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, 794 insertions, 0 deletions

diff --git a/drivers/usb/misc/ldusb.c b/drivers/usb/misc/ldusb.c
new file mode 100644
index 000000000..71132a15e
--- /dev/null
+++ b/drivers/usb/misc/ldusb.c
@@ -0,0 +1,794 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Generic USB driver for report based interrupt in/out devices
+ * like LD Didactic's USB devices. LD Didactic's USB devices are
+ * HID devices which do not use HID report definitons (they use
+ * raw interrupt in and our reports only for communication).
+ *
+ * This driver uses a ring buffer for time critical reading of
+ * interrupt in reports and provides read and write methods for
+ * raw interrupt reports (similar to the Windows HID driver).
+ * Devices based on the book USB COMPLETE by Jan Axelson may need
+ * such a compatibility to the Windows HID driver.
+ *
+ * Copyright (C) 2005 Michael Hund <mhund@ld-didactic.de>
+ *
+ * Derived from Lego USB Tower driver
+ * Copyright (C) 2003 David Glance <advidgsf@sourceforge.net>
+ *		 2001-2004 Juergen Stuber <starblue@users.sourceforge.net>
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+
+#include <linux/uaccess.h>
+#include <linux/input.h>
+#include <linux/usb.h>
+#include <linux/poll.h>
+
+/* Define these values to match your devices */
+#define USB_VENDOR_ID_LD		0x0f11	/* USB Vendor ID of LD Didactic GmbH */
+#define USB_DEVICE_ID_LD_CASSY		0x1000	/* USB Product ID of CASSY-S modules with 8 bytes endpoint size */
+#define USB_DEVICE_ID_LD_CASSY2		0x1001	/* USB Product ID of CASSY-S modules with 64 bytes endpoint size */
+#define USB_DEVICE_ID_LD_POCKETCASSY	0x1010	/* USB Product ID of Pocket-CASSY */
+#define USB_DEVICE_ID_LD_POCKETCASSY2	0x1011	/* USB Product ID of Pocket-CASSY 2 (reserved) */
+#define USB_DEVICE_ID_LD_MOBILECASSY	0x1020	/* USB Product ID of Mobile-CASSY */
+#define USB_DEVICE_ID_LD_MOBILECASSY2	0x1021	/* USB Product ID of Mobile-CASSY 2 (reserved) */
+#define USB_DEVICE_ID_LD_MICROCASSYVOLTAGE	0x1031	/* USB Product ID of Micro-CASSY Voltage */
+#define USB_DEVICE_ID_LD_MICROCASSYCURRENT	0x1032	/* USB Product ID of Micro-CASSY Current */
+#define USB_DEVICE_ID_LD_MICROCASSYTIME		0x1033	/* USB Product ID of Micro-CASSY Time (reserved) */
+#define USB_DEVICE_ID_LD_MICROCASSYTEMPERATURE	0x1035	/* USB Product ID of Micro-CASSY Temperature */
+#define USB_DEVICE_ID_LD_MICROCASSYPH		0x1038	/* USB Product ID of Micro-CASSY pH */
+#define USB_DEVICE_ID_LD_POWERANALYSERCASSY	0x1040	/* USB Product ID of Power Analyser CASSY */
+#define USB_DEVICE_ID_LD_CONVERTERCONTROLLERCASSY	0x1042	/* USB Product ID of Converter Controller CASSY */
+#define USB_DEVICE_ID_LD_MACHINETESTCASSY	0x1043	/* USB Product ID of Machine Test CASSY */
+#define USB_DEVICE_ID_LD_JWM		0x1080	/* USB Product ID of Joule and Wattmeter */
+#define USB_DEVICE_ID_LD_DMMP		0x1081	/* USB Product ID of Digital Multimeter P (reserved) */
+#define USB_DEVICE_ID_LD_UMIP		0x1090	/* USB Product ID of UMI P */
+#define USB_DEVICE_ID_LD_UMIC		0x10A0	/* USB Product ID of UMI C */
+#define USB_DEVICE_ID_LD_UMIB		0x10B0	/* USB Product ID of UMI B */
+#define USB_DEVICE_ID_LD_XRAY		0x1100	/* USB Product ID of X-Ray Apparatus 55481 */
+#define USB_DEVICE_ID_LD_XRAY2		0x1101	/* USB Product ID of X-Ray Apparatus 554800 */
+#define USB_DEVICE_ID_LD_XRAYCT		0x1110	/* USB Product ID of X-Ray Apparatus CT 554821*/
+#define USB_DEVICE_ID_LD_VIDEOCOM	0x1200	/* USB Product ID of VideoCom */
+#define USB_DEVICE_ID_LD_MOTOR		0x1210	/* USB Product ID of Motor (reserved) */
+#define USB_DEVICE_ID_LD_COM3LAB	0x2000	/* USB Product ID of COM3LAB */
+#define USB_DEVICE_ID_LD_TELEPORT	0x2010	/* USB Product ID of Terminal Adapter */
+#define USB_DEVICE_ID_LD_NETWORKANALYSER 0x2020	/* USB Product ID of Network Analyser */
+#define USB_DEVICE_ID_LD_POWERCONTROL	0x2030	/* USB Product ID of Converter Control Unit */
+#define USB_DEVICE_ID_LD_MACHINETEST	0x2040	/* USB Product ID of Machine Test System */
+#define USB_DEVICE_ID_LD_MOSTANALYSER	0x2050	/* USB Product ID of MOST Protocol Analyser */
+#define USB_DEVICE_ID_LD_MOSTANALYSER2	0x2051	/* USB Product ID of MOST Protocol Analyser 2 */
+#define USB_DEVICE_ID_LD_ABSESP		0x2060	/* USB Product ID of ABS ESP */
+#define USB_DEVICE_ID_LD_AUTODATABUS	0x2070	/* USB Product ID of Automotive Data Buses */
+#define USB_DEVICE_ID_LD_MCT		0x2080	/* USB Product ID of Microcontroller technique */
+#define USB_DEVICE_ID_LD_HYBRID		0x2090	/* USB Product ID of Automotive Hybrid */
+#define USB_DEVICE_ID_LD_HEATCONTROL	0x20A0	/* USB Product ID of Heat control */
+
+#ifdef CONFIG_USB_DYNAMIC_MINORS
+#define USB_LD_MINOR_BASE	0
+#else
+#define USB_LD_MINOR_BASE	176
+#endif
+
+/* table of devices that work with this driver */
+static const struct usb_device_id ld_usb_table[] = {
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_CASSY) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_CASSY2) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_POCKETCASSY) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_POCKETCASSY2) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MOBILECASSY) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MOBILECASSY2) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MICROCASSYVOLTAGE) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MICROCASSYCURRENT) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MICROCASSYTIME) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MICROCASSYTEMPERATURE) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MICROCASSYPH) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_POWERANALYSERCASSY) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_CONVERTERCONTROLLERCASSY) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MACHINETESTCASSY) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_JWM) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_DMMP) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_UMIP) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_UMIC) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_UMIB) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_XRAY) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_XRAY2) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_VIDEOCOM) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MOTOR) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_COM3LAB) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_TELEPORT) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_NETWORKANALYSER) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_POWERCONTROL) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MACHINETEST) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MOSTANALYSER) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MOSTANALYSER2) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_ABSESP) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_AUTODATABUS) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_MCT) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_HYBRID) },
+	{ USB_DEVICE(USB_VENDOR_ID_LD, USB_DEVICE_ID_LD_HEATCONTROL) },
+	{ }					/* Terminating entry */
+};
+MODULE_DEVICE_TABLE(usb, ld_usb_table);
+MODULE_AUTHOR("Michael Hund <mhund@ld-didactic.de>");
+MODULE_DESCRIPTION("LD USB Driver");
+MODULE_LICENSE("GPL");
+
+/* All interrupt in transfers are collected in a ring buffer to
+ * avoid racing conditions and get better performance of the driver.
+ */
+static int ring_buffer_size = 128;
+module_param(ring_buffer_size, int, 0000);
+MODULE_PARM_DESC(ring_buffer_size, "Read ring buffer size in reports");
+
+/* The write_buffer can contain more than one interrupt out transfer.
+ */
+static int write_buffer_size = 10;
+module_param(write_buffer_size, int, 0000);
+MODULE_PARM_DESC(write_buffer_size, "Write buffer size in reports");
+
+/* As of kernel version 2.6.4 ehci-hcd uses an
+ * "only one interrupt transfer per frame" shortcut
+ * to simplify the scheduling of periodic transfers.
+ * This conflicts with our standard 1ms intervals for in and out URBs.
+ * We use default intervals of 2ms for in and 2ms for out transfers,
+ * which should be fast enough.
+ * Increase the interval to allow more devices that do interrupt transfers,
+ * or set to 1 to use the standard interval from the endpoint descriptors.
+ */
+static int min_interrupt_in_interval = 2;
+module_param(min_interrupt_in_interval, int, 0000);
+MODULE_PARM_DESC(min_interrupt_in_interval, "Minimum interrupt in interval in ms");
+
+static int min_interrupt_out_interval = 2;
+module_param(min_interrupt_out_interval, int, 0000);
+MODULE_PARM_DESC(min_interrupt_out_interval, "Minimum interrupt out interval in ms");
+
+/* Structure to hold all of our device specific stuff */
+struct ld_usb {
+	struct kref		kref;
+	struct mutex		mutex;		/* locks this structure */
+	struct usb_interface	*intf;		/* save off the usb interface pointer */
+	unsigned long		disconnected:1;
+
+	int			open_count;	/* number of times this port has been opened */
+
+	char			*ring_buffer;
+	unsigned int		ring_head;
+	unsigned int		ring_tail;
+
+	wait_queue_head_t	read_wait;
+	wait_queue_head_t	write_wait;
+
+	char			*interrupt_in_buffer;
+	struct usb_endpoint_descriptor *interrupt_in_endpoint;
+	struct urb		*interrupt_in_urb;
+	int			interrupt_in_interval;
+	size_t			interrupt_in_endpoint_size;
+	int			interrupt_in_running;
+	int			interrupt_in_done;
+	int			buffer_overflow;
+	spinlock_t		rbsl;
+
+	char			*interrupt_out_buffer;
+	struct usb_endpoint_descriptor *interrupt_out_endpoint;
+	struct urb		*interrupt_out_urb;
+	int			interrupt_out_interval;
+	size_t			interrupt_out_endpoint_size;
+	int			interrupt_out_busy;
+};
+
+static struct usb_driver ld_usb_driver;
+
+/*
+ *	ld_usb_abort_transfers
+ *      aborts transfers and frees associated data structures
+ */
+static void ld_usb_abort_transfers(struct ld_usb *dev)
+{
+	/* shutdown transfer */
+	if (dev->interrupt_in_running) {
+		dev->interrupt_in_running = 0;
+		usb_kill_urb(dev->interrupt_in_urb);
+	}
+	if (dev->interrupt_out_busy)
+		usb_kill_urb(dev->interrupt_out_urb);
+}
+
+/*
+ *	ld_usb_delete
+ */
+static void ld_usb_delete(struct kref *kref)
+{
+	struct ld_usb *dev = container_of(kref, struct ld_usb, kref);
+
+	/* free data structures */
+	usb_free_urb(dev->interrupt_in_urb);
+	usb_free_urb(dev->interrupt_out_urb);
+	kfree(dev->ring_buffer);
+	kfree(dev->interrupt_in_buffer);
+	kfree(dev->interrupt_out_buffer);
+	kfree(dev);
+}
+
+/*
+ *	ld_usb_interrupt_in_callback
+ */
+static void ld_usb_interrupt_in_callback(struct urb *urb)
+{
+	struct ld_usb *dev = urb->context;
+	size_t *actual_buffer;
+	unsigned int next_ring_head;
+	int status = urb->status;
+	unsigned long flags;
+	int retval;
+
+	if (status) {
+		if (status == -ENOENT ||
+		    status == -ECONNRESET ||
+		    status == -ESHUTDOWN) {
+			goto exit;
+		} else {
+			dev_dbg(&dev->intf->dev,
+				"%s: nonzero status received: %d\n", __func__,
+				status);
+			spin_lock_irqsave(&dev->rbsl, flags);
+			goto resubmit; /* maybe we can recover */
+		}
+	}
+
+	spin_lock_irqsave(&dev->rbsl, flags);
+	if (urb->actual_length > 0) {
+		next_ring_head = (dev->ring_head+1) % ring_buffer_size;
+		if (next_ring_head != dev->ring_tail) {
+			actual_buffer = (size_t *)(dev->ring_buffer + dev->ring_head * (sizeof(size_t)+dev->interrupt_in_endpoint_size));
+			/* actual_buffer gets urb->actual_length + interrupt_in_buffer */
+			*actual_buffer = urb->actual_length;
+			memcpy(actual_buffer+1, dev->interrupt_in_buffer, urb->actual_length);
+			dev->ring_head = next_ring_head;
+			dev_dbg(&dev->intf->dev, "%s: received %d bytes\n",
+				__func__, urb->actual_length);
+		} else {
+			dev_warn(&dev->intf->dev,
+				 "Ring buffer overflow, %d bytes dropped\n",
+				 urb->actual_length);
+			dev->buffer_overflow = 1;
+		}
+	}
+
+resubmit:
+	/* resubmit if we're still running */
+	if (dev->interrupt_in_running && !dev->buffer_overflow) {
+		retval = usb_submit_urb(dev->interrupt_in_urb, GFP_ATOMIC);
+		if (retval) {
+			dev_err(&dev->intf->dev,
+				"usb_submit_urb failed (%d)\n", retval);
+			dev->buffer_overflow = 1;
+		}
+	}
+	spin_unlock_irqrestore(&dev->rbsl, flags);
+exit:
+	dev->interrupt_in_done = 1;
+	wake_up_interruptible(&dev->read_wait);
+}
+
+/*
+ *	ld_usb_interrupt_out_callback
+ */
+static void ld_usb_interrupt_out_callback(struct urb *urb)
+{
+	struct ld_usb *dev = urb->context;
+	int status = urb->status;
+
+	/* sync/async unlink faults aren't errors */
+	if (status && !(status == -ENOENT ||
+			status == -ECONNRESET ||
+			status == -ESHUTDOWN))
+		dev_dbg(&dev->intf->dev,
+			"%s - nonzero write interrupt status received: %d\n",
+			__func__, status);
+
+	dev->interrupt_out_busy = 0;
+	wake_up_interruptible(&dev->write_wait);
+}
+
+/*
+ *	ld_usb_open
+ */
+static int ld_usb_open(struct inode *inode, struct file *file)
+{
+	struct ld_usb *dev;
+	int subminor;
+	int retval;
+	struct usb_interface *interface;
+
+	stream_open(inode, file);
+	subminor = iminor(inode);
+
+	interface = usb_find_interface(&ld_usb_driver, subminor);
+
+	if (!interface) {
+		printk(KERN_ERR "%s - error, can't find device for minor %d\n",
+		       __func__, subminor);
+		return -ENODEV;
+	}
+
+	dev = usb_get_intfdata(interface);
+
+	if (!dev)
+		return -ENODEV;
+
+	/* lock this device */
+	if (mutex_lock_interruptible(&dev->mutex))
+		return -ERESTARTSYS;
+
+	/* allow opening only once */
+	if (dev->open_count) {
+		retval = -EBUSY;
+		goto unlock_exit;
+	}
+	dev->open_count = 1;
+
+	/* initialize in direction */
+	dev->ring_head = 0;
+	dev->ring_tail = 0;
+	dev->buffer_overflow = 0;
+	usb_fill_int_urb(dev->interrupt_in_urb,
+			 interface_to_usbdev(interface),
+			 usb_rcvintpipe(interface_to_usbdev(interface),
+					dev->interrupt_in_endpoint->bEndpointAddress),
+			 dev->interrupt_in_buffer,
+			 dev->interrupt_in_endpoint_size,
+			 ld_usb_interrupt_in_callback,
+			 dev,
+			 dev->interrupt_in_interval);
+
+	dev->interrupt_in_running = 1;
+	dev->interrupt_in_done = 0;
+
+	retval = usb_submit_urb(dev->interrupt_in_urb, GFP_KERNEL);
+	if (retval) {
+		dev_err(&interface->dev, "Couldn't submit interrupt_in_urb %d\n", retval);
+		dev->interrupt_in_running = 0;
+		dev->open_count = 0;
+		goto unlock_exit;
+	}
+
+	kref_get(&dev->kref);
+
+	/* save device in the file's private structure */
+	file->private_data = dev;
+
+unlock_exit:
+	mutex_unlock(&dev->mutex);
+
+	return retval;
+}
+
+/*
+ *	ld_usb_release
+ */
+static int ld_usb_release(struct inode *inode, struct file *file)
+{
+	struct ld_usb *dev;
+	int retval = 0;
+
+	dev = file->private_data;
+
+	if (dev == NULL) {
+		retval = -ENODEV;
+		goto exit;
+	}
+
+	mutex_lock(&dev->mutex);
+
+	if (dev->disconnected)
+		goto unlock_exit;
+
+	/* wait until write transfer is finished */
+	if (dev->interrupt_out_busy)
+		wait_event_interruptible_timeout(dev->write_wait, !dev->interrupt_out_busy, 2 * HZ);
+	ld_usb_abort_transfers(dev);
+	dev->open_count = 0;
+
+unlock_exit:
+	mutex_unlock(&dev->mutex);
+	kref_put(&dev->kref, ld_usb_delete);
+exit:
+	return retval;
+}
+
+/*
+ *	ld_usb_poll
+ */
+static __poll_t ld_usb_poll(struct file *file, poll_table *wait)
+{
+	struct ld_usb *dev;
+	__poll_t mask = 0;
+
+	dev = file->private_data;
+
+	if (dev->disconnected)
+		return EPOLLERR | EPOLLHUP;
+
+	poll_wait(file, &dev->read_wait, wait);
+	poll_wait(file, &dev->write_wait, wait);
+
+	if (dev->ring_head != dev->ring_tail)
+		mask |= EPOLLIN | EPOLLRDNORM;
+	if (!dev->interrupt_out_busy)
+		mask |= EPOLLOUT | EPOLLWRNORM;
+
+	return mask;
+}
+
+/*
+ *	ld_usb_read
+ */
+static ssize_t ld_usb_read(struct file *file, char __user *buffer, size_t count,
+			   loff_t *ppos)
+{
+	struct ld_usb *dev;
+	size_t *actual_buffer;
+	size_t bytes_to_read;
+	int retval = 0;
+	int rv;
+
+	dev = file->private_data;
+
+	/* verify that we actually have some data to read */
+	if (count == 0)
+		goto exit;
+
+	/* lock this object */
+	if (mutex_lock_interruptible(&dev->mutex)) {
+		retval = -ERESTARTSYS;
+		goto exit;
+	}
+
+	/* verify that the device wasn't unplugged */
+	if (dev->disconnected) {
+		retval = -ENODEV;
+		printk(KERN_ERR "ldusb: No device or device unplugged %d\n", retval);
+		goto unlock_exit;
+	}
+
+	/* wait for data */
+	spin_lock_irq(&dev->rbsl);
+	while (dev->ring_head == dev->ring_tail) {
+		dev->interrupt_in_done = 0;
+		spin_unlock_irq(&dev->rbsl);
+		if (file->f_flags & O_NONBLOCK) {
+			retval = -EAGAIN;
+			goto unlock_exit;
+		}
+		retval = wait_event_interruptible(dev->read_wait, dev->interrupt_in_done);
+		if (retval < 0)
+			goto unlock_exit;
+
+		spin_lock_irq(&dev->rbsl);
+	}
+	spin_unlock_irq(&dev->rbsl);
+
+	/* actual_buffer contains actual_length + interrupt_in_buffer */
+	actual_buffer = (size_t *)(dev->ring_buffer + dev->ring_tail * (sizeof(size_t)+dev->interrupt_in_endpoint_size));
+	if (*actual_buffer > dev->interrupt_in_endpoint_size) {
+		retval = -EIO;
+		goto unlock_exit;
+	}
+	bytes_to_read = min(count, *actual_buffer);
+	if (bytes_to_read < *actual_buffer)
+		dev_warn(&dev->intf->dev, "Read buffer overflow, %zu bytes dropped\n",
+			 *actual_buffer-bytes_to_read);
+
+	/* copy one interrupt_in_buffer from ring_buffer into userspace */
+	if (copy_to_user(buffer, actual_buffer+1, bytes_to_read)) {
+		retval = -EFAULT;
+		goto unlock_exit;
+	}
+	retval = bytes_to_read;
+
+	spin_lock_irq(&dev->rbsl);
+	dev->ring_tail = (dev->ring_tail + 1) % ring_buffer_size;
+
+	if (dev->buffer_overflow) {
+		dev->buffer_overflow = 0;
+		spin_unlock_irq(&dev->rbsl);
+		rv = usb_submit_urb(dev->interrupt_in_urb, GFP_KERNEL);
+		if (rv < 0)
+			dev->buffer_overflow = 1;
+	} else {
+		spin_unlock_irq(&dev->rbsl);
+	}
+
+unlock_exit:
+	/* unlock the device */
+	mutex_unlock(&dev->mutex);
+
+exit:
+	return retval;
+}
+
+/*
+ *	ld_usb_write
+ */
+static ssize_t ld_usb_write(struct file *file, const char __user *buffer,
+			    size_t count, loff_t *ppos)
+{
+	struct ld_usb *dev;
+	size_t bytes_to_write;
+	int retval = 0;
+
+	dev = file->private_data;
+
+	/* verify that we actually have some data to write */
+	if (count == 0)
+		goto exit;
+
+	/* lock this object */
+	if (mutex_lock_interruptible(&dev->mutex)) {
+		retval = -ERESTARTSYS;
+		goto exit;
+	}
+
+	/* verify that the device wasn't unplugged */
+	if (dev->disconnected) {
+		retval = -ENODEV;
+		printk(KERN_ERR "ldusb: No device or device unplugged %d\n", retval);
+		goto unlock_exit;
+	}
+
+	/* wait until previous transfer is finished */
+	if (dev->interrupt_out_busy) {
+		if (file->f_flags & O_NONBLOCK) {
+			retval = -EAGAIN;
+			goto unlock_exit;
+		}
+		retval = wait_event_interruptible(dev->write_wait, !dev->interrupt_out_busy);
+		if (retval < 0) {
+			goto unlock_exit;
+		}
+	}
+
+	/* write the data into interrupt_out_buffer from userspace */
+	bytes_to_write = min(count, write_buffer_size*dev->interrupt_out_endpoint_size);
+	if (bytes_to_write < count)
+		dev_warn(&dev->intf->dev, "Write buffer overflow, %zu bytes dropped\n",
+			count - bytes_to_write);
+	dev_dbg(&dev->intf->dev, "%s: count = %zu, bytes_to_write = %zu\n",
+		__func__, count, bytes_to_write);
+
+	if (copy_from_user(dev->interrupt_out_buffer, buffer, bytes_to_write)) {
+		retval = -EFAULT;
+		goto unlock_exit;
+	}
+
+	if (dev->interrupt_out_endpoint == NULL) {
+		/* try HID_REQ_SET_REPORT=9 on control_endpoint instead of interrupt_out_endpoint */
+		retval = usb_control_msg(interface_to_usbdev(dev->intf),
+					 usb_sndctrlpipe(interface_to_usbdev(dev->intf), 0),
+					 9,
+					 USB_TYPE_CLASS | USB_RECIP_INTERFACE | USB_DIR_OUT,
+					 1 << 8, 0,
+					 dev->interrupt_out_buffer,
+					 bytes_to_write,
+					 USB_CTRL_SET_TIMEOUT);
+		if (retval < 0)
+			dev_err(&dev->intf->dev,
+				"Couldn't submit HID_REQ_SET_REPORT %d\n",
+				retval);
+		goto unlock_exit;
+	}
+
+	/* send off the urb */
+	usb_fill_int_urb(dev->interrupt_out_urb,
+			 interface_to_usbdev(dev->intf),
+			 usb_sndintpipe(interface_to_usbdev(dev->intf),
+					dev->interrupt_out_endpoint->bEndpointAddress),
+			 dev->interrupt_out_buffer,
+			 bytes_to_write,
+			 ld_usb_interrupt_out_callback,
+			 dev,
+			 dev->interrupt_out_interval);
+
+	dev->interrupt_out_busy = 1;
+	wmb();
+
+	retval = usb_submit_urb(dev->interrupt_out_urb, GFP_KERNEL);
+	if (retval) {
+		dev->interrupt_out_busy = 0;
+		dev_err(&dev->intf->dev,
+			"Couldn't submit interrupt_out_urb %d\n", retval);
+		goto unlock_exit;
+	}
+	retval = bytes_to_write;
+
+unlock_exit:
+	/* unlock the device */
+	mutex_unlock(&dev->mutex);
+
+exit:
+	return retval;
+}
+
+/* file operations needed when we register this driver */
+static const struct file_operations ld_usb_fops = {
+	.owner =	THIS_MODULE,
+	.read  =	ld_usb_read,
+	.write =	ld_usb_write,
+	.open =		ld_usb_open,
+	.release =	ld_usb_release,
+	.poll =		ld_usb_poll,
+};
+
+/*
+ * usb class driver info in order to get a minor number from the usb core,
+ * and to have the device registered with the driver core
+ */
+static struct usb_class_driver ld_usb_class = {
+	.name =		"ldusb%d",
+	.fops =		&ld_usb_fops,
+	.minor_base =	USB_LD_MINOR_BASE,
+};
+
+/*
+ *	ld_usb_probe
+ *
+ *	Called by the usb core when a new device is connected that it thinks
+ *	this driver might be interested in.
+ */
+static int ld_usb_probe(struct usb_interface *intf, const struct usb_device_id *id)
+{
+	struct usb_device *udev = interface_to_usbdev(intf);
+	struct ld_usb *dev = NULL;
+	struct usb_host_interface *iface_desc;
+	char *buffer;
+	int retval = -ENOMEM;
+	int res;
+
+	/* allocate memory for our device state and initialize it */
+
+	dev = kzalloc_obj(*dev);
+	if (!dev)
+		goto exit;
+
+	kref_init(&dev->kref);
+	mutex_init(&dev->mutex);
+	spin_lock_init(&dev->rbsl);
+	dev->intf = intf;
+	init_waitqueue_head(&dev->read_wait);
+	init_waitqueue_head(&dev->write_wait);
+
+	/* workaround for early firmware versions on fast computers */
+	if ((le16_to_cpu(udev->descriptor.idVendor) == USB_VENDOR_ID_LD) &&
+	    ((le16_to_cpu(udev->descriptor.idProduct) == USB_DEVICE_ID_LD_CASSY) ||
+	     (le16_to_cpu(udev->descriptor.idProduct) == USB_DEVICE_ID_LD_COM3LAB)) &&
+	    (le16_to_cpu(udev->descriptor.bcdDevice) <= 0x103)) {
+		buffer = kmalloc(256, GFP_KERNEL);
+		if (!buffer)
+			goto error;
+		/* usb_string makes SETUP+STALL to leave always ControlReadLoop */
+		usb_string(udev, 255, buffer, 256);
+		kfree(buffer);
+	}
+
+	iface_desc = intf->cur_altsetting;
+
+	res = usb_find_last_int_in_endpoint(iface_desc,
+			&dev->interrupt_in_endpoint);
+	if (res) {
+		dev_err(&intf->dev, "Interrupt in endpoint not found\n");
+		retval = res;
+		goto error;
+	}
+
+	res = usb_find_last_int_out_endpoint(iface_desc,
+			&dev->interrupt_out_endpoint);
+	if (res)
+		dev_warn(&intf->dev, "Interrupt out endpoint not found (using control endpoint instead)\n");
+
+	dev->interrupt_in_endpoint_size = usb_endpoint_maxp(dev->interrupt_in_endpoint);
+	dev->ring_buffer = kcalloc(ring_buffer_size,
+			sizeof(size_t) + dev->interrupt_in_endpoint_size,
+			GFP_KERNEL);
+	if (!dev->ring_buffer)
+		goto error;
+	dev->interrupt_in_buffer = kmalloc(dev->interrupt_in_endpoint_size, GFP_KERNEL);
+	if (!dev->interrupt_in_buffer)
+		goto error;
+	dev->interrupt_in_urb = usb_alloc_urb(0, GFP_KERNEL);
+	if (!dev->interrupt_in_urb)
+		goto error;
+	dev->interrupt_out_endpoint_size = dev->interrupt_out_endpoint ? usb_endpoint_maxp(dev->interrupt_out_endpoint) :
+									 udev->descriptor.bMaxPacketSize0;
+	dev->interrupt_out_buffer =
+		kmalloc_array(write_buffer_size,
+			      dev->interrupt_out_endpoint_size, GFP_KERNEL);
+	if (!dev->interrupt_out_buffer)
+		goto error;
+	dev->interrupt_out_urb = usb_alloc_urb(0, GFP_KERNEL);
+	if (!dev->interrupt_out_urb)
+		goto error;
+	dev->interrupt_in_interval = max_t(int, min_interrupt_in_interval,
+					   dev->interrupt_in_endpoint->bInterval);
+	if (dev->interrupt_out_endpoint)
+		dev->interrupt_out_interval = max_t(int, min_interrupt_out_interval,
+						    dev->interrupt_out_endpoint->bInterval);
+
+	/* we can register the device now, as it is ready */
+	usb_set_intfdata(intf, dev);
+
+	retval = usb_register_dev(intf, &ld_usb_class);
+	if (retval) {
+		/* something prevented us from registering this driver */
+		dev_err(&intf->dev, "Not able to get a minor for this device.\n");
+		usb_set_intfdata(intf, NULL);
+		goto error;
+	}
+
+	/* let the user know what node this device is now attached to */
+	dev_info(&intf->dev, "LD USB Device #%d now attached to major %d minor %d\n",
+		(intf->minor - USB_LD_MINOR_BASE), USB_MAJOR, intf->minor);
+
+exit:
+	return retval;
+
+error:
+	kref_put(&dev->kref, ld_usb_delete);
+
+	return retval;
+}
+
+/*
+ *	ld_usb_disconnect
+ *
+ *	Called by the usb core when the device is removed from the system.
+ */
+static void ld_usb_disconnect(struct usb_interface *intf)
+{
+	struct ld_usb *dev;
+	int minor;
+
+	dev = usb_get_intfdata(intf);
+	usb_set_intfdata(intf, NULL);
+
+	minor = intf->minor;
+
+	/* give back our minor */
+	usb_deregister_dev(intf, &ld_usb_class);
+
+	usb_poison_urb(dev->interrupt_in_urb);
+	usb_poison_urb(dev->interrupt_out_urb);
+
+	mutex_lock(&dev->mutex);
+
+	dev->disconnected = 1;
+
+	if (dev->open_count) {
+		/* wake up pollers */
+		wake_up_interruptible_all(&dev->read_wait);
+		wake_up_interruptible_all(&dev->write_wait);
+	}
+
+	mutex_unlock(&dev->mutex);
+
+	kref_put(&dev->kref, ld_usb_delete);
+
+	dev_info(&intf->dev, "LD USB Device #%d now disconnected\n",
+		 (minor - USB_LD_MINOR_BASE));
+}
+
+/* usb specific object needed to register this driver with the usb subsystem */
+static struct usb_driver ld_usb_driver = {
+	.name =		"ldusb",
+	.probe =	ld_usb_probe,
+	.disconnect =	ld_usb_disconnect,
+	.id_table =	ld_usb_table,
+};
+
+module_usb_driver(ld_usb_driver);
+