// SPDX-License-Identifier: GPL-2.0+
/*
 * Common/core components for the Surface System Aggregator Module (SSAM) HID
 * transport driver. Provides support for integrated HID devices on Microsoft
 * Surface models.
 *
 * Copyright (C) 2019-2021 Maximilian Luz <luzmaximilian@gmail.com>
 */

#include <linux/unaligned.h>
#include <linux/hid.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/usb/ch9.h>

#include <linux/surface_aggregator/controller.h>

#include "surface_hid_core.h"


/* -- Utility functions. ---------------------------------------------------- */

static bool surface_hid_is_hot_removed(struct surface_hid_device *shid)
{
        /*
         * Non-ssam client devices, i.e. platform client devices, cannot be
         * hot-removed.
         */
        if (!is_ssam_device(shid->dev))
                return false;

        return ssam_device_is_hot_removed(to_ssam_device(shid->dev));
}


/* -- Device descriptor access. --------------------------------------------- */

static int surface_hid_load_hid_descriptor(struct surface_hid_device *shid)
{
        int status;

        if (surface_hid_is_hot_removed(shid))
                return -ENODEV;

        status = shid->ops.get_descriptor(shid, SURFACE_HID_DESC_HID,
                        (u8 *)&shid->hid_desc, sizeof(shid->hid_desc));
        if (status)
                return status;

        if (shid->hid_desc.desc_len != sizeof(shid->hid_desc)) {
                dev_err(shid->dev, "unexpected HID descriptor length: got %u, expected %zu\n",
                        shid->hid_desc.desc_len, sizeof(shid->hid_desc));
                return -EPROTO;
        }

        if (shid->hid_desc.desc_type != HID_DT_HID) {
                dev_err(shid->dev, "unexpected HID descriptor type: got %#04x, expected %#04x\n",
                        shid->hid_desc.desc_type, HID_DT_HID);
                return -EPROTO;
        }

        if (shid->hid_desc.num_descriptors != 1) {
                dev_err(shid->dev, "unexpected number of descriptors: got %u, expected 1\n",
                        shid->hid_desc.num_descriptors);
                return -EPROTO;
        }

        if (shid->hid_desc.report_desc_type != HID_DT_REPORT) {
                dev_err(shid->dev, "unexpected report descriptor type: got %#04x, expected %#04x\n",
                        shid->hid_desc.report_desc_type, HID_DT_REPORT);
                return -EPROTO;
        }

        return 0;
}

static int surface_hid_load_device_attributes(struct surface_hid_device *shid)
{
        int status;

        if (surface_hid_is_hot_removed(shid))
                return -ENODEV;

        status = shid->ops.get_descriptor(shid, SURFACE_HID_DESC_ATTRS,
                        (u8 *)&shid->attrs, sizeof(shid->attrs));
        if (status)
                return status;

        if (get_unaligned_le32(&shid->attrs.length) != sizeof(shid->attrs)) {
                dev_err(shid->dev, "unexpected attribute length: got %u, expected %zu\n",
                        get_unaligned_le32(&shid->attrs.length), sizeof(shid->attrs));
                return -EPROTO;
        }

        return 0;
}


/* -- Transport driver (common). -------------------------------------------- */

static int surface_hid_start(struct hid_device *hid)
{
        struct surface_hid_device *shid = hid->driver_data;

        return ssam_notifier_register(shid->ctrl, &shid->notif);
}

static void surface_hid_stop(struct hid_device *hid)
{
        struct surface_hid_device *shid = hid->driver_data;
        bool hot_removed;

        /*
         * Communication may fail for devices that have been hot-removed. This
         * also includes unregistration of HID events, so we need to check this
         * here. Only if the device has not been marked as hot-removed, we can
         * safely disable events.
         */
        hot_removed = surface_hid_is_hot_removed(shid);

        /* Note: This call will log errors for us, so ignore them here. */
        __ssam_notifier_unregister(shid->ctrl, &shid->notif, !hot_removed);
}

static int surface_hid_open(struct hid_device *hid)
{
        return 0;
}

static void surface_hid_close(struct hid_device *hid)
{
}

static int surface_hid_parse(struct hid_device *hid)
{
        struct surface_hid_device *shid = hid->driver_data;
        size_t len = get_unaligned_le16(&shid->hid_desc.report_desc_len);
        u8 *buf;
        int status;

        if (surface_hid_is_hot_removed(shid))
                return -ENODEV;

        buf = kzalloc(len, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;

        status = shid->ops.get_descriptor(shid, SURFACE_HID_DESC_REPORT, buf, len);
        if (!status)
                status = hid_parse_report(hid, buf, len);

        kfree(buf);
        return status;
}

static int surface_hid_raw_request(struct hid_device *hid, unsigned char reportnum, u8 *buf,
                                   size_t len, unsigned char rtype, int reqtype)
{
        struct surface_hid_device *shid = hid->driver_data;

        if (surface_hid_is_hot_removed(shid))
                return -ENODEV;

        if (rtype == HID_OUTPUT_REPORT && reqtype == HID_REQ_SET_REPORT)
                return shid->ops.output_report(shid, reportnum, buf, len);

        else if (rtype == HID_FEATURE_REPORT && reqtype == HID_REQ_GET_REPORT)
                return shid->ops.get_feature_report(shid, reportnum, buf, len);

        else if (rtype == HID_FEATURE_REPORT && reqtype == HID_REQ_SET_REPORT)
                return shid->ops.set_feature_report(shid, reportnum, buf, len);

        return -EIO;
}

static const struct hid_ll_driver surface_hid_ll_driver = {
        .start       = surface_hid_start,
        .stop        = surface_hid_stop,
        .open        = surface_hid_open,
        .close       = surface_hid_close,
        .parse       = surface_hid_parse,
        .raw_request = surface_hid_raw_request,
};


/* -- Common device setup. -------------------------------------------------- */

int surface_hid_device_add(struct surface_hid_device *shid)
{
        int status;

        status = surface_hid_load_hid_descriptor(shid);
        if (status)
                return status;

        status = surface_hid_load_device_attributes(shid);
        if (status)
                return status;

        shid->hid = hid_allocate_device();
        if (IS_ERR(shid->hid))
                return PTR_ERR(shid->hid);

        shid->hid->dev.parent = shid->dev;
        shid->hid->bus = BUS_HOST;
        shid->hid->vendor = get_unaligned_le16(&shid->attrs.vendor);
        shid->hid->product = get_unaligned_le16(&shid->attrs.product);
        shid->hid->version = get_unaligned_le16(&shid->hid_desc.hid_version);
        shid->hid->country = shid->hid_desc.country_code;

        snprintf(shid->hid->name, sizeof(shid->hid->name), "Microsoft Surface %04X:%04X",
                 shid->hid->vendor, shid->hid->product);

        strscpy(shid->hid->phys, dev_name(shid->dev), sizeof(shid->hid->phys));

        shid->hid->driver_data = shid;
        shid->hid->ll_driver = &surface_hid_ll_driver;

        status = hid_add_device(shid->hid);
        if (status)
                hid_destroy_device(shid->hid);

        return status;
}
EXPORT_SYMBOL_GPL(surface_hid_device_add);

void surface_hid_device_destroy(struct surface_hid_device *shid)
{
        hid_destroy_device(shid->hid);
}
EXPORT_SYMBOL_GPL(surface_hid_device_destroy);


/* -- PM ops. --------------------------------------------------------------- */

#ifdef CONFIG_PM_SLEEP

static int surface_hid_suspend(struct device *dev)
{
        struct surface_hid_device *d = dev_get_drvdata(dev);

        return hid_driver_suspend(d->hid, PMSG_SUSPEND);
}

static int surface_hid_resume(struct device *dev)
{
        struct surface_hid_device *d = dev_get_drvdata(dev);

        return hid_driver_resume(d->hid);
}

static int surface_hid_freeze(struct device *dev)
{
        struct surface_hid_device *d = dev_get_drvdata(dev);

        return hid_driver_suspend(d->hid, PMSG_FREEZE);
}

static int surface_hid_poweroff(struct device *dev)
{
        struct surface_hid_device *d = dev_get_drvdata(dev);

        return hid_driver_suspend(d->hid, PMSG_HIBERNATE);
}

static int surface_hid_restore(struct device *dev)
{
        struct surface_hid_device *d = dev_get_drvdata(dev);

        return hid_driver_reset_resume(d->hid);
}

const struct dev_pm_ops surface_hid_pm_ops = {
        .freeze   = surface_hid_freeze,
        .thaw     = surface_hid_resume,
        .suspend  = surface_hid_suspend,
        .resume   = surface_hid_resume,
        .poweroff = surface_hid_poweroff,
        .restore  = surface_hid_restore,
};
EXPORT_SYMBOL_GPL(surface_hid_pm_ops);

#else /* CONFIG_PM_SLEEP */

const struct dev_pm_ops surface_hid_pm_ops = { };
EXPORT_SYMBOL_GPL(surface_hid_pm_ops);

#endif /* CONFIG_PM_SLEEP */

MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
MODULE_DESCRIPTION("HID transport driver core for Surface System Aggregator Module");
MODULE_LICENSE("GPL");