Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

1 files changed, 806 insertions, 0 deletions

diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c
new file mode 100644
index 000000000..ccaac5e29
--- /dev/null
+++ b/drivers/i2c/i2c-dev.c
@@ -0,0 +1,806 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+    i2c-dev.c - i2c-bus driver, char device interface
+
+    Copyright (C) 1995-97 Simon G. Vogl
+    Copyright (C) 1998-99 Frodo Looijaard <frodol@dds.nl>
+    Copyright (C) 2003 Greg Kroah-Hartman <greg@kroah.com>
+
+*/
+
+/* Note that this is a complete rewrite of Simon Vogl's i2c-dev module.
+   But I have used so much of his original code and ideas that it seems
+   only fair to recognize him as co-author -- Frodo */
+
+/* The I2C_RDWR ioctl code is written by Kolja Waschk <waschk@telos.de> */
+
+#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
+
+#include <linux/cdev.h>
+#include <linux/compat.h>
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/i2c-dev.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/jiffies.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/notifier.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+
+/*
+ * An i2c_dev represents an i2c_adapter ... an I2C or SMBus master, not a
+ * slave (i2c_client) with which messages will be exchanged.  It's coupled
+ * with a character special file which is accessed by user mode drivers.
+ *
+ * The list of i2c_dev structures is parallel to the i2c_adapter lists
+ * maintained by the driver model, and is updated using bus notifications.
+ */
+struct i2c_dev {
+	struct list_head list;
+	struct i2c_adapter *adap;
+	struct device dev;
+	struct cdev cdev;
+};
+
+#define I2C_MINORS	(MINORMASK + 1)
+static LIST_HEAD(i2c_dev_list);
+static DEFINE_SPINLOCK(i2c_dev_list_lock);
+
+static struct i2c_dev *i2c_dev_get_by_minor(unsigned index)
+{
+	struct i2c_dev *i2c_dev;
+
+	spin_lock(&i2c_dev_list_lock);
+	list_for_each_entry(i2c_dev, &i2c_dev_list, list) {
+		if (i2c_dev->adap->nr == index)
+			goto found;
+	}
+	i2c_dev = NULL;
+found:
+	spin_unlock(&i2c_dev_list_lock);
+	return i2c_dev;
+}
+
+static struct i2c_dev *get_free_i2c_dev(struct i2c_adapter *adap)
+{
+	struct i2c_dev *i2c_dev;
+
+	if (adap->nr >= I2C_MINORS) {
+		pr_err("Out of device minors (%d)\n", adap->nr);
+		return ERR_PTR(-ENODEV);
+	}
+
+	i2c_dev = kzalloc_obj(*i2c_dev);
+	if (!i2c_dev)
+		return ERR_PTR(-ENOMEM);
+	i2c_dev->adap = adap;
+
+	spin_lock(&i2c_dev_list_lock);
+	list_add_tail(&i2c_dev->list, &i2c_dev_list);
+	spin_unlock(&i2c_dev_list_lock);
+	return i2c_dev;
+}
+
+static void put_i2c_dev(struct i2c_dev *i2c_dev, bool del_cdev)
+{
+	spin_lock(&i2c_dev_list_lock);
+	list_del(&i2c_dev->list);
+	spin_unlock(&i2c_dev_list_lock);
+	if (del_cdev)
+		cdev_device_del(&i2c_dev->cdev, &i2c_dev->dev);
+	put_device(&i2c_dev->dev);
+}
+
+static ssize_t name_show(struct device *dev,
+			 struct device_attribute *attr, char *buf)
+{
+	struct i2c_dev *i2c_dev = i2c_dev_get_by_minor(MINOR(dev->devt));
+
+	if (!i2c_dev)
+		return -ENODEV;
+	return sysfs_emit(buf, "%s\n", i2c_dev->adap->name);
+}
+static DEVICE_ATTR_RO(name);
+
+static struct attribute *i2c_attrs[] = {
+	&dev_attr_name.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(i2c);
+
+/* ------------------------------------------------------------------------- */
+
+/*
+ * After opening an instance of this character special file, a file
+ * descriptor starts out associated only with an i2c_adapter (and bus).
+ *
+ * Using the I2C_RDWR ioctl(), you can then *immediately* issue i2c_msg
+ * traffic to any devices on the bus used by that adapter.  That's because
+ * the i2c_msg vectors embed all the addressing information they need, and
+ * are submitted directly to an i2c_adapter.  However, SMBus-only adapters
+ * don't support that interface.
+ *
+ * To use read()/write() system calls on that file descriptor, or to use
+ * SMBus interfaces (and work with SMBus-only hosts!), you must first issue
+ * an I2C_SLAVE (or I2C_SLAVE_FORCE) ioctl.  That configures an anonymous
+ * (never registered) i2c_client so it holds the addressing information
+ * needed by those system calls and by this SMBus interface.
+ */
+
+static ssize_t i2cdev_read(struct file *file, char __user *buf, size_t count,
+		loff_t *offset)
+{
+	char *tmp;
+	int ret;
+
+	struct i2c_client *client = file->private_data;
+
+	/* Adapter must support I2C transfers */
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -EOPNOTSUPP;
+
+	if (count > 8192)
+		count = 8192;
+
+	tmp = kzalloc(count, GFP_KERNEL);
+	if (tmp == NULL)
+		return -ENOMEM;
+
+	pr_debug("i2c-%d reading %zu bytes.\n", iminor(file_inode(file)), count);
+
+	ret = i2c_master_recv(client, tmp, count);
+	if (ret >= 0)
+		if (copy_to_user(buf, tmp, ret))
+			ret = -EFAULT;
+	kfree(tmp);
+	return ret;
+}
+
+static ssize_t i2cdev_write(struct file *file, const char __user *buf,
+		size_t count, loff_t *offset)
+{
+	int ret;
+	char *tmp;
+	struct i2c_client *client = file->private_data;
+
+	/* Adapter must support I2C transfers */
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -EOPNOTSUPP;
+
+	if (count > 8192)
+		count = 8192;
+
+	tmp = memdup_user(buf, count);
+	if (IS_ERR(tmp))
+		return PTR_ERR(tmp);
+
+	pr_debug("i2c-%d writing %zu bytes.\n", iminor(file_inode(file)), count);
+
+	ret = i2c_master_send(client, tmp, count);
+	kfree(tmp);
+	return ret;
+}
+
+static int i2cdev_check(struct device *dev, void *addrp)
+{
+	struct i2c_client *client = i2c_verify_client(dev);
+
+	if (!client || client->addr != *(unsigned int *)addrp)
+		return 0;
+
+	return dev->driver ? -EBUSY : 0;
+}
+
+/* walk up mux tree */
+static int i2cdev_check_mux_parents(struct i2c_adapter *adapter, int addr)
+{
+	struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);
+	int result;
+
+	result = device_for_each_child(&adapter->dev, &addr, i2cdev_check);
+	if (!result && parent)
+		result = i2cdev_check_mux_parents(parent, addr);
+
+	return result;
+}
+
+/* recurse down mux tree */
+static int i2cdev_check_mux_children(struct device *dev, void *addrp)
+{
+	int result;
+
+	if (dev->type == &i2c_adapter_type)
+		result = device_for_each_child(dev, addrp,
+						i2cdev_check_mux_children);
+	else
+		result = i2cdev_check(dev, addrp);
+
+	return result;
+}
+
+/* This address checking function differs from the one in i2c-core
+   in that it considers an address with a registered device, but no
+   driver bound to it, as NOT busy. */
+static int i2cdev_check_addr(struct i2c_adapter *adapter, unsigned int addr)
+{
+	struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);
+	int result = 0;
+
+	if (parent)
+		result = i2cdev_check_mux_parents(parent, addr);
+
+	if (!result)
+		result = device_for_each_child(&adapter->dev, &addr,
+						i2cdev_check_mux_children);
+
+	return result;
+}
+
+static noinline int i2cdev_ioctl_rdwr(struct i2c_client *client,
+		unsigned nmsgs, struct i2c_msg *msgs)
+{
+	u8 __user **data_ptrs;
+	int i, res;
+
+	/* Adapter must support I2C transfers */
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -EOPNOTSUPP;
+
+	data_ptrs = kmalloc_array(nmsgs, sizeof(u8 __user *), GFP_KERNEL);
+	if (!data_ptrs)
+		return -ENOMEM;
+
+	res = 0;
+	for (i = 0; i < nmsgs; i++) {
+		/* Limit the size of the message to a sane amount */
+		if (msgs[i].len > 8192) {
+			res = -EINVAL;
+			break;
+		}
+
+		data_ptrs[i] = (u8 __user *)msgs[i].buf;
+		msgs[i].buf = memdup_user(data_ptrs[i], msgs[i].len);
+		if (IS_ERR(msgs[i].buf)) {
+			res = PTR_ERR(msgs[i].buf);
+			break;
+		}
+		/* memdup_user allocates with GFP_KERNEL, so DMA is ok */
+		msgs[i].flags |= I2C_M_DMA_SAFE;
+
+		/*
+		 * If the message length is received from the slave (similar
+		 * to SMBus block read), we must ensure that the buffer will
+		 * be large enough to cope with a message length of
+		 * I2C_SMBUS_BLOCK_MAX as this is the maximum underlying bus
+		 * drivers allow. The first byte in the buffer must be
+		 * pre-filled with the number of extra bytes, which must be
+		 * at least one to hold the message length, but can be
+		 * greater (for example to account for a checksum byte at
+		 * the end of the message.)
+		 */
+		if (msgs[i].flags & I2C_M_RECV_LEN) {
+			if (!(msgs[i].flags & I2C_M_RD) ||
+			    msgs[i].len < 1 || msgs[i].buf[0] < 1 ||
+			    msgs[i].len < msgs[i].buf[0] +
+					     I2C_SMBUS_BLOCK_MAX) {
+				i++;
+				res = -EINVAL;
+				break;
+			}
+
+			msgs[i].len = msgs[i].buf[0];
+		}
+	}
+	if (res < 0) {
+		int j;
+		for (j = 0; j < i; ++j)
+			kfree(msgs[j].buf);
+		kfree(data_ptrs);
+		return res;
+	}
+
+	res = i2c_transfer(client->adapter, msgs, nmsgs);
+	while (i-- > 0) {
+		if (res >= 0 && (msgs[i].flags & I2C_M_RD)) {
+			if (copy_to_user(data_ptrs[i], msgs[i].buf,
+					 msgs[i].len))
+				res = -EFAULT;
+		}
+		kfree(msgs[i].buf);
+	}
+	kfree(data_ptrs);
+	return res;
+}
+
+static noinline int i2cdev_ioctl_smbus(struct i2c_client *client,
+		u8 read_write, u8 command, u32 size,
+		union i2c_smbus_data __user *data)
+{
+	union i2c_smbus_data temp = {};
+	int datasize, res;
+
+	if ((size != I2C_SMBUS_BYTE) &&
+	    (size != I2C_SMBUS_QUICK) &&
+	    (size != I2C_SMBUS_BYTE_DATA) &&
+	    (size != I2C_SMBUS_WORD_DATA) &&
+	    (size != I2C_SMBUS_PROC_CALL) &&
+	    (size != I2C_SMBUS_BLOCK_DATA) &&
+	    (size != I2C_SMBUS_I2C_BLOCK_BROKEN) &&
+	    (size != I2C_SMBUS_I2C_BLOCK_DATA) &&
+	    (size != I2C_SMBUS_BLOCK_PROC_CALL)) {
+		dev_dbg(&client->adapter->dev,
+			"size out of range (%x) in ioctl I2C_SMBUS.\n",
+			size);
+		return -EINVAL;
+	}
+	/* Note that I2C_SMBUS_READ and I2C_SMBUS_WRITE are 0 and 1,
+	   so the check is valid if size==I2C_SMBUS_QUICK too. */
+	if ((read_write != I2C_SMBUS_READ) &&
+	    (read_write != I2C_SMBUS_WRITE)) {
+		dev_dbg(&client->adapter->dev,
+			"read_write out of range (%x) in ioctl I2C_SMBUS.\n",
+			read_write);
+		return -EINVAL;
+	}
+
+	/* Note that command values are always valid! */
+
+	if ((size == I2C_SMBUS_QUICK) ||
+	    ((size == I2C_SMBUS_BYTE) &&
+	    (read_write == I2C_SMBUS_WRITE)))
+		/* These are special: we do not use data */
+		return i2c_smbus_xfer(client->adapter, client->addr,
+				      client->flags, read_write,
+				      command, size, NULL);
+
+	if (data == NULL) {
+		dev_dbg(&client->adapter->dev,
+			"data is NULL pointer in ioctl I2C_SMBUS.\n");
+		return -EINVAL;
+	}
+
+	if ((size == I2C_SMBUS_BYTE_DATA) ||
+	    (size == I2C_SMBUS_BYTE))
+		datasize = sizeof(data->byte);
+	else if ((size == I2C_SMBUS_WORD_DATA) ||
+		 (size == I2C_SMBUS_PROC_CALL))
+		datasize = sizeof(data->word);
+	else /* size == smbus block, i2c block, or block proc. call */
+		datasize = sizeof(data->block);
+
+	if ((size == I2C_SMBUS_PROC_CALL) ||
+	    (size == I2C_SMBUS_BLOCK_PROC_CALL) ||
+	    (size == I2C_SMBUS_I2C_BLOCK_DATA) ||
+	    (read_write == I2C_SMBUS_WRITE)) {
+		if (copy_from_user(&temp, data, datasize))
+			return -EFAULT;
+	}
+	if (size == I2C_SMBUS_I2C_BLOCK_BROKEN) {
+		/* Convert old I2C block commands to the new
+		   convention. This preserves binary compatibility. */
+		size = I2C_SMBUS_I2C_BLOCK_DATA;
+		if (read_write == I2C_SMBUS_READ)
+			temp.block[0] = I2C_SMBUS_BLOCK_MAX;
+	}
+	res = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
+	      read_write, command, size, &temp);
+	if (!res && ((size == I2C_SMBUS_PROC_CALL) ||
+		     (size == I2C_SMBUS_BLOCK_PROC_CALL) ||
+		     (read_write == I2C_SMBUS_READ))) {
+		if (copy_to_user(data, &temp, datasize))
+			return -EFAULT;
+	}
+	return res;
+}
+
+static long i2cdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	struct i2c_client *client = file->private_data;
+	unsigned long funcs;
+
+	dev_dbg(&client->adapter->dev, "ioctl, cmd=0x%02x, arg=0x%02lx\n",
+		cmd, arg);
+
+	switch (cmd) {
+	case I2C_SLAVE:
+	case I2C_SLAVE_FORCE:
+		if ((arg > 0x3ff) ||
+		    (((client->flags & I2C_M_TEN) == 0) && arg > 0x7f))
+			return -EINVAL;
+		if (cmd == I2C_SLAVE && i2cdev_check_addr(client->adapter, arg))
+			return -EBUSY;
+		/* REVISIT: address could become busy later */
+		client->addr = arg;
+		return 0;
+	case I2C_TENBIT:
+		if (arg)
+			client->flags |= I2C_M_TEN;
+		else
+			client->flags &= ~I2C_M_TEN;
+		return 0;
+	case I2C_PEC:
+		/*
+		 * Setting the PEC flag here won't affect kernel drivers,
+		 * which will be using the i2c_client node registered with
+		 * the driver model core.  Likewise, when that client has
+		 * the PEC flag already set, the i2c-dev driver won't see
+		 * (or use) this setting.
+		 */
+		if (arg)
+			client->flags |= I2C_CLIENT_PEC;
+		else
+			client->flags &= ~I2C_CLIENT_PEC;
+		return 0;
+	case I2C_FUNCS:
+		funcs = i2c_get_functionality(client->adapter);
+		return put_user(funcs, (unsigned long __user *)arg);
+
+	case I2C_RDWR: {
+		struct i2c_rdwr_ioctl_data rdwr_arg;
+		struct i2c_msg *rdwr_pa;
+		int res;
+
+		if (copy_from_user(&rdwr_arg,
+				   (struct i2c_rdwr_ioctl_data __user *)arg,
+				   sizeof(rdwr_arg)))
+			return -EFAULT;
+
+		if (!rdwr_arg.msgs || rdwr_arg.nmsgs == 0)
+			return -EINVAL;
+
+		/*
+		 * Put an arbitrary limit on the number of messages that can
+		 * be sent at once
+		 */
+		if (rdwr_arg.nmsgs > I2C_RDWR_IOCTL_MAX_MSGS)
+			return -EINVAL;
+
+		rdwr_pa = memdup_array_user(rdwr_arg.msgs,
+					    rdwr_arg.nmsgs, sizeof(struct i2c_msg));
+		if (IS_ERR(rdwr_pa))
+			return PTR_ERR(rdwr_pa);
+
+		res = i2cdev_ioctl_rdwr(client, rdwr_arg.nmsgs, rdwr_pa);
+		kfree(rdwr_pa);
+		return res;
+	}
+
+	case I2C_SMBUS: {
+		struct i2c_smbus_ioctl_data data_arg;
+		if (copy_from_user(&data_arg,
+				   (struct i2c_smbus_ioctl_data __user *) arg,
+				   sizeof(struct i2c_smbus_ioctl_data)))
+			return -EFAULT;
+		return i2cdev_ioctl_smbus(client, data_arg.read_write,
+					  data_arg.command,
+					  data_arg.size,
+					  data_arg.data);
+	}
+	case I2C_RETRIES:
+		if (arg > INT_MAX)
+			return -EINVAL;
+
+		client->adapter->retries = arg;
+		break;
+	case I2C_TIMEOUT:
+		/*
+		 * For historical reasons, user-space sets the timeout value in
+		 * units of 10 ms.
+		 */
+		if (arg > INT_MAX / 10)
+			return -EINVAL;
+
+		client->adapter->timeout = msecs_to_jiffies(arg * 10);
+		break;
+	default:
+		/* NOTE:  returning a fault code here could cause trouble
+		 * in buggy userspace code.  Some old kernel bugs returned
+		 * zero in this case, and userspace code might accidentally
+		 * have depended on that bug.
+		 */
+		return -ENOTTY;
+	}
+	return 0;
+}
+
+#ifdef CONFIG_COMPAT
+
+struct i2c_smbus_ioctl_data32 {
+	u8 read_write;
+	u8 command;
+	u32 size;
+	compat_caddr_t data; /* union i2c_smbus_data *data */
+};
+
+struct i2c_msg32 {
+	u16 addr;
+	u16 flags;
+	u16 len;
+	compat_caddr_t buf;
+};
+
+struct i2c_rdwr_ioctl_data32 {
+	compat_caddr_t msgs; /* struct i2c_msg __user *msgs */
+	u32 nmsgs;
+};
+
+static long compat_i2cdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	struct i2c_client *client = file->private_data;
+	unsigned long funcs;
+	switch (cmd) {
+	case I2C_FUNCS:
+		funcs = i2c_get_functionality(client->adapter);
+		return put_user(funcs, (compat_ulong_t __user *)arg);
+	case I2C_RDWR: {
+		struct i2c_rdwr_ioctl_data32 rdwr_arg;
+		struct i2c_msg32 __user *p;
+		struct i2c_msg *rdwr_pa;
+		int i, res;
+
+		if (copy_from_user(&rdwr_arg,
+				   (struct i2c_rdwr_ioctl_data32 __user *)arg,
+				   sizeof(rdwr_arg)))
+			return -EFAULT;
+
+		if (!rdwr_arg.msgs || rdwr_arg.nmsgs == 0)
+			return -EINVAL;
+
+		if (rdwr_arg.nmsgs > I2C_RDWR_IOCTL_MAX_MSGS)
+			return -EINVAL;
+
+		rdwr_pa = kmalloc_objs(struct i2c_msg, rdwr_arg.nmsgs);
+		if (!rdwr_pa)
+			return -ENOMEM;
+
+		p = compat_ptr(rdwr_arg.msgs);
+		for (i = 0; i < rdwr_arg.nmsgs; i++) {
+			struct i2c_msg32 umsg;
+			if (copy_from_user(&umsg, p + i, sizeof(umsg))) {
+				kfree(rdwr_pa);
+				return -EFAULT;
+			}
+			rdwr_pa[i] = (struct i2c_msg) {
+				.addr = umsg.addr,
+				.flags = umsg.flags,
+				.len = umsg.len,
+				.buf = (__force __u8 *)compat_ptr(umsg.buf),
+			};
+		}
+
+		res = i2cdev_ioctl_rdwr(client, rdwr_arg.nmsgs, rdwr_pa);
+		kfree(rdwr_pa);
+		return res;
+	}
+	case I2C_SMBUS: {
+		struct i2c_smbus_ioctl_data32	data32;
+		if (copy_from_user(&data32,
+				   (void __user *) arg,
+				   sizeof(data32)))
+			return -EFAULT;
+		return i2cdev_ioctl_smbus(client, data32.read_write,
+					  data32.command,
+					  data32.size,
+					  compat_ptr(data32.data));
+	}
+	default:
+		return i2cdev_ioctl(file, cmd, arg);
+	}
+}
+#else
+#define compat_i2cdev_ioctl NULL
+#endif
+
+static int i2cdev_open(struct inode *inode, struct file *file)
+{
+	unsigned int minor = iminor(inode);
+	struct i2c_client *client;
+	struct i2c_adapter *adap;
+
+	adap = i2c_get_adapter(minor);
+	if (!adap)
+		return -ENODEV;
+
+	/* This creates an anonymous i2c_client, which may later be
+	 * pointed to some address using I2C_SLAVE or I2C_SLAVE_FORCE.
+	 *
+	 * This client is ** NEVER REGISTERED ** with the driver model
+	 * or I2C core code!!  It just holds private copies of addressing
+	 * information and maybe a PEC flag.
+	 */
+	client = kzalloc_obj(*client);
+	if (!client) {
+		i2c_put_adapter(adap);
+		return -ENOMEM;
+	}
+	snprintf(client->name, I2C_NAME_SIZE, "i2c-dev %d", adap->nr);
+
+	client->adapter = adap;
+	file->private_data = client;
+
+	return 0;
+}
+
+static int i2cdev_release(struct inode *inode, struct file *file)
+{
+	struct i2c_client *client = file->private_data;
+
+	i2c_put_adapter(client->adapter);
+	kfree(client);
+	file->private_data = NULL;
+
+	return 0;
+}
+
+static const struct file_operations i2cdev_fops = {
+	.owner		= THIS_MODULE,
+	.read		= i2cdev_read,
+	.write		= i2cdev_write,
+	.unlocked_ioctl	= i2cdev_ioctl,
+	.compat_ioctl	= compat_i2cdev_ioctl,
+	.open		= i2cdev_open,
+	.release	= i2cdev_release,
+};
+
+/* ------------------------------------------------------------------------- */
+
+static const struct class i2c_dev_class = {
+	.name = "i2c-dev",
+	.dev_groups = i2c_groups,
+};
+
+static void i2cdev_dev_release(struct device *dev)
+{
+	struct i2c_dev *i2c_dev;
+
+	i2c_dev = container_of(dev, struct i2c_dev, dev);
+	kfree(i2c_dev);
+}
+
+static int i2cdev_attach_adapter(struct device *dev)
+{
+	struct i2c_adapter *adap;
+	struct i2c_dev *i2c_dev;
+	int res;
+
+	if (dev->type != &i2c_adapter_type)
+		return NOTIFY_DONE;
+	adap = to_i2c_adapter(dev);
+
+	i2c_dev = get_free_i2c_dev(adap);
+	if (IS_ERR(i2c_dev))
+		return NOTIFY_DONE;
+
+	cdev_init(&i2c_dev->cdev, &i2cdev_fops);
+	i2c_dev->cdev.owner = THIS_MODULE;
+
+	device_initialize(&i2c_dev->dev);
+	i2c_dev->dev.devt = MKDEV(I2C_MAJOR, adap->nr);
+	i2c_dev->dev.class = &i2c_dev_class;
+	i2c_dev->dev.parent = &adap->dev;
+	i2c_dev->dev.release = i2cdev_dev_release;
+
+	res = dev_set_name(&i2c_dev->dev, "i2c-%d", adap->nr);
+	if (res)
+		goto err_put_i2c_dev;
+
+	res = cdev_device_add(&i2c_dev->cdev, &i2c_dev->dev);
+	if (res)
+		goto err_put_i2c_dev;
+
+	pr_debug("adapter [%s] registered as minor %d\n", adap->name, adap->nr);
+	return NOTIFY_OK;
+
+err_put_i2c_dev:
+	put_i2c_dev(i2c_dev, false);
+	return NOTIFY_DONE;
+}
+
+static int i2cdev_detach_adapter(struct device *dev)
+{
+	struct i2c_adapter *adap;
+	struct i2c_dev *i2c_dev;
+
+	if (dev->type != &i2c_adapter_type)
+		return NOTIFY_DONE;
+	adap = to_i2c_adapter(dev);
+
+	i2c_dev = i2c_dev_get_by_minor(adap->nr);
+	if (!i2c_dev) /* attach_adapter must have failed */
+		return NOTIFY_DONE;
+
+	put_i2c_dev(i2c_dev, true);
+
+	pr_debug("adapter [%s] unregistered\n", adap->name);
+	return NOTIFY_OK;
+}
+
+static int i2cdev_notifier_call(struct notifier_block *nb, unsigned long action,
+			 void *data)
+{
+	struct device *dev = data;
+
+	switch (action) {
+	case BUS_NOTIFY_ADD_DEVICE:
+		return i2cdev_attach_adapter(dev);
+	case BUS_NOTIFY_DEL_DEVICE:
+		return i2cdev_detach_adapter(dev);
+	}
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block i2cdev_notifier = {
+	.notifier_call = i2cdev_notifier_call,
+};
+
+/* ------------------------------------------------------------------------- */
+
+static int __init i2c_dev_attach_adapter(struct device *dev, void *dummy)
+{
+	i2cdev_attach_adapter(dev);
+	return 0;
+}
+
+static int __exit i2c_dev_detach_adapter(struct device *dev, void *dummy)
+{
+	i2cdev_detach_adapter(dev);
+	return 0;
+}
+
+/*
+ * module load/unload record keeping
+ */
+
+static int __init i2c_dev_init(void)
+{
+	int res;
+
+	pr_info("i2c /dev entries driver\n");
+
+	res = register_chrdev_region(MKDEV(I2C_MAJOR, 0), I2C_MINORS, "i2c");
+	if (res)
+		goto out;
+
+	res = class_register(&i2c_dev_class);
+	if (res)
+		goto out_unreg_chrdev;
+
+	/* Keep track of adapters which will be added or removed later */
+	res = bus_register_notifier(&i2c_bus_type, &i2cdev_notifier);
+	if (res)
+		goto out_unreg_class;
+
+	/* Bind to already existing adapters right away */
+	i2c_for_each_dev(NULL, i2c_dev_attach_adapter);
+
+	return 0;
+
+out_unreg_class:
+	class_unregister(&i2c_dev_class);
+out_unreg_chrdev:
+	unregister_chrdev_region(MKDEV(I2C_MAJOR, 0), I2C_MINORS);
+out:
+	pr_err("Driver Initialisation failed\n");
+	return res;
+}
+
+static void __exit i2c_dev_exit(void)
+{
+	bus_unregister_notifier(&i2c_bus_type, &i2cdev_notifier);
+	i2c_for_each_dev(NULL, i2c_dev_detach_adapter);
+	class_unregister(&i2c_dev_class);
+	unregister_chrdev_region(MKDEV(I2C_MAJOR, 0), I2C_MINORS);
+}
+
+MODULE_AUTHOR("Frodo Looijaard <frodol@dds.nl>");
+MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
+MODULE_DESCRIPTION("I2C /dev entries driver");
+MODULE_LICENSE("GPL");
+
+module_init(i2c_dev_init);
+module_exit(i2c_dev_exit);