// SPDX-License-Identifier: GPL-2.0 OR MIT

/*
 * Xen para-virtual sound device
 *
 * Copyright (C) 2016-2018 EPAM Systems Inc.
 *
 * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
 */

#include <linux/delay.h>
#include <linux/module.h>

#include <xen/page.h>
#include <xen/platform_pci.h>
#include <xen/xen.h>
#include <xen/xenbus.h>

#include <xen/xen-front-pgdir-shbuf.h>
#include <xen/interface/io/sndif.h>

#include "xen_snd_front.h"
#include "xen_snd_front_alsa.h"
#include "xen_snd_front_evtchnl.h"

static struct xensnd_req *
be_stream_prepare_req(struct xen_snd_front_evtchnl *evtchnl, u8 operation)
{
        struct xensnd_req *req;

        req = RING_GET_REQUEST(&evtchnl->u.req.ring,
                               evtchnl->u.req.ring.req_prod_pvt);
        req->operation = operation;
        req->id = evtchnl->evt_next_id++;
        evtchnl->evt_id = req->id;
        return req;
}

static int be_stream_do_io(struct xen_snd_front_evtchnl *evtchnl)
{
        if (unlikely(evtchnl->state != EVTCHNL_STATE_CONNECTED))
                return -EIO;

        reinit_completion(&evtchnl->u.req.completion);
        xen_snd_front_evtchnl_flush(evtchnl);
        return 0;
}

static int be_stream_wait_io(struct xen_snd_front_evtchnl *evtchnl)
{
        if (wait_for_completion_timeout(&evtchnl->u.req.completion,
                        msecs_to_jiffies(VSND_WAIT_BACK_MS)) <= 0)
                return -ETIMEDOUT;

        return evtchnl->u.req.resp_status;
}

int xen_snd_front_stream_query_hw_param(struct xen_snd_front_evtchnl *evtchnl,
                                        struct xensnd_query_hw_param *hw_param_req,
                                        struct xensnd_query_hw_param *hw_param_resp)
{
        struct xensnd_req *req;
        int ret;

        guard(mutex)(&evtchnl->u.req.req_io_lock);

        scoped_guard(mutex, &evtchnl->ring_io_lock) {
                req = be_stream_prepare_req(evtchnl, XENSND_OP_HW_PARAM_QUERY);
                req->op.hw_param = *hw_param_req;
        }

        ret = be_stream_do_io(evtchnl);

        if (ret == 0)
                ret = be_stream_wait_io(evtchnl);

        if (ret == 0)
                *hw_param_resp = evtchnl->u.req.resp.hw_param;

        return ret;
}

int xen_snd_front_stream_prepare(struct xen_snd_front_evtchnl *evtchnl,
                                 struct xen_front_pgdir_shbuf *shbuf,
                                 u8 format, unsigned int channels,
                                 unsigned int rate, u32 buffer_sz,
                                 u32 period_sz)
{
        struct xensnd_req *req;
        int ret;

        guard(mutex)(&evtchnl->u.req.req_io_lock);

        scoped_guard(mutex, &evtchnl->ring_io_lock) {
                req = be_stream_prepare_req(evtchnl, XENSND_OP_OPEN);
                req->op.open.pcm_format = format;
                req->op.open.pcm_channels = channels;
                req->op.open.pcm_rate = rate;
                req->op.open.buffer_sz = buffer_sz;
                req->op.open.period_sz = period_sz;
                req->op.open.gref_directory =
                        xen_front_pgdir_shbuf_get_dir_start(shbuf);
        }

        ret = be_stream_do_io(evtchnl);

        if (ret == 0)
                ret = be_stream_wait_io(evtchnl);

        return ret;
}

int xen_snd_front_stream_close(struct xen_snd_front_evtchnl *evtchnl)
{
        __always_unused struct xensnd_req *req;
        int ret;

        guard(mutex)(&evtchnl->u.req.req_io_lock);

        scoped_guard(mutex, &evtchnl->ring_io_lock) {
                req = be_stream_prepare_req(evtchnl, XENSND_OP_CLOSE);
        }

        ret = be_stream_do_io(evtchnl);

        if (ret == 0)
                ret = be_stream_wait_io(evtchnl);

        return ret;
}

int xen_snd_front_stream_write(struct xen_snd_front_evtchnl *evtchnl,
                               unsigned long pos, unsigned long count)
{
        struct xensnd_req *req;
        int ret;

        guard(mutex)(&evtchnl->u.req.req_io_lock);

        scoped_guard(mutex, &evtchnl->ring_io_lock) {
                req = be_stream_prepare_req(evtchnl, XENSND_OP_WRITE);
                req->op.rw.length = count;
                req->op.rw.offset = pos;
        }

        ret = be_stream_do_io(evtchnl);

        if (ret == 0)
                ret = be_stream_wait_io(evtchnl);

        return ret;
}

int xen_snd_front_stream_read(struct xen_snd_front_evtchnl *evtchnl,
                              unsigned long pos, unsigned long count)
{
        struct xensnd_req *req;
        int ret;

        guard(mutex)(&evtchnl->u.req.req_io_lock);

        scoped_guard(mutex, &evtchnl->ring_io_lock) {
                req = be_stream_prepare_req(evtchnl, XENSND_OP_READ);
                req->op.rw.length = count;
                req->op.rw.offset = pos;
        }

        ret = be_stream_do_io(evtchnl);

        if (ret == 0)
                ret = be_stream_wait_io(evtchnl);

        return ret;
}

int xen_snd_front_stream_trigger(struct xen_snd_front_evtchnl *evtchnl,
                                 int type)
{
        struct xensnd_req *req;
        int ret;

        guard(mutex)(&evtchnl->u.req.req_io_lock);

        scoped_guard(mutex, &evtchnl->ring_io_lock) {
                req = be_stream_prepare_req(evtchnl, XENSND_OP_TRIGGER);
                req->op.trigger.type = type;
        }

        ret = be_stream_do_io(evtchnl);

        if (ret == 0)
                ret = be_stream_wait_io(evtchnl);

        return ret;
}

static void xen_snd_drv_fini(struct xen_snd_front_info *front_info)
{
        xen_snd_front_alsa_fini(front_info);
        xen_snd_front_evtchnl_free_all(front_info);
}

static int sndback_initwait(struct xen_snd_front_info *front_info)
{
        int num_streams;
        int ret;

        ret = xen_snd_front_cfg_card(front_info, &num_streams);
        if (ret < 0)
                return ret;

        /* create event channels for all streams and publish */
        ret = xen_snd_front_evtchnl_create_all(front_info, num_streams);
        if (ret < 0)
                return ret;

        return xen_snd_front_evtchnl_publish_all(front_info);
}

static int sndback_connect(struct xen_snd_front_info *front_info)
{
        return xen_snd_front_alsa_init(front_info);
}

static void sndback_disconnect(struct xen_snd_front_info *front_info)
{
        xen_snd_drv_fini(front_info);
        xenbus_switch_state(front_info->xb_dev, XenbusStateInitialising);
}

static void sndback_changed(struct xenbus_device *xb_dev,
                            enum xenbus_state backend_state)
{
        struct xen_snd_front_info *front_info = dev_get_drvdata(&xb_dev->dev);
        int ret;

        dev_dbg(&xb_dev->dev, "Backend state is %s, front is %s\n",
                xenbus_strstate(backend_state),
                xenbus_strstate(xb_dev->state));

        switch (backend_state) {
        case XenbusStateReconfiguring:
        case XenbusStateReconfigured:
        case XenbusStateInitialised:
                break;

        case XenbusStateInitialising:
                /* Recovering after backend unexpected closure. */
                sndback_disconnect(front_info);
                break;

        case XenbusStateInitWait:
                /* Recovering after backend unexpected closure. */
                sndback_disconnect(front_info);

                ret = sndback_initwait(front_info);
                if (ret < 0)
                        xenbus_dev_fatal(xb_dev, ret, "initializing frontend");
                else
                        xenbus_switch_state(xb_dev, XenbusStateInitialised);
                break;

        case XenbusStateConnected:
                if (xb_dev->state != XenbusStateInitialised)
                        break;

                ret = sndback_connect(front_info);
                if (ret < 0)
                        xenbus_dev_fatal(xb_dev, ret, "initializing frontend");
                else
                        xenbus_switch_state(xb_dev, XenbusStateConnected);
                break;

        case XenbusStateClosing:
                /*
                 * In this state backend starts freeing resources,
                 * so let it go into closed state first, so we can also
                 * remove ours.
                 */
                break;

        case XenbusStateUnknown:
        case XenbusStateClosed:
                if (xb_dev->state == XenbusStateClosed)
                        break;

                sndback_disconnect(front_info);
                break;
        }
}

static int xen_drv_probe(struct xenbus_device *xb_dev,
                         const struct xenbus_device_id *id)
{
        struct xen_snd_front_info *front_info;

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

        front_info->xb_dev = xb_dev;
        dev_set_drvdata(&xb_dev->dev, front_info);

        return xenbus_switch_state(xb_dev, XenbusStateInitialising);
}

static void xen_drv_remove(struct xenbus_device *dev)
{
        struct xen_snd_front_info *front_info = dev_get_drvdata(&dev->dev);
        int to = 100;

        xenbus_switch_state(dev, XenbusStateClosing);

        /*
         * On driver removal it is disconnected from XenBus,
         * so no backend state change events come via .otherend_changed
         * callback. This prevents us from exiting gracefully, e.g.
         * signaling the backend to free event channels, waiting for its
         * state to change to XenbusStateClosed and cleaning at our end.
         * Normally when front driver removed backend will finally go into
         * XenbusStateInitWait state.
         *
         * Workaround: read backend's state manually and wait with time-out.
         */
        while ((xenbus_read_unsigned(front_info->xb_dev->otherend, "state",
                                     XenbusStateUnknown) != XenbusStateInitWait) &&
               --to)
                msleep(10);

        if (!to) {
                unsigned int state;

                state = xenbus_read_unsigned(front_info->xb_dev->otherend,
                                             "state", XenbusStateUnknown);
                pr_err("Backend state is %s while removing driver\n",
                       xenbus_strstate(state));
        }

        xen_snd_drv_fini(front_info);
        xenbus_frontend_closed(dev);
}

static const struct xenbus_device_id xen_drv_ids[] = {
        { XENSND_DRIVER_NAME },
        { "" }
};

static struct xenbus_driver xen_driver = {
        .ids = xen_drv_ids,
        .probe = xen_drv_probe,
        .remove = xen_drv_remove,
        .otherend_changed = sndback_changed,
        .not_essential = true,
};

static int __init xen_drv_init(void)
{
        if (!xen_domain())
                return -ENODEV;

        if (!xen_has_pv_devices())
                return -ENODEV;

        /* At the moment we only support case with XEN_PAGE_SIZE == PAGE_SIZE */
        if (XEN_PAGE_SIZE != PAGE_SIZE) {
                pr_err(XENSND_DRIVER_NAME ": different kernel and Xen page sizes are not supported: XEN_PAGE_SIZE (%lu) != PAGE_SIZE (%lu)\n",
                       XEN_PAGE_SIZE, PAGE_SIZE);
                return -ENODEV;
        }

        pr_info("Initialising Xen " XENSND_DRIVER_NAME " frontend driver\n");
        return xenbus_register_frontend(&xen_driver);
}

static void __exit xen_drv_fini(void)
{
        pr_info("Unregistering Xen " XENSND_DRIVER_NAME " frontend driver\n");
        xenbus_unregister_driver(&xen_driver);
}

module_init(xen_drv_init);
module_exit(xen_drv_fini);

MODULE_DESCRIPTION("Xen virtual sound device frontend");
MODULE_LICENSE("GPL");
MODULE_ALIAS("xen:" XENSND_DRIVER_NAME);