// SPDX-License-Identifier: GPL-2.0
/*
 * Generic USB GNSS receiver driver
 *
 * Copyright (C) 2021 Johan Hovold <johan@kernel.org>
 */

#include <linux/errno.h>
#include <linux/gnss.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/usb.h>

#define GNSS_USB_READ_BUF_LEN   512
#define GNSS_USB_WRITE_TIMEOUT  1000

static const struct usb_device_id gnss_usb_id_table[] = {
        { USB_DEVICE(0x1199, 0xb000) },         /* Sierra Wireless XM1210 */
        { }
};
MODULE_DEVICE_TABLE(usb, gnss_usb_id_table);

struct gnss_usb {
        struct usb_device *udev;
        struct usb_interface *intf;
        struct gnss_device *gdev;
        struct urb *read_urb;
        unsigned int write_pipe;
};

static void gnss_usb_rx_complete(struct urb *urb)
{
        struct gnss_usb *gusb = urb->context;
        struct gnss_device *gdev = gusb->gdev;
        int status = urb->status;
        int len;
        int ret;

        switch (status) {
        case 0:
                break;
        case -ENOENT:
        case -ECONNRESET:
        case -ESHUTDOWN:
                dev_dbg(&gdev->dev, "urb stopped: %d\n", status);
                return;
        case -EPIPE:
                dev_err(&gdev->dev, "urb stopped: %d\n", status);
                return;
        default:
                dev_dbg(&gdev->dev, "nonzero urb status: %d\n", status);
                goto resubmit;
        }

        len = urb->actual_length;
        if (len == 0)
                goto resubmit;

        ret = gnss_insert_raw(gdev, urb->transfer_buffer, len);
        if (ret < len)
                dev_dbg(&gdev->dev, "dropped %d bytes\n", len - ret);
resubmit:
        ret = usb_submit_urb(urb, GFP_ATOMIC);
        if (ret && ret != -EPERM && ret != -ENODEV)
                dev_err(&gdev->dev, "failed to resubmit urb: %d\n", ret);
}

static int gnss_usb_open(struct gnss_device *gdev)
{
        struct gnss_usb *gusb = gnss_get_drvdata(gdev);
        int ret;

        ret = usb_submit_urb(gusb->read_urb, GFP_KERNEL);
        if (ret) {
                if (ret != -EPERM && ret != -ENODEV)
                        dev_err(&gdev->dev, "failed to submit urb: %d\n", ret);
                return ret;
        }

        return 0;
}

static void gnss_usb_close(struct gnss_device *gdev)
{
        struct gnss_usb *gusb = gnss_get_drvdata(gdev);

        usb_kill_urb(gusb->read_urb);
}

static int gnss_usb_write_raw(struct gnss_device *gdev,
                const unsigned char *buf, size_t count)
{
        struct gnss_usb *gusb = gnss_get_drvdata(gdev);
        void *tbuf;
        int ret;

        tbuf = kmemdup(buf, count, GFP_KERNEL);
        if (!tbuf)
                return -ENOMEM;

        ret = usb_bulk_msg(gusb->udev, gusb->write_pipe, tbuf, count, NULL,
                        GNSS_USB_WRITE_TIMEOUT);
        kfree(tbuf);
        if (ret)
                return ret;

        return count;
}

static const struct gnss_operations gnss_usb_gnss_ops = {
        .open           = gnss_usb_open,
        .close          = gnss_usb_close,
        .write_raw      = gnss_usb_write_raw,
};

static int gnss_usb_probe(struct usb_interface *intf, const struct usb_device_id *id)
{
        struct usb_device *udev = interface_to_usbdev(intf);
        struct usb_endpoint_descriptor *in, *out;
        struct gnss_device *gdev;
        struct gnss_usb *gusb;
        struct urb *urb;
        size_t buf_len;
        void *buf;
        int ret;

        ret = usb_find_common_endpoints(intf->cur_altsetting, &in, &out, NULL,
                        NULL);
        if (ret)
                return ret;

        gusb = kzalloc_obj(*gusb);
        if (!gusb)
                return -ENOMEM;

        gdev = gnss_allocate_device(&intf->dev);
        if (!gdev) {
                ret = -ENOMEM;
                goto err_free_gusb;
        }

        gdev->ops = &gnss_usb_gnss_ops;
        gdev->type = GNSS_TYPE_NMEA;
        gnss_set_drvdata(gdev, gusb);

        urb = usb_alloc_urb(0, GFP_KERNEL);
        if (!urb) {
                ret = -ENOMEM;
                goto err_put_gdev;
        }

        buf_len = max(usb_endpoint_maxp(in), GNSS_USB_READ_BUF_LEN);

        buf = kzalloc(buf_len, GFP_KERNEL);
        if (!buf) {
                ret = -ENOMEM;
                goto err_free_urb;
        }

        usb_fill_bulk_urb(urb, udev,
                        usb_rcvbulkpipe(udev, usb_endpoint_num(in)),
                        buf, buf_len, gnss_usb_rx_complete, gusb);

        gusb->intf = intf;
        gusb->udev = udev;
        gusb->gdev = gdev;
        gusb->read_urb = urb;
        gusb->write_pipe = usb_sndbulkpipe(udev, usb_endpoint_num(out));

        ret = gnss_register_device(gdev);
        if (ret)
                goto err_free_buf;

        usb_set_intfdata(intf, gusb);

        return 0;

err_free_buf:
        kfree(buf);
err_free_urb:
        usb_free_urb(urb);
err_put_gdev:
        gnss_put_device(gdev);
err_free_gusb:
        kfree(gusb);

        return ret;
}

static void gnss_usb_disconnect(struct usb_interface *intf)
{
        struct gnss_usb *gusb = usb_get_intfdata(intf);

        gnss_deregister_device(gusb->gdev);

        kfree(gusb->read_urb->transfer_buffer);
        usb_free_urb(gusb->read_urb);
        gnss_put_device(gusb->gdev);
        kfree(gusb);
}

static struct usb_driver gnss_usb_driver = {
        .name           = "gnss-usb",
        .probe          = gnss_usb_probe,
        .disconnect     = gnss_usb_disconnect,
        .id_table       = gnss_usb_id_table,
};
module_usb_driver(gnss_usb_driver);

MODULE_AUTHOR("Johan Hovold <johan@kernel.org>");
MODULE_DESCRIPTION("Generic USB GNSS receiver driver");
MODULE_LICENSE("GPL v2");