/*
 * Generic Event Device for ACPI.
 *
 * Copyright (c) 2016, The Linux Foundation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * Generic Event Device allows platforms to handle interrupts in ACPI
 * ASL statements. It follows very similar to  _EVT method approach
 * from GPIO events. All interrupts are listed in _CRS and the handler
 * is written in _EVT method. Here is an example.
 *
 * Device (GED0)
 * {
 *
 *     Name (_HID, "ACPI0013")
 *     Name (_UID, 0)
 *     Method (_CRS, 0x0, Serialized)
 *     {
 *              Name (RBUF, ResourceTemplate ()
 *              {
 *              Interrupt(ResourceConsumer, Edge, ActiveHigh, Shared, , , )
 *              {123}
 *              }
 *     })
 *
 *     Method (_EVT, 1) {
 *             if (Lequal(123, Arg0))
 *             {
 *             }
 *     }
 * }
 *
 */

#include <linux/err.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/list.h>
#include <linux/platform_device.h>
#include <linux/acpi.h>

#define MODULE_NAME     "acpi-ged"

struct acpi_ged_device {
        struct device *dev;
        struct list_head event_list;
};

struct acpi_ged_event {
        struct list_head node;
        struct device *dev;
        unsigned int gsi;
        unsigned int irq;
        acpi_handle handle;
};

static irqreturn_t acpi_ged_irq_handler(int irq, void *data)
{
        struct acpi_ged_event *event = data;
        acpi_status acpi_ret;

        acpi_ret = acpi_execute_simple_method(event->handle, NULL, event->gsi);
        if (ACPI_FAILURE(acpi_ret))
                dev_err_once(event->dev, "IRQ method execution failed\n");

        return IRQ_HANDLED;
}

static acpi_status acpi_ged_request_interrupt(struct acpi_resource *ares,
                                              void *context)
{
        struct acpi_ged_event *event;
        unsigned int irq;
        unsigned int gsi;
        unsigned int irqflags = IRQF_ONESHOT;
        struct acpi_ged_device *geddev = context;
        struct device *dev = geddev->dev;
        acpi_handle handle = ACPI_HANDLE(dev);
        acpi_handle evt_handle;
        struct resource r;
        struct acpi_resource_irq *p = &ares->data.irq;
        struct acpi_resource_extended_irq *pext = &ares->data.extended_irq;
        char ev_name[5];
        u8 trigger;

        if (ares->type == ACPI_RESOURCE_TYPE_END_TAG)
                return AE_OK;

        if (!acpi_dev_resource_interrupt(ares, 0, &r)) {
                dev_err(dev, "unable to parse IRQ resource\n");
                return AE_ERROR;
        }
        if (ares->type == ACPI_RESOURCE_TYPE_IRQ) {
                gsi = p->interrupts[0];
                trigger = p->triggering;
        } else {
                gsi = pext->interrupts[0];
                trigger = pext->triggering;
        }

        irq = r.start;

        switch (gsi) {
        case 0 ... 255:
                sprintf(ev_name, "_%c%02X",
                        trigger == ACPI_EDGE_SENSITIVE ? 'E' : 'L', gsi);

                if (ACPI_SUCCESS(acpi_get_handle(handle, ev_name, &evt_handle)))
                        break;
                fallthrough;
        default:
                if (ACPI_SUCCESS(acpi_get_handle(handle, "_EVT", &evt_handle)))
                        break;

                dev_err(dev, "cannot locate _EVT method\n");
                return AE_ERROR;
        }

        event = devm_kzalloc(dev, sizeof(*event), GFP_KERNEL);
        if (!event)
                return AE_ERROR;

        event->gsi = gsi;
        event->dev = dev;
        event->irq = irq;
        event->handle = evt_handle;

        if (r.flags & IORESOURCE_IRQ_SHAREABLE)
                irqflags |= IRQF_SHARED;

        if (request_threaded_irq(irq, NULL, acpi_ged_irq_handler,
                                 irqflags, "ACPI:Ged", event)) {
                dev_err(dev, "failed to setup event handler for irq %u\n", irq);
                return AE_ERROR;
        }

        dev_dbg(dev, "GED listening GSI %u @ IRQ %u\n", gsi, irq);
        list_add_tail(&event->node, &geddev->event_list);
        return AE_OK;
}

static int ged_probe(struct platform_device *pdev)
{
        struct acpi_ged_device *geddev;
        acpi_status acpi_ret;

        geddev = devm_kzalloc(&pdev->dev, sizeof(*geddev), GFP_KERNEL);
        if (!geddev)
                return -ENOMEM;

        geddev->dev = &pdev->dev;
        INIT_LIST_HEAD(&geddev->event_list);
        acpi_ret = acpi_walk_resources(ACPI_HANDLE(&pdev->dev), "_CRS",
                                       acpi_ged_request_interrupt, geddev);
        if (ACPI_FAILURE(acpi_ret)) {
                dev_err(&pdev->dev, "unable to parse the _CRS record\n");
                return -EINVAL;
        }
        platform_set_drvdata(pdev, geddev);

        return 0;
}

static void ged_shutdown(struct platform_device *pdev)
{
        struct acpi_ged_device *geddev = platform_get_drvdata(pdev);
        struct acpi_ged_event *event, *next;

        list_for_each_entry_safe(event, next, &geddev->event_list, node) {
                free_irq(event->irq, event);
                list_del(&event->node);
                dev_dbg(geddev->dev, "GED releasing GSI %u @ IRQ %u\n",
                         event->gsi, event->irq);
        }
}

static int ged_remove(struct platform_device *pdev)
{
        ged_shutdown(pdev);
        return 0;
}

static const struct acpi_device_id ged_acpi_ids[] = {
        {"ACPI0013"},
        {},
};

static struct platform_driver ged_driver = {
        .probe = ged_probe,
        .remove = ged_remove,
        .shutdown = ged_shutdown,
        .driver = {
                .name = MODULE_NAME,
                .acpi_match_table = ACPI_PTR(ged_acpi_ids),
        },
};
builtin_platform_driver(ged_driver);