// SPDX-License-Identifier: GPL-2.0-only
/*
 *  WMI methods for use with dell-smbios
 *
 *  Copyright (c) 2017 Dell Inc.
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/device.h>
#include <linux/dmi.h>
#include <linux/fs.h>
#include <linux/list.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/uaccess.h>
#include <linux/wmi.h>
#include <uapi/linux/wmi.h>
#include "dell-smbios.h"
#include "dell-wmi-descriptor.h"

static DEFINE_MUTEX(call_mutex);
static DEFINE_MUTEX(list_mutex);
static int wmi_supported;

struct misc_bios_flags_structure {
        struct dmi_header header;
        u16 flags0;
} __packed;
#define FLAG_HAS_ACPI_WMI 0x02

#define DELL_WMI_SMBIOS_GUID "A80593CE-A997-11DA-B012-B622A1EF5492"

struct wmi_smbios_priv {
        struct dell_wmi_smbios_buffer *buf;
        struct list_head list;
        struct wmi_device *wdev;
        struct device *child;
        u64 req_buf_size;
        struct miscdevice char_dev;
};
static LIST_HEAD(wmi_list);

static inline struct wmi_smbios_priv *get_first_smbios_priv(void)
{
        return list_first_entry_or_null(&wmi_list,
                                        struct wmi_smbios_priv,
                                        list);
}

static int run_smbios_call(struct wmi_device *wdev)
{
        struct wmi_smbios_priv *priv = dev_get_drvdata(&wdev->dev);
        const struct wmi_buffer input = {
                .length = priv->req_buf_size - sizeof(u64),
                .data = &priv->buf->std,
        };
        struct wmi_buffer output;
        int ret;

        dev_dbg(&wdev->dev, "evaluating: %u/%u [%x,%x,%x,%x]\n",
                priv->buf->std.cmd_class, priv->buf->std.cmd_select,
                priv->buf->std.input[0], priv->buf->std.input[1],
                priv->buf->std.input[2], priv->buf->std.input[3]);

        /*
         * The output buffer returned by the WMI method should have at least the size
         * of the input buffer.
         */
        ret = wmidev_invoke_method(wdev, 0, 1, &input, &output, input.length);
        if (ret < 0)
                return ret;

        memcpy(input.data, output.data, input.length);
        kfree(output.data);
        dev_dbg(&wdev->dev, "result: [%08x,%08x,%08x,%08x]\n",
                priv->buf->std.output[0], priv->buf->std.output[1],
                priv->buf->std.output[2], priv->buf->std.output[3]);

        return 0;
}

static int dell_smbios_wmi_call(struct calling_interface_buffer *buffer)
{
        struct wmi_smbios_priv *priv;
        size_t difference;
        size_t size;
        int ret;

        mutex_lock(&call_mutex);
        priv = get_first_smbios_priv();
        if (!priv) {
                ret = -ENODEV;
                goto out_wmi_call;
        }

        size = sizeof(struct calling_interface_buffer);
        difference = priv->req_buf_size - sizeof(u64) - size;

        memset(&priv->buf->ext, 0, difference);
        memcpy(&priv->buf->std, buffer, size);
        ret = run_smbios_call(priv->wdev);
        memcpy(buffer, &priv->buf->std, size);
out_wmi_call:
        mutex_unlock(&call_mutex);

        return ret;
}

static int dell_smbios_wmi_open(struct inode *inode, struct file *filp)
{
        struct wmi_smbios_priv *priv;

        priv = container_of(filp->private_data, struct wmi_smbios_priv, char_dev);
        filp->private_data = priv;

        return nonseekable_open(inode, filp);
}

static ssize_t dell_smbios_wmi_read(struct file *filp, char __user *buffer, size_t length,
                                    loff_t *offset)
{
        struct wmi_smbios_priv *priv = filp->private_data;

        return simple_read_from_buffer(buffer, length, offset, &priv->req_buf_size,
                                       sizeof(priv->req_buf_size));
}

static long dell_smbios_wmi_do_ioctl(struct wmi_smbios_priv *priv,
                                     struct dell_wmi_smbios_buffer __user *arg)
{
        long ret;

        if (get_user(priv->buf->length, &arg->length))
                return -EFAULT;

        if (priv->buf->length < priv->req_buf_size)
                return -EINVAL;

        /* if it's too big, warn, driver will only use what is needed */
        if (priv->buf->length > priv->req_buf_size)
                dev_err(&priv->wdev->dev, "Buffer %llu is bigger than required %llu\n",
                        priv->buf->length, priv->req_buf_size);

        if (copy_from_user(priv->buf, arg, priv->req_buf_size))
                return -EFAULT;

        if (dell_smbios_call_filter(&priv->wdev->dev, &priv->buf->std)) {
                dev_err(&priv->wdev->dev, "Invalid call %d/%d:%8x\n",
                        priv->buf->std.cmd_class,
                        priv->buf->std.cmd_select,
                        priv->buf->std.input[0]);

                return -EINVAL;
        }

        ret = run_smbios_call(priv->wdev);
        if (ret)
                return ret;

        if (copy_to_user(arg, priv->buf, priv->req_buf_size))
                return -EFAULT;

        return 0;
}

static long dell_smbios_wmi_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
        struct dell_wmi_smbios_buffer __user *input = (struct dell_wmi_smbios_buffer __user *)arg;
        struct wmi_smbios_priv *priv = filp->private_data;
        long ret;

        if (cmd != DELL_WMI_SMBIOS_CMD)
                return -ENOIOCTLCMD;

        mutex_lock(&call_mutex);
        ret = dell_smbios_wmi_do_ioctl(priv, input);
        mutex_unlock(&call_mutex);

        return ret;
}

static const struct file_operations dell_smbios_wmi_fops = {
        .owner          = THIS_MODULE,
        .open           = dell_smbios_wmi_open,
        .read           = dell_smbios_wmi_read,
        .unlocked_ioctl = dell_smbios_wmi_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
};

static void dell_smbios_wmi_unregister_chardev(void *data)
{
        struct miscdevice *char_dev = data;

        misc_deregister(char_dev);
}

static int dell_smbios_wmi_register_chardev(struct wmi_smbios_priv *priv)
{
        int ret;

        priv->char_dev.minor = MISC_DYNAMIC_MINOR;
        priv->char_dev.name = "wmi/dell-smbios";
        priv->char_dev.fops = &dell_smbios_wmi_fops;
        priv->char_dev.mode = 0444;

        ret = misc_register(&priv->char_dev);
        if (ret < 0)
                return ret;

        return devm_add_action_or_reset(&priv->wdev->dev, dell_smbios_wmi_unregister_chardev,
                                        &priv->char_dev);
}

static int dell_smbios_wmi_probe(struct wmi_device *wdev, const void *context)
{
        struct wmi_smbios_priv *priv;
        u32 buffer_size, hotfix;
        int count;
        int ret;

        ret = dell_wmi_get_descriptor_valid();
        if (ret)
                return ret;

        priv = devm_kzalloc(&wdev->dev, sizeof(struct wmi_smbios_priv),
                            GFP_KERNEL);
        if (!priv)
                return -ENOMEM;

        priv->wdev = wdev;
        dev_set_drvdata(&wdev->dev, priv);

        /* WMI buffer size will be either 4k or 32k depending on machine */
        if (!dell_wmi_get_size(&buffer_size))
                return -EPROBE_DEFER;

        priv->req_buf_size = buffer_size;

        /* some SMBIOS calls fail unless BIOS contains hotfix */
        if (!dell_wmi_get_hotfix(&hotfix))
                return -EPROBE_DEFER;

        if (!hotfix)
                dev_warn(&wdev->dev,
                        "WMI SMBIOS userspace interface not supported(%u), try upgrading to a newer BIOS\n",
                        hotfix);

        /* add in the length object we will use internally with ioctl */
        priv->req_buf_size += sizeof(u64);

        count = get_order(priv->req_buf_size);
        priv->buf = (void *)devm_get_free_pages(&wdev->dev, GFP_KERNEL, count);
        if (!priv->buf)
                return -ENOMEM;

        ret = dell_smbios_wmi_register_chardev(priv);
        if (ret)
                return ret;

        ret = dell_smbios_register_device(&wdev->dev, 1, &dell_smbios_wmi_call);
        if (ret)
                return ret;

        mutex_lock(&list_mutex);
        list_add_tail(&priv->list, &wmi_list);
        mutex_unlock(&list_mutex);

        return 0;
}

static void dell_smbios_wmi_remove(struct wmi_device *wdev)
{
        struct wmi_smbios_priv *priv = dev_get_drvdata(&wdev->dev);

        mutex_lock(&call_mutex);
        mutex_lock(&list_mutex);
        list_del(&priv->list);
        mutex_unlock(&list_mutex);
        dell_smbios_unregister_device(&wdev->dev);
        mutex_unlock(&call_mutex);
}

static const struct wmi_device_id dell_smbios_wmi_id_table[] = {
        { .guid_string = DELL_WMI_SMBIOS_GUID },
        { },
};

static void parse_b1_table(const struct dmi_header *dm)
{
        struct misc_bios_flags_structure *flags =
        container_of(dm, struct misc_bios_flags_structure, header);

        /* 4 bytes header, 8 bytes flags */
        if (dm->length < 12)
                return;
        if (dm->handle != 0xb100)
                return;
        if ((flags->flags0 & FLAG_HAS_ACPI_WMI))
                wmi_supported = 1;
}

static void find_b1(const struct dmi_header *dm, void *dummy)
{
        switch (dm->type) {
        case 0xb1: /* misc bios flags */
                parse_b1_table(dm);
                break;
        }
}

static struct wmi_driver dell_smbios_wmi_driver = {
        .driver = {
                .name = "dell-smbios",
        },
        .probe = dell_smbios_wmi_probe,
        .remove = dell_smbios_wmi_remove,
        .id_table = dell_smbios_wmi_id_table,
};

int init_dell_smbios_wmi(void)
{
        dmi_walk(find_b1, NULL);

        if (!wmi_supported)
                return -ENODEV;

        return wmi_driver_register(&dell_smbios_wmi_driver);
}

void exit_dell_smbios_wmi(void)
{
        if (wmi_supported)
                wmi_driver_unregister(&dell_smbios_wmi_driver);
}

MODULE_DEVICE_TABLE(wmi, dell_smbios_wmi_id_table);