// 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 250

struct imon {
        struct device *dev;
        struct urb *ir_urb;
        struct rc_dev *rcdev;
        __be64 ir_buf;
        char phys[64];
};

/*
 * The first 5 bytes of data represent IR pulse or space. Each bit, starting
 * from highest bit in the first byte, represents 250µs of data. It is 1
 * for space and 0 for pulse.
 *
 * The station sends 10 packets, and the 7th byte will be number 1 to 10, so
 * when we receive 10 we assume all the data has arrived.
 */
static void imon_ir_data(struct imon *imon)
{
        struct ir_raw_event rawir = {};
        u64 data = be64_to_cpu(imon->ir_buf);
        u8 packet_no = data & 0xff;
        int offset = 40;
        int bit;

        if (packet_no == 0xff)
                return;

        dev_dbg(imon->dev, "data: %*ph", 8, &imon->ir_buf);

        /*
         * Only the first 5 bytes contain IR data. Right shift so we move
         * the IR bits to the lower 40 bits.
         */
        data >>= 24;

        do {
                /*
                 * Find highest set bit which is less or equal to offset
                 *
                 * offset is the bit above (base 0) where we start looking.
                 *
                 * data & (BIT_ULL(offset) - 1) masks off any unwanted bits,
                 * so we have just bits less than offset.
                 *
                 * fls will tell us the highest bit set plus 1 (or 0 if no
                 * bits are set).
                 */
                rawir.pulse = !rawir.pulse;
                bit = fls64(data & (BIT_ULL(offset) - 1));
                if (bit < offset) {
                        dev_dbg(imon->dev, "%s: %d bits",
                                rawir.pulse ? "pulse" : "space", offset - bit);
                        rawir.duration = (offset - bit) * BIT_DURATION;
                        ir_raw_event_store_with_filter(imon->rcdev, &rawir);

                        offset = bit;
                }

                data = ~data;
        } while (offset > 0);

        if (packet_no == 0x0a && !imon->rcdev->idle) {
                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:
                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);