--- /dev/null
+// SPDX-License-Identifier: GPL-2.0+
+//
+// Copyright (C) 2018 Sean Young <sean@mess.org>
+
+#include <linux/module.h>
+#include <linux/usb.h>
+#include <linux/usb/input.h>
+#include <media/rc-core.h>
+
+/* Each bit is 250us */
+#define BIT_DURATION 250000
+
+struct imon {
+       struct device *dev;
+       struct urb *ir_urb;
+       struct rc_dev *rcdev;
+       u8 ir_buf[8];
+       char phys[64];
+};
+
+/*
+ * ffs/find_next_bit() searches in the wrong direction, so open-code our own.
+ */
+static inline int is_bit_set(const u8 *buf, int bit)
+{
+       return buf[bit / 8] & (0x80 >> (bit & 7));
+}
+
+static void imon_ir_data(struct imon *imon)
+{
+       DEFINE_IR_RAW_EVENT(rawir);
+       int offset = 0, size = 5 * 8;
+       int bit;
+
+       dev_dbg(imon->dev, "data: %*ph", 8, imon->ir_buf);
+
+       while (offset < size) {
+               bit = offset;
+               while (!is_bit_set(imon->ir_buf, bit) && bit < size)
+                       bit++;
+               dev_dbg(imon->dev, "pulse: %d bits", bit - offset);
+               if (bit > offset) {
+                       rawir.pulse = true;
+                       rawir.duration = (bit - offset) * BIT_DURATION;
+                       ir_raw_event_store_with_filter(imon->rcdev, &rawir);
+               }
+
+               if (bit >= size)
+                       break;
+
+               offset = bit;
+               while (is_bit_set(imon->ir_buf, bit) && bit < size)
+                       bit++;
+               dev_dbg(imon->dev, "space: %d bits", bit - offset);
+
+               rawir.pulse = false;
+               rawir.duration = (bit - offset) * BIT_DURATION;
+               ir_raw_event_store_with_filter(imon->rcdev, &rawir);
+
+               offset = bit;
+       }
+
+       if (imon->ir_buf[7] == 0x0a) {
+               ir_raw_event_set_idle(imon->rcdev, true);
+               ir_raw_event_handle(imon->rcdev);
+       }
+}
+
+static void imon_ir_rx(struct urb *urb)
+{
+       struct imon *imon = urb->context;
+       int ret;
+
+       switch (urb->status) {
+       case 0:
+               if (imon->ir_buf[7] != 0xff)
+                       imon_ir_data(imon);
+               break;
+       case -ECONNRESET:
+       case -ENOENT:
+       case -ESHUTDOWN:
+               usb_unlink_urb(urb);
+               return;
+       case -EPIPE:
+       default:
+               dev_dbg(imon->dev, "error: urb status = %d", urb->status);
+               break;
+       }
+
+       ret = usb_submit_urb(urb, GFP_ATOMIC);
+       if (ret && ret != -ENODEV)
+               dev_warn(imon->dev, "failed to resubmit urb: %d", ret);
+}
+
+static int imon_probe(struct usb_interface *intf,
+                     const struct usb_device_id *id)
+{
+       struct usb_endpoint_descriptor *ir_ep = NULL;
+       struct usb_host_interface *idesc;
+       struct usb_device *udev;
+       struct rc_dev *rcdev;
+       struct imon *imon;
+       int i, ret;
+
+       udev = interface_to_usbdev(intf);
+       idesc = intf->cur_altsetting;
+
+       for (i = 0; i < idesc->desc.bNumEndpoints; i++) {
+               struct usb_endpoint_descriptor *ep = &idesc->endpoint[i].desc;
+
+               if (usb_endpoint_is_int_in(ep)) {
+                       ir_ep = ep;
+                       break;
+               }
+       }
+
+       if (!ir_ep) {
+               dev_err(&intf->dev, "IR endpoint missing");
+               return -ENODEV;
+       }
+
+       imon = devm_kmalloc(&intf->dev, sizeof(*imon), GFP_KERNEL);
+       if (!imon)
+               return -ENOMEM;
+
+       imon->ir_urb = usb_alloc_urb(0, GFP_KERNEL);
+       if (!imon->ir_urb)
+               return -ENOMEM;
+
+       imon->dev = &intf->dev;
+       usb_fill_int_urb(imon->ir_urb, udev,
+                        usb_rcvintpipe(udev, ir_ep->bEndpointAddress),
+                        imon->ir_buf, sizeof(imon->ir_buf),
+                        imon_ir_rx, imon, ir_ep->bInterval);
+
+       rcdev = devm_rc_allocate_device(&intf->dev, RC_DRIVER_IR_RAW);
+       if (!rcdev) {
+               ret = -ENOMEM;
+               goto free_urb;
+       }
+
+       usb_make_path(udev, imon->phys, sizeof(imon->phys));
+
+       rcdev->device_name = "iMON Station";
+       rcdev->driver_name = KBUILD_MODNAME;
+       rcdev->input_phys = imon->phys;
+       usb_to_input_id(udev, &rcdev->input_id);
+       rcdev->dev.parent = &intf->dev;
+       rcdev->allowed_protocols = RC_PROTO_BIT_ALL_IR_DECODER;
+       rcdev->map_name = RC_MAP_IMON_RSC;
+       rcdev->rx_resolution = BIT_DURATION;
+       rcdev->priv = imon;
+
+       ret = devm_rc_register_device(&intf->dev, rcdev);
+       if (ret)
+               goto free_urb;
+
+       imon->rcdev = rcdev;
+
+       ret = usb_submit_urb(imon->ir_urb, GFP_KERNEL);
+       if (ret)
+               goto free_urb;
+
+       usb_set_intfdata(intf, imon);
+
+       return 0;
+
+free_urb:
+       usb_free_urb(imon->ir_urb);
+       return ret;
+}
+
+static void imon_disconnect(struct usb_interface *intf)
+{
+       struct imon *imon = usb_get_intfdata(intf);
+
+       usb_kill_urb(imon->ir_urb);
+       usb_free_urb(imon->ir_urb);
+}
+
+static const struct usb_device_id imon_table[] = {
+       /* SoundGraph iMON (IR only) -- sg_imon.inf */
+       { USB_DEVICE(0x04e8, 0xff30) },
+       {}
+};
+
+static struct usb_driver imon_driver = {
+       .name = KBUILD_MODNAME,
+       .probe = imon_probe,
+       .disconnect = imon_disconnect,
+       .id_table = imon_table
+};
+
+module_usb_driver(imon_driver);
+
+MODULE_DESCRIPTION("Early raw iMON IR devices");
+MODULE_AUTHOR("Sean Young <sean@mess.org>");
+MODULE_LICENSE("GPL");
+MODULE_DEVICE_TABLE(usb, imon_table);