// SPDX-License-Identifier: GPL-2.0+
/*
 * Fast-charge control for Apple "MFi" devices
 *
 * Copyright (C) 2019 Bastien Nocera <hadess@hadess.net>
 */

/* Standard include files */
#include <linux/module.h>
#include <linux/power_supply.h>
#include <linux/slab.h>
#include <linux/usb.h>

MODULE_AUTHOR("Bastien Nocera <hadess@hadess.net>");
MODULE_DESCRIPTION("Fast-charge control for Apple \"MFi\" devices");
MODULE_LICENSE("GPL");

#define TRICKLE_CURRENT_MA              0
#define FAST_CURRENT_MA                 2500

#define APPLE_VENDOR_ID                 0x05ac  /* Apple */

/* The product ID is defined as starting with 0x12nn, as per the
 * "Choosing an Apple Device USB Configuration" section in
 * release R9 (2012) of the "MFi Accessory Hardware Specification"
 *
 * To distinguish an Apple device, a USB host can check the device
 * descriptor of attached USB devices for the following fields:
 * ■ Vendor ID: 0x05AC
 * ■ Product ID: 0x12nn
 *
 * Those checks will be done in .match() and .probe().
 */

static const struct usb_device_id mfi_fc_id_table[] = {
        { .idVendor = APPLE_VENDOR_ID,
          .match_flags = USB_DEVICE_ID_MATCH_VENDOR },
        {},
};

MODULE_DEVICE_TABLE(usb, mfi_fc_id_table);

/* Driver-local specific stuff */
struct mfi_device {
        struct usb_device *udev;
        struct power_supply *battery;
        int charge_type;
};

static int apple_mfi_fc_set_charge_type(struct mfi_device *mfi,
                                        const union power_supply_propval *val)
{
        int current_ma;
        int retval;
        __u8 request_type;

        if (mfi->charge_type == val->intval) {
                dev_dbg(&mfi->udev->dev, "charge type %d already set\n",
                                mfi->charge_type);
                return 0;
        }

        switch (val->intval) {
        case POWER_SUPPLY_CHARGE_TYPE_TRICKLE:
                current_ma = TRICKLE_CURRENT_MA;
                break;
        case POWER_SUPPLY_CHARGE_TYPE_FAST:
                current_ma = FAST_CURRENT_MA;
                break;
        default:
                return -EINVAL;
        }

        request_type = USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE;
        retval = usb_control_msg(mfi->udev, usb_sndctrlpipe(mfi->udev, 0),
                                 0x40, /* Vendor‐defined power request */
                                 request_type,
                                 current_ma, /* wValue, current offset */
                                 current_ma, /* wIndex, current offset */
                                 NULL, 0, USB_CTRL_GET_TIMEOUT);
        if (retval) {
                dev_dbg(&mfi->udev->dev, "retval = %d\n", retval);
                return retval;
        }

        mfi->charge_type = val->intval;

        return 0;
}

static int apple_mfi_fc_get_property(struct power_supply *psy,
                enum power_supply_property psp,
                union power_supply_propval *val)
{
        struct mfi_device *mfi = power_supply_get_drvdata(psy);

        dev_dbg(&mfi->udev->dev, "prop: %d\n", psp);

        switch (psp) {
        case POWER_SUPPLY_PROP_CHARGE_TYPE:
                val->intval = mfi->charge_type;
                break;
        case POWER_SUPPLY_PROP_SCOPE:
                val->intval = POWER_SUPPLY_SCOPE_DEVICE;
                break;
        default:
                return -ENODATA;
        }

        return 0;
}

static int apple_mfi_fc_set_property(struct power_supply *psy,
                enum power_supply_property psp,
                const union power_supply_propval *val)
{
        struct mfi_device *mfi = power_supply_get_drvdata(psy);
        int ret;

        dev_dbg(&mfi->udev->dev, "prop: %d\n", psp);

        ret = pm_runtime_get_sync(&mfi->udev->dev);
        if (ret < 0)
                return ret;

        switch (psp) {
        case POWER_SUPPLY_PROP_CHARGE_TYPE:
                ret = apple_mfi_fc_set_charge_type(mfi, val);
                break;
        default:
                ret = -EINVAL;
        }

        pm_runtime_mark_last_busy(&mfi->udev->dev);
        pm_runtime_put_autosuspend(&mfi->udev->dev);

        return ret;
}

static int apple_mfi_fc_property_is_writeable(struct power_supply *psy,
                                              enum power_supply_property psp)
{
        switch (psp) {
        case POWER_SUPPLY_PROP_CHARGE_TYPE:
                return 1;
        default:
                return 0;
        }
}

static enum power_supply_property apple_mfi_fc_properties[] = {
        POWER_SUPPLY_PROP_CHARGE_TYPE,
        POWER_SUPPLY_PROP_SCOPE
};

static const struct power_supply_desc apple_mfi_fc_desc = {
        .name                   = "apple_mfi_fastcharge",
        .type                   = POWER_SUPPLY_TYPE_BATTERY,
        .properties             = apple_mfi_fc_properties,
        .num_properties         = ARRAY_SIZE(apple_mfi_fc_properties),
        .get_property           = apple_mfi_fc_get_property,
        .set_property           = apple_mfi_fc_set_property,
        .property_is_writeable  = apple_mfi_fc_property_is_writeable
};

static int mfi_fc_probe(struct usb_device *udev)
{
        struct power_supply_config battery_cfg = {};
        struct mfi_device *mfi = NULL;
        int err, idProduct;

        idProduct = le16_to_cpu(udev->descriptor.idProduct);
        /* See comment above mfi_fc_id_table[] */
        if (idProduct < 0x1200 || idProduct > 0x12ff) {
                return -ENODEV;
        }

        mfi = kzalloc(sizeof(struct mfi_device), GFP_KERNEL);
        if (!mfi) {
                err = -ENOMEM;
                goto error;
        }

        battery_cfg.drv_data = mfi;

        mfi->charge_type = POWER_SUPPLY_CHARGE_TYPE_TRICKLE;
        mfi->battery = power_supply_register(&udev->dev,
                                                &apple_mfi_fc_desc,
                                                &battery_cfg);
        if (IS_ERR(mfi->battery)) {
                dev_err(&udev->dev, "Can't register battery\n");
                err = PTR_ERR(mfi->battery);
                goto error;
        }

        mfi->udev = usb_get_dev(udev);
        dev_set_drvdata(&udev->dev, mfi);

        return 0;

error:
        kfree(mfi);
        return err;
}

static void mfi_fc_disconnect(struct usb_device *udev)
{
        struct mfi_device *mfi;

        mfi = dev_get_drvdata(&udev->dev);
        if (mfi->battery)
                power_supply_unregister(mfi->battery);
        dev_set_drvdata(&udev->dev, NULL);
        usb_put_dev(mfi->udev);
        kfree(mfi);
}

static struct usb_device_driver mfi_fc_driver = {
        .name =         "apple-mfi-fastcharge",
        .probe =        mfi_fc_probe,
        .disconnect =   mfi_fc_disconnect,
        .id_table =     mfi_fc_id_table,
        .generic_subclass = 1,
};

static int __init mfi_fc_driver_init(void)
{
        return usb_register_device_driver(&mfi_fc_driver, THIS_MODULE);
}

static void __exit mfi_fc_driver_exit(void)
{
        usb_deregister_device_driver(&mfi_fc_driver);
}

module_init(mfi_fc_driver_init);
module_exit(mfi_fc_driver_exit);