1 files changed, 934 insertions, 0 deletions

diff --git a/drivers/siox/siox-core.c b/drivers/siox/siox-core.c
new file mode 100644
index 000000000..561408583
--- /dev/null
+++ b/drivers/siox/siox-core.c
@@ -0,0 +1,934 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2015-2017 Pengutronix, Uwe Kleine-König <kernel@pengutronix.de>
+ */
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+
+#include "siox.h"
+
+/*
+ * The lowest bit in the SIOX status word signals if the in-device watchdog is
+ * ok. If the bit is set, the device is functional.
+ *
+ * On writing the watchdog timer is reset when this bit toggles.
+ */
+#define SIOX_STATUS_WDG			0x01
+
+/*
+ * Bits 1 to 3 of the status word read as the bitwise negation of what was
+ * clocked in before. The value clocked in is changed in each cycle and so
+ * allows to detect transmit/receive problems.
+ */
+#define SIOX_STATUS_COUNTER		0x0e
+
+/*
+ * Each Siox-Device has a 4 bit type number that is neither 0 nor 15. This is
+ * available in the upper nibble of the read status.
+ *
+ * On write these bits are DC.
+ */
+#define SIOX_STATUS_TYPE		0xf0
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/siox.h>
+
+static bool siox_is_registered;
+
+static void siox_master_lock(struct siox_master *smaster)
+{
+	mutex_lock(&smaster->lock);
+}
+
+static void siox_master_unlock(struct siox_master *smaster)
+{
+	mutex_unlock(&smaster->lock);
+}
+
+static inline u8 siox_status_clean(u8 status_read, u8 status_written)
+{
+	/*
+	 * bits 3:1 of status sample the respective bit in the status
+	 * byte written in the previous cycle but inverted. So if you wrote the
+	 * status word as 0xa before (counter = 0b101), it is expected to get
+	 * back the counter bits as 0b010.
+	 *
+	 * So given the last status written this function toggles the there
+	 * unset counter bits in the read value such that the counter bits in
+	 * the return value are all zero iff the bits were read as expected to
+	 * simplify error detection.
+	 */
+
+	return status_read ^ (~status_written & 0xe);
+}
+
+static bool siox_device_counter_error(struct siox_device *sdevice,
+				      u8 status_clean)
+{
+	return (status_clean & SIOX_STATUS_COUNTER) != 0;
+}
+
+static bool siox_device_type_error(struct siox_device *sdevice, u8 status_clean)
+{
+	u8 statustype = (status_clean & SIOX_STATUS_TYPE) >> 4;
+
+	/*
+	 * If the device knows which value the type bits should have, check
+	 * against this value otherwise just rule out the invalid values 0b0000
+	 * and 0b1111.
+	 */
+	if (sdevice->statustype) {
+		if (statustype != sdevice->statustype)
+			return true;
+	} else {
+		switch (statustype) {
+		case 0:
+		case 0xf:
+			return true;
+		}
+	}
+
+	return false;
+}
+
+static bool siox_device_wdg_error(struct siox_device *sdevice, u8 status_clean)
+{
+	return (status_clean & SIOX_STATUS_WDG) == 0;
+}
+
+/*
+ * If there is a type or counter error the device is called "unsynced".
+ */
+bool siox_device_synced(struct siox_device *sdevice)
+{
+	if (siox_device_type_error(sdevice, sdevice->status_read_clean))
+		return false;
+
+	return !siox_device_counter_error(sdevice, sdevice->status_read_clean);
+
+}
+EXPORT_SYMBOL_GPL(siox_device_synced);
+
+/*
+ * A device is called "connected" if it is synced and the watchdog is not
+ * asserted.
+ */
+bool siox_device_connected(struct siox_device *sdevice)
+{
+	if (!siox_device_synced(sdevice))
+		return false;
+
+	return !siox_device_wdg_error(sdevice, sdevice->status_read_clean);
+}
+EXPORT_SYMBOL_GPL(siox_device_connected);
+
+static void siox_poll(struct siox_master *smaster)
+{
+	struct siox_device *sdevice;
+	size_t i = smaster->setbuf_len;
+	unsigned int devno = 0;
+	int unsync_error = 0;
+
+	smaster->last_poll = jiffies;
+
+	/*
+	 * The counter bits change in each second cycle, the watchdog bit
+	 * toggles each time.
+	 * The counter bits hold values from [0, 6]. 7 would be possible
+	 * theoretically but the protocol designer considered that a bad idea
+	 * for reasons unknown today. (Maybe that's because then the status read
+	 * back has only zeros in the counter bits then which might be confused
+	 * with a stuck-at-0 error. But for the same reason (with s/0/1/) 0
+	 * could be skipped.)
+	 */
+	if (++smaster->status > 0x0d)
+		smaster->status = 0;
+
+	memset(smaster->buf, 0, smaster->setbuf_len);
+
+	/* prepare data pushed out to devices in buf[0..setbuf_len) */
+	list_for_each_entry(sdevice, &smaster->devices, node) {
+		struct siox_driver *sdriver =
+			to_siox_driver(sdevice->dev.driver);
+		sdevice->status_written = smaster->status;
+
+		i -= sdevice->inbytes;
+
+		/*
+		 * If the device or a previous one is unsynced, don't pet the
+		 * watchdog. This is done to ensure that the device is kept in
+		 * reset when something is wrong.
+		 */
+		if (!siox_device_synced(sdevice))
+			unsync_error = 1;
+
+		if (sdriver && !unsync_error)
+			sdriver->set_data(sdevice, sdevice->status_written,
+					  &smaster->buf[i + 1]);
+		else
+			/*
+			 * Don't trigger watchdog if there is no driver or a
+			 * sync problem
+			 */
+			sdevice->status_written &= ~SIOX_STATUS_WDG;
+
+		smaster->buf[i] = sdevice->status_written;
+
+		trace_siox_set_data(smaster, sdevice, devno, i);
+
+		devno++;
+	}
+
+	smaster->pushpull(smaster, smaster->setbuf_len, smaster->buf,
+			  smaster->getbuf_len,
+			  smaster->buf + smaster->setbuf_len);
+
+	unsync_error = 0;
+
+	/* interpret data pulled in from devices in buf[setbuf_len..] */
+	devno = 0;
+	i = smaster->setbuf_len;
+	list_for_each_entry(sdevice, &smaster->devices, node) {
+		struct siox_driver *sdriver =
+			to_siox_driver(sdevice->dev.driver);
+		u8 status = smaster->buf[i + sdevice->outbytes - 1];
+		u8 status_clean;
+		u8 prev_status_clean = sdevice->status_read_clean;
+		bool synced = true;
+		bool connected = true;
+
+		if (!siox_device_synced(sdevice))
+			unsync_error = 1;
+
+		/*
+		 * If the watchdog bit wasn't toggled in this cycle, report the
+		 * watchdog as active to give a consistent view for drivers and
+		 * sysfs consumers.
+		 */
+		if (!sdriver || unsync_error)
+			status &= ~SIOX_STATUS_WDG;
+
+		status_clean =
+			siox_status_clean(status,
+					  sdevice->status_written_lastcycle);
+
+		/* Check counter and type bits */
+		if (siox_device_counter_error(sdevice, status_clean) ||
+		    siox_device_type_error(sdevice, status_clean)) {
+			bool prev_error;
+
+			synced = false;
+
+			/* only report a new error if the last cycle was ok */
+			prev_error =
+				siox_device_counter_error(sdevice,
+							  prev_status_clean) ||
+				siox_device_type_error(sdevice,
+						       prev_status_clean);
+
+			if (!prev_error) {
+				sdevice->status_errors++;
+				sysfs_notify_dirent(sdevice->status_errors_kn);
+			}
+		}
+
+		/* If the device is unsynced report the watchdog as active */
+		if (!synced) {
+			status &= ~SIOX_STATUS_WDG;
+			status_clean &= ~SIOX_STATUS_WDG;
+		}
+
+		if (siox_device_wdg_error(sdevice, status_clean))
+			connected = false;
+
+		/* The watchdog state changed just now */
+		if ((status_clean ^ prev_status_clean) & SIOX_STATUS_WDG) {
+			sysfs_notify_dirent(sdevice->watchdog_kn);
+
+			if (siox_device_wdg_error(sdevice, status_clean)) {
+				struct kernfs_node *wd_errs =
+					sdevice->watchdog_errors_kn;
+
+				sdevice->watchdog_errors++;
+				sysfs_notify_dirent(wd_errs);
+			}
+		}
+
+		if (connected != sdevice->connected)
+			sysfs_notify_dirent(sdevice->connected_kn);
+
+		sdevice->status_read_clean = status_clean;
+		sdevice->status_written_lastcycle = sdevice->status_written;
+		sdevice->connected = connected;
+
+		trace_siox_get_data(smaster, sdevice, devno, status_clean, i);
+
+		/* only give data read to driver if the device is connected */
+		if (sdriver && connected)
+			sdriver->get_data(sdevice, &smaster->buf[i]);
+
+		devno++;
+		i += sdevice->outbytes;
+	}
+}
+
+static int siox_poll_thread(void *data)
+{
+	struct siox_master *smaster = data;
+	signed long timeout = 0;
+
+	get_device(&smaster->dev);
+
+	for (;;) {
+		if (kthread_should_stop()) {
+			put_device(&smaster->dev);
+			return 0;
+		}
+
+		siox_master_lock(smaster);
+
+		if (smaster->active) {
+			unsigned long next_poll =
+				smaster->last_poll + smaster->poll_interval;
+			if (time_is_before_eq_jiffies(next_poll))
+				siox_poll(smaster);
+
+			timeout = smaster->poll_interval -
+				(jiffies - smaster->last_poll);
+		} else {
+			timeout = MAX_SCHEDULE_TIMEOUT;
+		}
+
+		/*
+		 * Set the task to idle while holding the lock. This makes sure
+		 * that we don't sleep too long when the bus is reenabled before
+		 * schedule_timeout is reached.
+		 */
+		if (timeout > 0)
+			set_current_state(TASK_IDLE);
+
+		siox_master_unlock(smaster);
+
+		if (timeout > 0)
+			schedule_timeout(timeout);
+
+		/*
+		 * I'm not clear if/why it is important to set the state to
+		 * RUNNING again, but it fixes a "do not call blocking ops when
+		 * !TASK_RUNNING;"-warning.
+		 */
+		set_current_state(TASK_RUNNING);
+	}
+}
+
+static int __siox_start(struct siox_master *smaster)
+{
+	if (!(smaster->setbuf_len + smaster->getbuf_len))
+		return -ENODEV;
+
+	if (!smaster->buf)
+		return -ENOMEM;
+
+	if (smaster->active)
+		return 0;
+
+	smaster->active = 1;
+	wake_up_process(smaster->poll_thread);
+
+	return 1;
+}
+
+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)
+{
+	if (smaster->active) {
+		struct siox_device *sdevice;
+
+		smaster->active = 0;
+
+		list_for_each_entry(sdevice, &smaster->devices, node) {
+			if (sdevice->connected)
+				sysfs_notify_dirent(sdevice->connected_kn);
+			sdevice->connected = false;
+		}
+
+		return 1;
+	}
+	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 int 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 connected_show(struct device *dev,
+			      struct device_attribute *attr, char *buf)
+{
+	struct siox_device *sdev = to_siox_device(dev);
+	bool connected;
+
+	siox_master_lock(sdev->smaster);
+
+	connected = sdev->connected;
+
+	siox_master_unlock(sdev->smaster);
+
+	return sprintf(buf, "%u\n", connected);
+}
+
+static DEVICE_ATTR_RO(connected);
+
+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_read_clean;
+
+	siox_master_unlock(sdev->smaster);
+
+	return sprintf(buf, "%d\n", status & SIOX_STATUS_WDG);
+}
+
+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_connected.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 int siox_probe(struct device *dev)
+{
+	struct siox_driver *sdriver = to_siox_driver(dev->driver);
+	struct siox_device *sdevice = to_siox_device(dev);
+
+	return sdriver->probe(sdevice);
+}
+
+static void siox_remove(struct device *dev)
+{
+	struct siox_driver *sdriver =
+		container_of(dev->driver, struct siox_driver, driver);
+	struct siox_device *sdevice = to_siox_device(dev);
+
+	if (sdriver->remove)
+		sdriver->remove(sdevice);
+}
+
+static void siox_shutdown(struct device *dev)
+{
+	struct siox_device *sdevice = to_siox_device(dev);
+	struct siox_driver *sdriver;
+
+	if (!dev->driver)
+		return;
+
+	sdriver = container_of(dev->driver, struct siox_driver, driver);
+	if (sdriver->shutdown)
+		sdriver->shutdown(sdevice);
+}
+
+static struct bus_type siox_bus_type = {
+	.name = "siox",
+	.match = siox_match,
+	.probe = siox_probe,
+	.remove = siox_remove,
+	.shutdown = siox_shutdown,
+};
+
+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)
+		ret = siox_start(smaster);
+	else
+		ret = siox_stop(smaster);
+
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(active);
+
+static struct siox_device *siox_device_add(struct siox_master *smaster,
+					   const char *type, size_t inbytes,
+					   size_t outbytes, u8 statustype);
+
+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;
+	u8 statustype = 0;
+
+	ret = sscanf(buf, "%19s %zu %zu %hhu", type, &inbytes,
+		     &outbytes, &statustype);
+	if (ret != 3 && ret != 4)
+		return -EINVAL;
+
+	if (strcmp(type, "siox-12x8") || inbytes != 2 || outbytes != 4)
+		return -EINVAL;
+
+	siox_device_add(smaster, "siox-12x8", inbytes, outbytes, statustype);
+
+	return count;
+}
+
+static DEVICE_ATTR_WO(device_add);
+
+static void siox_device_remove(struct siox_master *smaster);
+
+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;
+
+	ret = kstrtou64(buf, 0, &val);
+	if (ret < 0)
+		return ret;
+
+	siox_master_lock(smaster);
+
+	smaster->poll_interval = nsecs_to_jiffies(val);
+
+	siox_master_unlock(smaster);
+
+	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)
+{
+	int ret;
+
+	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);
+
+	smaster->last_poll = jiffies;
+	smaster->poll_thread = kthread_run(siox_poll_thread, smaster,
+					   "siox-%d", smaster->busno);
+	if (IS_ERR(smaster->poll_thread)) {
+		smaster->active = 0;
+		return PTR_ERR(smaster->poll_thread);
+	}
+
+	ret = device_add(&smaster->dev);
+	if (ret)
+		kthread_stop(smaster->poll_thread);
+
+	return ret;
+}
+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);
+
+static struct siox_device *siox_device_add(struct siox_master *smaster,
+					   const char *type, size_t inbytes,
+					   size_t outbytes, u8 statustype)
+{
+	struct siox_device *sdevice;
+	int ret;
+	size_t buf_len;
+
+	sdevice = kzalloc(sizeof(*sdevice), GFP_KERNEL);
+	if (!sdevice)
+		return ERR_PTR(-ENOMEM);
+
+	sdevice->type = type;
+	sdevice->inbytes = inbytes;
+	sdevice->outbytes = outbytes;
+	sdevice->statustype = statustype;
+
+	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);
+
+	buf_len = smaster->setbuf_len + inbytes +
+		smaster->getbuf_len + outbytes;
+	if (smaster->buf_len < buf_len) {
+		u8 *buf = krealloc(smaster->buf, buf_len, GFP_KERNEL);
+
+		if (!buf) {
+			dev_err(&smaster->dev,
+				"failed to realloc buffer to %zu\n", buf_len);
+			ret = -ENOMEM;
+			goto err_buf_alloc;
+		}
+
+		smaster->buf_len = buf_len;
+		smaster->buf = buf;
+	}
+
+	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;
+
+	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");
+	sdevice->connected_kn = sysfs_get_dirent(sdevice->dev.kobj.sd,
+						 "connected");
+
+	siox_master_unlock(smaster);
+
+	return sdevice;
+
+err_device_register:
+	/* don't care to make the buffer smaller again */
+	put_device(&sdevice->dev);
+	sdevice = NULL;
+
+err_buf_alloc:
+	siox_master_unlock(smaster);
+
+	kfree(sdevice);
+
+	return ERR_PTR(ret);
+}
+
+static void siox_device_remove(struct siox_master *smaster)
+{
+	struct siox_device *sdevice;
+
+	siox_master_lock(smaster);
+
+	if (!smaster->num_devices) {
+		siox_master_unlock(smaster);
+		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->probe ||
+	    (!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;
+
+	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;
+	}
+
+	siox_is_registered = true;
+
+	return 0;
+}
+subsys_initcall(siox_init);
+
+static void __exit siox_exit(void)
+{
+	bus_unregister(&siox_bus_type);
+}
+module_exit(siox_exit);
+
+MODULE_AUTHOR("Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de>");
+MODULE_DESCRIPTION("Eckelmann SIOX driver core");
+MODULE_LICENSE("GPL v2");