// SPDX-License-Identifier: GPL-2.0-only
/*
 * predator_wmi -- minimal WMI method bridge for Acer Predator laptops.
 *
 * Binds to the Acer gaming WMI interfaces that mainline acer-wmi does not
 * bind as a driver and exposes one root-only sysfs attribute per device:
 *
 *   /sys/bus/wmi/devices/<GUID>-<n>/predator_call
 *
 *   write: "<method-id> <hex-input-bytes>"   e.g. "20 0300ff00010000ff0302000000000000"
 *   read : "ok buf <hex>" | "ok int <hex u64>" | "ok none" | "err <errno>"
 *
 * The read returns the result of the most recent write. All protocol
 * knowledge lives in userspace (predator-control daemon); this module only
 * moves bytes between sysfs and wmidev_evaluate_method().
 *
 * Interfaces (PH16-71):
 *   7A4DDFE7-...  WMBH  AcerGamingFunction (fans, lightbar, misc settings)
 *   79772EC5-...  WMBE  Battery health (80 % limit, calibration)
 *   61EF69EA-...  WMAA  APGE action (USB charging, backlight timeout)
 */

#include <linux/acpi.h>
#include <linux/ctype.h>
#include <linux/device.h>
#include <linux/dmi.h>
#if __has_include(<linux/hex.h>)
#include <linux/hex.h>
#endif
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/sysfs.h>
#include <linux/wmi.h>

#define PWMI_MAX_IN   64
#define PWMI_MAX_OUT  256

struct pwmi_dev {
	struct wmi_device *wdev;
	struct mutex lock;
	int last_err;
	u8 last_type;                 /* 0 none, 1 buffer, 2 integer */
	size_t last_len;
	u8 last_out[PWMI_MAX_OUT];
	u64 last_int;
};

static ssize_t predator_call_store(struct device *dev,
				   struct device_attribute *attr,
				   const char *buf, size_t count)
{
	struct pwmi_dev *p = dev_get_drvdata(dev);
	struct acpi_buffer out = { ACPI_ALLOCATE_BUFFER, NULL };
	struct acpi_buffer in;
	union acpi_object *obj;
	u8 inbuf[PWMI_MAX_IN];
	const char *s = buf, *end = buf + count;
	unsigned int method = 0;
	size_t n = 0;
	acpi_status status;
	int hi, lo;

	/* method id (decimal) */
	while (s < end && isspace(*s))
		s++;
	if (s >= end || !isdigit(*s))
		return -EINVAL;
	while (s < end && isdigit(*s)) {
		method = method * 10 + (*s - '0');
		if (method > 0xffff)
			return -EINVAL;
		s++;
	}
	while (s < end && isspace(*s))
		s++;

	/* hex payload */
	while (s + 1 < end && !isspace(*s)) {
		hi = hex_to_bin(s[0]);
		lo = hex_to_bin(s[1]);
		if (hi < 0 || lo < 0 || n >= PWMI_MAX_IN)
			return -EINVAL;
		inbuf[n++] = (hi << 4) | lo;
		s += 2;
	}
	while (s < end && isspace(*s))
		s++;
	if (s != end)
		return -EINVAL;

	in.length = n;
	in.pointer = inbuf;

	mutex_lock(&p->lock);
	p->last_type = 0;
	p->last_len = 0;
	p->last_err = 0;

	status = wmidev_evaluate_method(p->wdev, 0, method, &in, &out);
	if (ACPI_FAILURE(status)) {
		p->last_err = -EIO;
		goto unlock;
	}

	obj = out.pointer;
	if (obj && obj->type == ACPI_TYPE_BUFFER) {
		p->last_type = 1;
		p->last_len = min_t(size_t, obj->buffer.length, PWMI_MAX_OUT);
		memcpy(p->last_out, obj->buffer.pointer, p->last_len);
	} else if (obj && obj->type == ACPI_TYPE_INTEGER) {
		p->last_type = 2;
		p->last_int = obj->integer.value;
	}
	kfree(out.pointer);
unlock:
	mutex_unlock(&p->lock);
	return p->last_err ? p->last_err : count;
}

static ssize_t predator_call_show(struct device *dev,
				  struct device_attribute *attr, char *buf)
{
	struct pwmi_dev *p = dev_get_drvdata(dev);
	ssize_t len;

	mutex_lock(&p->lock);
	if (p->last_err)
		len = sysfs_emit(buf, "err %d\n", p->last_err);
	else if (p->last_type == 1)
		len = sysfs_emit(buf, "ok buf %*phN\n", (int)p->last_len,
				 p->last_out);
	else if (p->last_type == 2)
		len = sysfs_emit(buf, "ok int %016llx\n", p->last_int);
	else
		len = sysfs_emit(buf, "ok none\n");
	mutex_unlock(&p->lock);
	return len;
}
static DEVICE_ATTR_ADMIN_RW(predator_call);

static struct attribute *pwmi_attrs[] = {
	&dev_attr_predator_call.attr,
	NULL,
};
ATTRIBUTE_GROUPS(pwmi);

static int pwmi_probe(struct wmi_device *wdev, const void *ctx)
{
	struct pwmi_dev *p;

	p = devm_kzalloc(&wdev->dev, sizeof(*p), GFP_KERNEL);
	if (!p)
		return -ENOMEM;
	p->wdev = wdev;
	mutex_init(&p->lock);
	dev_set_drvdata(&wdev->dev, p);
	return 0;
}

static const struct wmi_device_id pwmi_id_table[] = {
	{ .guid_string = "7A4DDFE7-5B5D-40B4-8595-4408E0CC7F56" },
	{ .guid_string = "79772EC5-04B1-4BFD-843C-61E7F77B6CC9" },
	{ .guid_string = "61EF69EA-865C-4BC3-A502-A0DEBA0CB531" },
	{ }
};
MODULE_DEVICE_TABLE(wmi, pwmi_id_table);

static struct wmi_driver pwmi_driver = {
	.driver = {
		.name = "predator_wmi",
		.dev_groups = pwmi_groups,
	},
	.id_table = pwmi_id_table,
	.probe = pwmi_probe,
	.no_singleton = true,
};

static const struct dmi_system_id pwmi_dmi[] = {
	{ .matches = { DMI_MATCH(DMI_SYS_VENDOR, "Acer") } },
	{ }
};

static int __init pwmi_init(void)
{
	if (!dmi_check_system(pwmi_dmi))
		return -ENODEV;
	return wmi_driver_register(&pwmi_driver);
}

static void __exit pwmi_exit(void)
{
	wmi_driver_unregister(&pwmi_driver);
}

module_init(pwmi_init);
module_exit(pwmi_exit);

MODULE_AUTHOR("predator-control");
MODULE_DESCRIPTION("WMI method bridge for Acer Predator laptops");
MODULE_LICENSE("GPL");