// SPDX-License-Identifier: GPL-2.0-only
/*
 *  Copyright (c) 2013, Microsoft Corporation.
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/completion.h>
#include <linux/hyperv.h>
#include <linux/serio.h>
#include <linux/slab.h>

/*
 * Current version 1.0
 *
 */
#define SYNTH_KBD_VERSION_MAJOR 1
#define SYNTH_KBD_VERSION_MINOR 0
#define SYNTH_KBD_VERSION               (SYNTH_KBD_VERSION_MINOR | \
                                         (SYNTH_KBD_VERSION_MAJOR << 16))


/*
 * Message types in the synthetic input protocol
 */
enum synth_kbd_msg_type {
        SYNTH_KBD_PROTOCOL_REQUEST = 1,
        SYNTH_KBD_PROTOCOL_RESPONSE = 2,
        SYNTH_KBD_EVENT = 3,
        SYNTH_KBD_LED_INDICATORS = 4,
};

/*
 * Basic message structures.
 */
struct synth_kbd_msg_hdr {
        __le32 type;
};

struct synth_kbd_msg {
        struct synth_kbd_msg_hdr header;
        char data[]; /* Enclosed message */
};

union synth_kbd_version {
        __le32 version;
};

/*
 * Protocol messages
 */
struct synth_kbd_protocol_request {
        struct synth_kbd_msg_hdr header;
        union synth_kbd_version version_requested;
};

#define PROTOCOL_ACCEPTED       BIT(0)
struct synth_kbd_protocol_response {
        struct synth_kbd_msg_hdr header;
        __le32 proto_status;
};

#define IS_UNICODE      BIT(0)
#define IS_BREAK        BIT(1)
#define IS_E0           BIT(2)
#define IS_E1           BIT(3)
struct synth_kbd_keystroke {
        struct synth_kbd_msg_hdr header;
        __le16 make_code;
        __le16 reserved0;
        __le32 info; /* Additional information */
};


#define HK_MAXIMUM_MESSAGE_SIZE 256

#define KBD_VSC_SEND_RING_BUFFER_SIZE   VMBUS_RING_SIZE(36 * 1024)
#define KBD_VSC_RECV_RING_BUFFER_SIZE   VMBUS_RING_SIZE(36 * 1024)

#define XTKBD_EMUL0     0xe0
#define XTKBD_EMUL1     0xe1
#define XTKBD_RELEASE   0x80


/*
 * Represents a keyboard device
 */
struct hv_kbd_dev {
        struct hv_device *hv_dev;
        struct serio *hv_serio;
        struct synth_kbd_protocol_request protocol_req;
        struct synth_kbd_protocol_response protocol_resp;
        /* Synchronize the request/response if needed */
        struct completion wait_event;
        spinlock_t lock; /* protects 'started' field */
        bool started;
};

static void hv_kbd_on_receive(struct hv_device *hv_dev,
                              struct synth_kbd_msg *msg, u32 msg_length)
{
        struct hv_kbd_dev *kbd_dev = hv_get_drvdata(hv_dev);
        struct synth_kbd_keystroke *ks_msg;
        u32 msg_type = __le32_to_cpu(msg->header.type);
        u32 info;
        u16 scan_code;

        switch (msg_type) {
        case SYNTH_KBD_PROTOCOL_RESPONSE:
                /*
                 * Validate the information provided by the host.
                 * If the host is giving us a bogus packet,
                 * drop the packet (hoping the problem
                 * goes away).
                 */
                if (msg_length < sizeof(struct synth_kbd_protocol_response)) {
                        dev_err(&hv_dev->device,
                                "Illegal protocol response packet (len: %d)\n",
                                msg_length);
                        break;
                }

                memcpy(&kbd_dev->protocol_resp, msg,
                        sizeof(struct synth_kbd_protocol_response));
                complete(&kbd_dev->wait_event);
                break;

        case SYNTH_KBD_EVENT:
                /*
                 * Validate the information provided by the host.
                 * If the host is giving us a bogus packet,
                 * drop the packet (hoping the problem
                 * goes away).
                 */
                if (msg_length < sizeof(struct  synth_kbd_keystroke)) {
                        dev_err(&hv_dev->device,
                                "Illegal keyboard event packet (len: %d)\n",
                                msg_length);
                        break;
                }

                ks_msg = (struct synth_kbd_keystroke *)msg;
                info = __le32_to_cpu(ks_msg->info);

                /*
                 * Inject the information through the serio interrupt.
                 */
                scoped_guard(spinlock_irqsave, &kbd_dev->lock) {
                        if (kbd_dev->started) {
                                if (info & IS_E0)
                                        serio_interrupt(kbd_dev->hv_serio,
                                                        XTKBD_EMUL0, 0);
                                if (info & IS_E1)
                                        serio_interrupt(kbd_dev->hv_serio,
                                                        XTKBD_EMUL1, 0);
                                scan_code = __le16_to_cpu(ks_msg->make_code);
                                if (info & IS_BREAK)
                                        scan_code |= XTKBD_RELEASE;

                                serio_interrupt(kbd_dev->hv_serio,
                                                scan_code, 0);
                        }
                }

                /*
                 * Only trigger a wakeup on key down, otherwise
                 * "echo freeze > /sys/power/state" can't really enter the
                 * state because the Enter-UP can trigger a wakeup at once.
                 */
                if (!(info & IS_BREAK))
                        pm_wakeup_hard_event(&hv_dev->device);

                break;

        default:
                dev_err(&hv_dev->device,
                        "unhandled message type %d\n", msg_type);
        }
}

static void hv_kbd_handle_received_packet(struct hv_device *hv_dev,
                                          struct vmpacket_descriptor *desc,
                                          u32 bytes_recvd,
                                          u64 req_id)
{
        struct synth_kbd_msg *msg;
        u32 msg_sz;

        switch (desc->type) {
        case VM_PKT_COMP:
                break;

        case VM_PKT_DATA_INBAND:
                /*
                 * We have a packet that has "inband" data. The API used
                 * for retrieving the packet guarantees that the complete
                 * packet is read. So, minimally, we should be able to
                 * parse the payload header safely (assuming that the host
                 * can be trusted.  Trusting the host seems to be a
                 * reasonable assumption because in a virtualized
                 * environment there is not whole lot you can do if you
                 * don't trust the host.
                 *
                 * Nonetheless, let us validate if the host can be trusted
                 * (in a trivial way).  The interesting aspect of this
                 * validation is how do you recover if we discover that the
                 * host is not to be trusted? Simply dropping the packet, I
                 * don't think is an appropriate recovery.  In the interest
                 * of failing fast, it may be better to crash the guest.
                 * For now, I will just drop the packet!
                 */

                msg_sz = bytes_recvd - (desc->offset8 << 3);
                if (msg_sz <= sizeof(struct synth_kbd_msg_hdr)) {
                        /*
                         * Drop the packet and hope
                         * the problem magically goes away.
                         */
                        dev_err(&hv_dev->device,
                                "Illegal packet (type: %d, tid: %llx, size: %d)\n",
                                desc->type, req_id, msg_sz);
                        break;
                }

                msg = (void *)desc + (desc->offset8 << 3);
                hv_kbd_on_receive(hv_dev, msg, msg_sz);
                break;

        default:
                dev_err(&hv_dev->device,
                        "unhandled packet type %d, tid %llx len %d\n",
                        desc->type, req_id, bytes_recvd);
                break;
        }
}

static void hv_kbd_on_channel_callback(void *context)
{
        struct vmpacket_descriptor *desc;
        struct hv_device *hv_dev = context;
        u32 bytes_recvd;
        u64 req_id;

        foreach_vmbus_pkt(desc, hv_dev->channel) {
                bytes_recvd = desc->len8 * 8;
                req_id = desc->trans_id;

                hv_kbd_handle_received_packet(hv_dev, desc, bytes_recvd,
                                              req_id);
        }
}

static int hv_kbd_connect_to_vsp(struct hv_device *hv_dev)
{
        struct hv_kbd_dev *kbd_dev = hv_get_drvdata(hv_dev);
        struct synth_kbd_protocol_request *request;
        struct synth_kbd_protocol_response *response;
        u32 proto_status;
        int error;

        reinit_completion(&kbd_dev->wait_event);

        request = &kbd_dev->protocol_req;
        memset(request, 0, sizeof(struct synth_kbd_protocol_request));
        request->header.type = __cpu_to_le32(SYNTH_KBD_PROTOCOL_REQUEST);
        request->version_requested.version = __cpu_to_le32(SYNTH_KBD_VERSION);

        error = vmbus_sendpacket(hv_dev->channel, request,
                                 sizeof(struct synth_kbd_protocol_request),
                                 (unsigned long)request,
                                 VM_PKT_DATA_INBAND,
                                 VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
        if (error)
                return error;

        if (!wait_for_completion_timeout(&kbd_dev->wait_event, 10 * HZ))
                return -ETIMEDOUT;

        response = &kbd_dev->protocol_resp;
        proto_status = __le32_to_cpu(response->proto_status);
        if (!(proto_status & PROTOCOL_ACCEPTED)) {
                dev_err(&hv_dev->device,
                        "synth_kbd protocol request failed (version %d)\n",
                        SYNTH_KBD_VERSION);
                return -ENODEV;
        }

        return 0;
}

static int hv_kbd_start(struct serio *serio)
{
        struct hv_kbd_dev *kbd_dev = serio->port_data;

        guard(spinlock_irqsave)(&kbd_dev->lock);

        kbd_dev->started = true;

        return 0;
}

static void hv_kbd_stop(struct serio *serio)
{
        struct hv_kbd_dev *kbd_dev = serio->port_data;

        guard(spinlock_irqsave)(&kbd_dev->lock);

        kbd_dev->started = false;
}

static int hv_kbd_probe(struct hv_device *hv_dev,
                        const struct hv_vmbus_device_id *dev_id)
{
        struct hv_kbd_dev *kbd_dev;
        struct serio *hv_serio;
        int error;

        kbd_dev = kzalloc_obj(*kbd_dev);
        hv_serio = kzalloc_obj(*hv_serio);
        if (!kbd_dev || !hv_serio) {
                error = -ENOMEM;
                goto err_free_mem;
        }

        kbd_dev->hv_dev = hv_dev;
        kbd_dev->hv_serio = hv_serio;
        spin_lock_init(&kbd_dev->lock);
        init_completion(&kbd_dev->wait_event);
        hv_set_drvdata(hv_dev, kbd_dev);

        hv_serio->dev.parent  = &hv_dev->device;
        hv_serio->id.type = SERIO_8042_XL;
        hv_serio->port_data = kbd_dev;
        strscpy(hv_serio->name, dev_name(&hv_dev->device),
                sizeof(hv_serio->name));
        strscpy(hv_serio->phys, dev_name(&hv_dev->device),
                sizeof(hv_serio->phys));

        hv_serio->start = hv_kbd_start;
        hv_serio->stop = hv_kbd_stop;

        error = vmbus_open(hv_dev->channel,
                           KBD_VSC_SEND_RING_BUFFER_SIZE,
                           KBD_VSC_RECV_RING_BUFFER_SIZE,
                           NULL, 0,
                           hv_kbd_on_channel_callback,
                           hv_dev);
        if (error)
                goto err_free_mem;

        error = hv_kbd_connect_to_vsp(hv_dev);
        if (error)
                goto err_close_vmbus;

        serio_register_port(kbd_dev->hv_serio);

        device_init_wakeup(&hv_dev->device, true);

        return 0;

err_close_vmbus:
        vmbus_close(hv_dev->channel);
err_free_mem:
        kfree(hv_serio);
        kfree(kbd_dev);
        return error;
}

static void hv_kbd_remove(struct hv_device *hv_dev)
{
        struct hv_kbd_dev *kbd_dev = hv_get_drvdata(hv_dev);

        serio_unregister_port(kbd_dev->hv_serio);
        vmbus_close(hv_dev->channel);
        kfree(kbd_dev);

        hv_set_drvdata(hv_dev, NULL);
}

static int hv_kbd_suspend(struct hv_device *hv_dev)
{
        vmbus_close(hv_dev->channel);

        return 0;
}

static int hv_kbd_resume(struct hv_device *hv_dev)
{
        int ret;

        ret = vmbus_open(hv_dev->channel,
                         KBD_VSC_SEND_RING_BUFFER_SIZE,
                         KBD_VSC_RECV_RING_BUFFER_SIZE,
                         NULL, 0,
                         hv_kbd_on_channel_callback,
                         hv_dev);
        if (ret == 0)
                ret = hv_kbd_connect_to_vsp(hv_dev);

        return ret;
}

static const struct hv_vmbus_device_id id_table[] = {
        /* Keyboard guid */
        { HV_KBD_GUID, },
        { },
};

MODULE_DEVICE_TABLE(vmbus, id_table);

static struct  hv_driver hv_kbd_drv = {
        .name = KBUILD_MODNAME,
        .id_table = id_table,
        .probe = hv_kbd_probe,
        .remove = hv_kbd_remove,
        .suspend = hv_kbd_suspend,
        .resume = hv_kbd_resume,
        .driver = {
                .probe_type = PROBE_PREFER_ASYNCHRONOUS,
        },
};

static int __init hv_kbd_init(void)
{
        return vmbus_driver_register(&hv_kbd_drv);
}

static void __exit hv_kbd_exit(void)
{
        vmbus_driver_unregister(&hv_kbd_drv);
}

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Microsoft Hyper-V Synthetic Keyboard Driver");

module_init(hv_kbd_init);
module_exit(hv_kbd_exit);