2ac339de85f..2b8911b05ff5 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -198,4 +198,6 @@ source "drivers/hwtracing/intel_th/Kconfig"
 
 source "drivers/fpga/Kconfig"
 
+source "drivers/siox/Kconfig"
+
 endmenu
diff --git a/drivers/Makefile b/drivers/Makefile
index 8f5d076baeb0..9ef4af303839 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -172,3 +172,4 @@ obj-$(CONFIG_STM)		+= hwtracing/stm/
 obj-$(CONFIG_ANDROID)		+= android/
 obj-$(CONFIG_NVMEM)		+= nvmem/
 obj-$(CONFIG_FPGA)		+= fpga/
+obj-$(CONFIG_SIOX)		+= siox/
diff --git a/drivers/siox/Kconfig b/drivers/siox/Kconfig
new file mode 100644
index 000000000000..471fbc009521
--- /dev/null
+++ b/drivers/siox/Kconfig
@@ -0,0 +1,2 @@
+menuconfig SIOX
+	tristate "Eckelmann SIOX Support"
diff --git a/drivers/siox/Makefile b/drivers/siox/Makefile
new file mode 100644
index 000000000000..d55cb5e08868
--- /dev/null
+++ b/drivers/siox/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_SIOX) += siox-core.o
diff --git a/drivers/siox/siox-core.c b/drivers/siox/siox-core.c
new file mode 100644
index 000000000000..b4a128218d7d
--- /dev/null
+++ b/drivers/siox/siox-core.c
@@ -0,0 +1,674 @@
+/*
+ * Copyright (C) 2015 Pengutronix, Uwe Kleine-KÃnig <kernel@xxxxxxxxxxxxxx>
+ *
+ * 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/kernel.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+
+#include "siox.h"
+
+struct workqueue_struct *wqueue;
+static bool siox_is_registered;
+
+void siox_master_lock(struct siox_master *smaster)
+{
+	mutex_lock(&smaster->lock);
+}
+
+void siox_master_unlock(struct siox_master *smaster)
+{
+	mutex_unlock(&smaster->lock);
+}
+
+struct siox_device *siox_device_add(struct siox_master *smaster);
+void siox_device_remove(struct siox_master *smaster);
+
+static void __siox_poll(struct siox_master *smaster)
+{
+	struct siox_device *sdevice;
+	size_t i = 0;
+	u8 prevstatus = smaster->status;
+
+	if (++smaster->status > 0x0d)
+		smaster->status = 0;
+
+	memset(smaster->buf, 0, smaster->setbuf_len);
+
+	list_for_each_entry_reverse(sdevice, &smaster->devices, node) {
+		struct siox_driver *sdriver =
+			sdevice->dev.driver ? to_siox_driver(sdevice->dev.driver) : NULL;
+
+		if (sdriver)
+			sdriver->set_data(sdevice, smaster->status,
+					  &smaster->buf[i + 1]);
+
+		smaster->buf[i] = smaster->status;
+
+		i += sdevice->inbytes;
+	}
+
+	BUG_ON(i != smaster->setbuf_len);
+
+	smaster->pushpull(smaster, smaster->setbuf_len, smaster->buf,
+			  smaster->getbuf_len,
+			  smaster->buf + smaster->setbuf_len);
+
+	list_for_each_entry(sdevice, &smaster->devices, node) {
+		struct siox_driver *sdriver =
+			sdevice->dev.driver ? to_siox_driver(sdevice->dev.driver) : NULL;
+		u8 sdev_status = smaster->buf[i + sdevice->outbytes - 1];
+
+		/*
+		 * bits 4:2 of status sample the respective bit in the status
+		 * byte written in the previous cycle. Mask them out
+		 * accordingly such that a set bit there indicates an error.
+		 */
+		sdev_status ^= ~prevstatus & 0xe;
+
+		if ((sdevice->status ^ sdev_status) & 1)
+			sysfs_notify_dirent(sdevice->watchdog_kn);
+
+		if (!(sdev_status & 1)) {
+			sdevice->watchdog_errors++;
+			sysfs_notify_dirent(sdevice->watchdog_errors_kn);
+		}
+
+		if (sdev_status & 0xe) {
+			sdevice->status_errors++;
+			sysfs_notify_dirent(sdevice->status_errors_kn);
+		}
+
+		sdevice->status = sdev_status;
+
+		/*
+		 * XXX trigger events for watchdog, changed jumper and misread
+		 * counter. Should the bus stop to poll in these cases?
+		 */
+
+		if (sdriver)
+			sdriver->get_data(sdevice, &smaster->buf[i]);
+
+		i += sdevice->outbytes;
+	}
+
+	if (smaster->active)
+		queue_delayed_work(wqueue, &smaster->poll,
+				   smaster->poll_interval);
+}
+
+static void siox_poll(struct work_struct *work)
+{
+	struct delayed_work *dwork = to_delayed_work(work);
+	struct siox_master *smaster =
+		container_of(dwork, struct siox_master, poll);
+
+	get_device(&smaster->dev);
+	siox_master_lock(smaster);
+	if (likely(smaster->active))
+		__siox_poll(smaster);
+	siox_master_unlock(smaster);
+	put_device(&smaster->dev);
+}
+
+static int __siox_start(struct siox_master *smaster)
+{
+	if (!(smaster->setbuf_len + smaster->getbuf_len))
+		return -ENODEV;
+
+	if (!smaster->buf)
+		return -ENOMEM;
+
+	smaster->active = 1;
+
+	__siox_poll(smaster);
+
+	return 0;
+}
+
+static int siox_start(struct siox_master *smaster)
+{
+	int ret;
+
+	siox_master_lock(smaster);
+	ret = __siox_start(smaster);
+	siox_master_unlock(smaster);
+
+	return ret;
+}
+
+static int __siox_stop(struct siox_master *smaster)
+{
+	smaster->active = 0;
+	cancel_delayed_work(&smaster->poll);
+	return 0;
+}
+
+static int siox_stop(struct siox_master *smaster)
+{
+	int ret;
+
+	siox_master_lock(smaster);
+	ret = __siox_stop(smaster);
+	siox_master_unlock(smaster);
+
+	return ret;
+}
+
+static ssize_t type_show(struct device *dev,
+			 struct device_attribute *attr, char *buf)
+{
+	struct siox_device *sdev = to_siox_device(dev);
+
+	return sprintf(buf, "%s\n", sdev->type);
+}
+
+static DEVICE_ATTR_RO(type);
+
+static ssize_t inbytes_show(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	struct siox_device *sdev = to_siox_device(dev);
+
+	return sprintf(buf, "%zu\n", sdev->inbytes);
+}
+
+static DEVICE_ATTR_RO(inbytes);
+
+static ssize_t outbytes_show(struct device *dev,
+			     struct device_attribute *attr, char *buf)
+{
+	struct siox_device *sdev = to_siox_device(dev);
+
+	return sprintf(buf, "%zu\n", sdev->outbytes);
+}
+
+static DEVICE_ATTR_RO(outbytes);
+
+static ssize_t status_errors_show(struct device *dev,
+				  struct device_attribute *attr, char *buf)
+{
+	struct siox_device *sdev = to_siox_device(dev);
+	unsigned status_errors;
+
+	siox_master_lock(sdev->smaster);
+
+	status_errors = sdev->status_errors;
+
+	siox_master_unlock(sdev->smaster);
+
+	return sprintf(buf, "%u\n", status_errors);
+}
+
+static DEVICE_ATTR_RO(status_errors);
+
+static ssize_t watchdog_show(struct device *dev,
+			     struct device_attribute *attr, char *buf)
+{
+	struct siox_device *sdev = to_siox_device(dev);
+	u8 status;
+
+	siox_master_lock(sdev->smaster);
+
+	status = sdev->status;
+
+	siox_master_unlock(sdev->smaster);
+
+	return sprintf(buf, "%d\n", status & 1);
+}
+
+static DEVICE_ATTR_RO(watchdog);
+
+static ssize_t watchdog_errors_show(struct device *dev,
+				    struct device_attribute *attr, char *buf)
+{
+	struct siox_device *sdev = to_siox_device(dev);
+	unsigned int watchdog_errors;
+
+	siox_master_lock(sdev->smaster);
+
+	watchdog_errors = sdev->watchdog_errors;
+
+	siox_master_unlock(sdev->smaster);
+
+	return sprintf(buf, "%u\n", watchdog_errors);
+}
+
+static DEVICE_ATTR_RO(watchdog_errors);
+
+static struct attribute *siox_device_attrs[] = {
+	&dev_attr_type.attr,
+	&dev_attr_inbytes.attr,
+	&dev_attr_outbytes.attr,
+	&dev_attr_status_errors.attr,
+	&dev_attr_watchdog.attr,
+	&dev_attr_watchdog_errors.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(siox_device);
+
+static void siox_device_release(struct device *dev)
+{
+	struct siox_device *sdevice = to_siox_device(dev);
+
+	kfree(sdevice);
+}
+
+static struct device_type siox_device_type = {
+	.groups = siox_device_groups,
+	.release = siox_device_release,
+};
+
+static int siox_match(struct device *dev, struct device_driver *drv)
+{
+	if (dev->type != &siox_device_type)
+		return 0;
+
+	/* up to now there is only a single driver so keeping this simple */
+	return 1;
+}
+
+static struct bus_type siox_bus_type = {
+	.name = "siox",
+	.match = siox_match,
+};
+
+static int siox_driver_probe(struct device *dev)
+{
+	struct siox_driver *sdriver = to_siox_driver(dev->driver);
+	struct siox_device *sdevice = to_siox_device(dev);
+	int ret;
+
+	ret = sdriver->probe(sdevice);
+	return ret;
+}
+
+static int siox_driver_remove(struct device *dev)
+{
+	struct siox_driver *sdriver =
+		container_of(dev->driver, struct siox_driver, driver);
+	struct siox_device *sdevice = to_siox_device(dev);
+	int ret;
+
+	ret = sdriver->remove(sdevice);
+	return ret;
+}
+
+static void siox_driver_shutdown(struct device *dev)
+{
+	struct siox_driver *sdriver =
+		container_of(dev->driver, struct siox_driver, driver);
+	struct siox_device *sdevice = to_siox_device(dev);
+
+	sdriver->shutdown(sdevice);
+}
+
+static ssize_t active_show(struct device *dev,
+			   struct device_attribute *attr, char *buf)
+{
+	struct siox_master *smaster = to_siox_master(dev);
+
+	return sprintf(buf, "%d\n", smaster->active);
+}
+
+static ssize_t active_store(struct device *dev,
+			    struct device_attribute *attr,
+			    const char *buf, size_t count)
+{
+	struct siox_master *smaster = to_siox_master(dev);
+	int ret;
+	int active;
+
+	ret = kstrtoint(buf, 0, &active);
+	if (ret < 0)
+		return ret;
+
+	if (!active == !smaster->active)
+		/* no change */
+		return count;
+
+	if (active)
+		ret = siox_start(smaster);
+	else
+		ret = siox_stop(smaster);
+
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(active);
+
+static ssize_t device_add_store(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t count)
+{
+	struct siox_master *smaster = to_siox_master(dev);
+	int ret;
+	char type[20] = "";
+	size_t inbytes = 0, outbytes = 0;
+
+	ret = sscanf(buf, "%20s %zu %zu", type, &inbytes, &outbytes);
+	if (ret != 3 || strcmp(type, "siox-12x8") ||
+	    inbytes != 2 || outbytes != 4)
+		return -EINVAL;
+
+	siox_device_add(smaster);
+
+	return count;
+}
+
+static DEVICE_ATTR_WO(device_add);
+
+static ssize_t device_remove_store(struct device *dev,
+				   struct device_attribute *attr,
+				   const char *buf, size_t count)
+{
+	struct siox_master *smaster = to_siox_master(dev);
+
+	/* XXX? require to write <type> <inbytes> <outbytes> */
+	siox_device_remove(smaster);
+
+	return count;
+}
+
+static DEVICE_ATTR_WO(device_remove);
+
+static ssize_t poll_interval_ns_show(struct device *dev,
+				     struct device_attribute *attr, char *buf)
+{
+	struct siox_master *smaster = to_siox_master(dev);
+
+	return sprintf(buf, "%lld\n", jiffies_to_nsecs(smaster->poll_interval));
+}
+
+static ssize_t poll_interval_ns_store(struct device *dev,
+				      struct device_attribute *attr,
+				      const char *buf, size_t count)
+{
+	struct siox_master *smaster = to_siox_master(dev);
+	int ret;
+	u64 val;
+
+	siox_master_lock(smaster);
+
+	ret = kstrtou64(buf, 0, &val);
+	if (ret)
+		goto out_unlock;
+
+	smaster->poll_interval = nsecs_to_jiffies(val);
+
+out_unlock:
+	siox_master_unlock(smaster);
+
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(poll_interval_ns);
+
+static struct attribute *siox_master_attrs[] = {
+	&dev_attr_active.attr,
+	&dev_attr_device_add.attr,
+	&dev_attr_device_remove.attr,
+	&dev_attr_poll_interval_ns.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(siox_master);
+
+static void siox_master_release(struct device *dev)
+{
+	struct siox_master *smaster = to_siox_master(dev);
+
+	kfree(smaster);
+}
+
+static struct device_type siox_master_type = {
+	.groups = siox_master_groups,
+	.release = siox_master_release,
+};
+
+struct siox_master *siox_master_alloc(struct device *dev,
+				      size_t size)
+{
+	struct siox_master *smaster;
+
+	if (!dev)
+		return NULL;
+
+	smaster = kzalloc(sizeof(*smaster) + size, GFP_KERNEL);
+	if (!smaster)
+		return NULL;
+
+	device_initialize(&smaster->dev);
+
+	smaster->busno = -1;
+	smaster->dev.bus = &siox_bus_type;
+	smaster->dev.type = &siox_master_type;
+	smaster->dev.parent = dev;
+	smaster->poll_interval = DIV_ROUND_UP(HZ, 40);
+
+	dev_set_drvdata(&smaster->dev, &smaster[1]);
+
+	return smaster;
+}
+EXPORT_SYMBOL_GPL(siox_master_alloc);
+
+int siox_master_register(struct siox_master *smaster)
+{
+	if (!siox_is_registered)
+		return -EPROBE_DEFER;
+
+	if (!smaster->pushpull)
+		return -EINVAL;
+
+	dev_set_name(&smaster->dev, "siox-%d", smaster->busno);
+
+	mutex_init(&smaster->lock);
+	INIT_LIST_HEAD(&smaster->devices);
+	INIT_DELAYED_WORK(&smaster->poll, siox_poll);
+
+	return device_add(&smaster->dev);
+}
+EXPORT_SYMBOL_GPL(siox_master_register);
+
+void siox_master_unregister(struct siox_master *smaster)
+{
+	/* remove device */
+	device_del(&smaster->dev);
+
+	siox_master_lock(smaster);
+
+	__siox_stop(smaster);
+
+	while (smaster->num_devices) {
+		struct siox_device *sdevice;
+
+		sdevice = container_of(smaster->devices.prev, struct siox_device, node);
+		list_del(&sdevice->node);
+		smaster->num_devices--;
+
+		siox_master_unlock(smaster);
+
+		device_unregister(&sdevice->dev);
+
+		siox_master_lock(smaster);
+	}
+
+	siox_master_unlock(smaster);
+
+	put_device(&smaster->dev);
+}
+EXPORT_SYMBOL_GPL(siox_master_unregister);
+
+struct siox_device *siox_device_add(struct siox_master *smaster)
+{
+	struct siox_device *sdevice;
+	int ret;
+
+	sdevice = kzalloc(sizeof(*sdevice), GFP_KERNEL);
+	if (!sdevice)
+		return NULL;
+
+	sdevice->type = "siox-12x8";
+	sdevice->inbytes = 2;
+	sdevice->outbytes = 4;
+
+	sdevice->smaster = smaster;
+	sdevice->dev.parent = &smaster->dev;
+	sdevice->dev.bus = &siox_bus_type;
+	sdevice->dev.type = &siox_device_type;
+
+	siox_master_lock(smaster);
+
+	dev_set_name(&sdevice->dev, "siox-%d-%d",
+		     smaster->busno, smaster->num_devices);
+
+	ret = device_register(&sdevice->dev);
+	if (ret) {
+		dev_err(&smaster->dev, "failed to register device: %d\n", ret);
+
+		goto err_device_register;
+	}
+
+	smaster->num_devices++;
+	list_add_tail(&sdevice->node, &smaster->devices);
+
+	smaster->setbuf_len += sdevice->inbytes;
+	smaster->getbuf_len += sdevice->outbytes;
+
+	if (smaster->buf_len < smaster->setbuf_len + smaster->getbuf_len) {
+		smaster->buf_len = smaster->setbuf_len + smaster->getbuf_len;
+		smaster->buf = krealloc(smaster->buf,
+					smaster->buf_len, GFP_KERNEL);
+		if (!smaster->buf) {
+			dev_err(&smaster->dev,
+				"failed to realloc buffer to %zu\n",
+				smaster->buf_len);
+			if (smaster->active)
+				__siox_stop(smaster);
+		}
+	}
+
+	siox_master_unlock(smaster);
+
+	sdevice->status_errors_kn = sysfs_get_dirent(sdevice->dev.kobj.sd,
+						     "status_errors");
+	sdevice->watchdog_kn = sysfs_get_dirent(sdevice->dev.kobj.sd,
+						"watchdog");
+	sdevice->watchdog_errors_kn = sysfs_get_dirent(sdevice->dev.kobj.sd,
+						       "watchdog_errors");
+
+	return sdevice;
+
+err_device_register:
+	siox_master_unlock(smaster);
+
+	kfree(sdevice);
+
+	return ERR_PTR(ret);
+}
+
+void siox_device_remove(struct siox_master *smaster)
+{
+	struct siox_device *sdevice;
+
+	siox_master_lock(smaster);
+
+	if (!smaster->num_devices)
+		return;
+
+	sdevice = container_of(smaster->devices.prev, struct siox_device, node);
+	list_del(&sdevice->node);
+	smaster->num_devices--;
+
+	smaster->setbuf_len -= sdevice->inbytes;
+	smaster->getbuf_len -= sdevice->outbytes;
+
+	if (!smaster->num_devices)
+		__siox_stop(smaster);
+
+	siox_master_unlock(smaster);
+
+	/*
+	 * This must be done without holding the master lock because we're
+	 * called from device_remove_store which also holds a sysfs mutex.
+	 * device_unregister tries to aquire the same lock.
+	 */
+	device_unregister(&sdevice->dev);
+}
+
+int __siox_driver_register(struct siox_driver *sdriver, struct module *owner)
+{
+	int ret;
+
+	if (unlikely(!siox_is_registered))
+		return -EPROBE_DEFER;
+
+	if (!sdriver->set_data && !sdriver->get_data) {
+		pr_err("Driver %s doesn't provide needed callbacks\n",
+		       sdriver->driver.name);
+		return -EINVAL;
+	}
+
+	sdriver->driver.owner = owner;
+	sdriver->driver.bus = &siox_bus_type;
+
+	if (sdriver->probe)
+		sdriver->driver.probe = siox_driver_probe;
+	if (sdriver->remove)
+		sdriver->driver.remove = siox_driver_remove;
+	if (sdriver->shutdown)
+		sdriver->driver.shutdown = siox_driver_shutdown;
+
+	ret = driver_register(&sdriver->driver);
+	if (ret)
+		pr_err("Failed to register siox driver %s (%d)\n",
+		       sdriver->driver.name, ret);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(__siox_driver_register);
+
+static int __init siox_init(void)
+{
+	int ret;
+
+	ret = bus_register(&siox_bus_type);
+	if (ret) {
+		pr_err("Registration of SIOX bus type failed: %d\n", ret);
+		return ret;
+	}
+
+	wqueue = create_singlethread_workqueue("siox");
+	if (!wqueue) {
+		pr_err("Creation of siox workqueue failed\n");
+		bus_unregister(&siox_bus_type);
+		return -ENOMEM;
+	}
+
+	siox_is_registered = true;
+
+	return 0;
+}
+subsys_initcall(siox_init);
+
+static void __exit siox_exit(void)
+{
+	flush_workqueue(wqueue);
+	destroy_workqueue(wqueue);
+	bus_unregister(&siox_bus_type);
+}
+module_exit(siox_exit);
+
+MODULE_AUTHOR("Uwe Kleine-Koenig <u.kleine-koenig@xxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Eckelmann SIOX driver core");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/siox/siox.h b/drivers/siox/siox.h
new file mode 100644
index 000000000000..1c51ccc7628f
--- /dev/null
+++ b/drivers/siox/siox.h
@@ -0,0 +1,52 @@
+/*
+ * Copyright (C) 2015 Pengutronix, Uwe Kleine-KÃnig <kernel@xxxxxxxxxxxxxx>
+ *
+ * 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/kernel.h>
+#include <linux/workqueue.h>
+
+#include <linux/siox.h>
+
+#define to_siox_master(_dev)	container_of((_dev), struct siox_master, dev)
+struct siox_master {
+	/* these fields should be initialized by the driver */
+	int busno;
+	int (*pushpull)(struct siox_master *smaster,
+			size_t setbuf_len, const u8 setbuf[],
+			size_t getbuf_len, u8 getbuf[]);
+
+	/* might be initialized by the driver, if 0 it is set to HZ / 40 */
+	unsigned long poll_interval; /* in jiffies */
+
+	/* framework private stuff */
+	struct mutex lock;
+	bool active;
+	struct module *owner;
+	struct device dev;
+	unsigned num_devices;
+	struct list_head devices;
+
+	size_t setbuf_len, getbuf_len;
+	size_t buf_len;
+	u8 *buf;
+	u8 status;
+
+	struct delayed_work poll;
+};
+
+static inline void *siox_master_get_devdata(struct siox_master *smaster)
+{
+	return dev_get_drvdata(&smaster->dev);
+}
+
+struct siox_master *siox_master_alloc(struct device *dev, size_t size);
+static inline void siox_master_put(struct siox_master *smaster)
+{
+	put_device(&smaster->dev);
+}
+
+int siox_master_register(struct siox_master *smaster);
+void siox_master_unregister(struct siox_master *smaster);
diff --git a/include/linux/siox.h b/include/linux/siox.h
new file mode 100644
index 000000000000..0bd57dcc6f6b
--- /dev/null
+++ b/include/linux/siox.h
@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2015 Pengutronix, Uwe Kleine-KÃnig <kernel@xxxxxxxxxxxxxx>
+ *
+ * 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/device.h>
+
+#define to_siox_device(_dev)	container_of((_dev), struct siox_device, dev)
+struct siox_device {
+	struct list_head node; /* node in smaster->devices */
+	struct siox_master *smaster;
+	struct device dev;
+
+	char *type;
+	size_t inbytes;
+	size_t outbytes;
+
+	u8 status;
+
+	/* statistics */
+	unsigned int watchdog_errors;
+	unsigned int status_errors;
+
+	struct kernfs_node *status_errors_kn;
+	struct kernfs_node *watchdog_kn;
+	struct kernfs_node *watchdog_errors_kn;
+};
+
+#define to_siox_driver(_drv)	container_of((_drv), struct siox_driver, driver)
+struct siox_driver {
+	int (*probe)(struct siox_device *);
+	int (*remove)(struct siox_device *);
+	void (*shutdown)(struct siox_device *);
+
+	/*
+	 * buf is big enough to hold sdev->inbytes - 1 bytes, the status byte
+	 * is in the scope of the framework.
+	 */
+	int (*set_data)(struct siox_device *, u8 status, u8 buf[]);
+	/*
+	 * buf is big enough to hold sdev->outbytes - 1 bytes, the status byte
+	 * is in the scope of the framework
+	 */
+	int (*get_data)(struct siox_device *, const u8 buf[]);
+
+	struct device_driver driver;
+};
+
+int __siox_driver_register(struct siox_driver *sdriver, struct module *owner);
+static inline int siox_driver_register(struct siox_driver *sdriver)
+{
+	return __siox_driver_register(sdriver, THIS_MODULE);
+}
+
+static inline void siox_driver_unregister(struct siox_driver *sdriver)
+{
+	return driver_unregister(&sdriver->driver);
+}
-- 
2.8.0.rc3