// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Virtual Raw MIDI client on Sequencer
 *
 *  Copyright (c) 2000 by Takashi Iwai <tiwai@suse.de>,
 *                        Jaroslav Kysela <perex@perex.cz>
 */

/*
 * Virtual Raw MIDI client
 *
 * The virtual rawmidi client is a sequencer client which associate
 * a rawmidi device file.  The created rawmidi device file can be
 * accessed as a normal raw midi, but its MIDI source and destination
 * are arbitrary.  For example, a user-client software synth connected
 * to this port can be used as a normal midi device as well.
 *
 * The virtual rawmidi device accepts also multiple opens.  Each file
 * has its own input buffer, so that no conflict would occur.  The drain
 * of input/output buffer acts only to the local buffer.
 *
 */

#include <linux/init.h>
#include <linux/wait.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <sound/core.h>
#include <sound/rawmidi.h>
#include <sound/info.h>
#include <sound/control.h>
#include <sound/minors.h>
#include <sound/seq_kernel.h>
#include <sound/seq_midi_event.h>
#include <sound/seq_virmidi.h>

MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
MODULE_DESCRIPTION("Virtual Raw MIDI client on Sequencer");
MODULE_LICENSE("GPL");

/*
 * initialize an event record
 */
static void snd_virmidi_init_event(struct snd_virmidi *vmidi,
                                   struct snd_seq_event *ev)
{
        memset(ev, 0, sizeof(*ev));
        ev->source.port = vmidi->port;
        switch (vmidi->seq_mode) {
        case SNDRV_VIRMIDI_SEQ_DISPATCH:
                ev->dest.client = SNDRV_SEQ_ADDRESS_SUBSCRIBERS;
                break;
        case SNDRV_VIRMIDI_SEQ_ATTACH:
                /* FIXME: source and destination are same - not good.. */
                ev->dest.client = vmidi->client;
                ev->dest.port = vmidi->port;
                break;
        }
        ev->type = SNDRV_SEQ_EVENT_NONE;
}

/*
 * decode input event and put to read buffer of each opened file
 */

/* callback for snd_seq_dump_var_event(), bridging to snd_rawmidi_receive() */
static int dump_to_rawmidi(void *ptr, void *buf, int count)
{
        return snd_rawmidi_receive(ptr, buf, count);
}

static int snd_virmidi_dev_receive_event(struct snd_virmidi_dev *rdev,
                                         struct snd_seq_event *ev,
                                         bool atomic)
{
        struct snd_virmidi *vmidi;
        unsigned char msg[4];
        int len;

        if (atomic)
                read_lock(&rdev->filelist_lock);
        else
                down_read(&rdev->filelist_sem);
        list_for_each_entry(vmidi, &rdev->filelist, list) {
                if (!READ_ONCE(vmidi->trigger))
                        continue;
                if (ev->type == SNDRV_SEQ_EVENT_SYSEX) {
                        if ((ev->flags & SNDRV_SEQ_EVENT_LENGTH_MASK) != SNDRV_SEQ_EVENT_LENGTH_VARIABLE)
                                continue;
                        snd_seq_dump_var_event(ev, dump_to_rawmidi, vmidi->substream);
                        snd_midi_event_reset_decode(vmidi->parser);
                } else {
                        len = snd_midi_event_decode(vmidi->parser, msg, sizeof(msg), ev);
                        if (len > 0)
                                snd_rawmidi_receive(vmidi->substream, msg, len);
                }
        }
        if (atomic)
                read_unlock(&rdev->filelist_lock);
        else
                up_read(&rdev->filelist_sem);

        return 0;
}

/*
 * event handler of virmidi port
 */
static int snd_virmidi_event_input(struct snd_seq_event *ev, int direct,
                                   void *private_data, int atomic, int hop)
{
        struct snd_virmidi_dev *rdev;

        rdev = private_data;
        if (!(rdev->flags & SNDRV_VIRMIDI_USE))
                return 0; /* ignored */
        return snd_virmidi_dev_receive_event(rdev, ev, atomic);
}

/*
 * trigger rawmidi stream for input
 */
static void snd_virmidi_input_trigger(struct snd_rawmidi_substream *substream, int up)
{
        struct snd_virmidi *vmidi = substream->runtime->private_data;

        WRITE_ONCE(vmidi->trigger, !!up);
}

/* process rawmidi bytes and send events;
 * we need no lock here for vmidi->event since it's handled only in this work
 */
static void snd_vmidi_output_work(struct work_struct *work)
{
        struct snd_virmidi *vmidi;
        struct snd_rawmidi_substream *substream;
        unsigned char input;
        int ret;

        vmidi = container_of(work, struct snd_virmidi, output_work);
        substream = vmidi->substream;

        /* discard the outputs in dispatch mode unless subscribed */
        if (vmidi->seq_mode == SNDRV_VIRMIDI_SEQ_DISPATCH &&
            !(vmidi->rdev->flags & SNDRV_VIRMIDI_SUBSCRIBE)) {
                snd_rawmidi_proceed(substream);
                return;
        }

        while (READ_ONCE(vmidi->trigger)) {
                if (snd_rawmidi_transmit(substream, &input, 1) != 1)
                        break;
                if (!snd_midi_event_encode_byte(vmidi->parser, input,
                                                &vmidi->event))
                        continue;
                if (vmidi->event.type != SNDRV_SEQ_EVENT_NONE) {
                        ret = snd_seq_kernel_client_dispatch(vmidi->client,
                                                             &vmidi->event,
                                                             false, 0);
                        vmidi->event.type = SNDRV_SEQ_EVENT_NONE;
                        if (ret < 0)
                                break;
                }
                /* rawmidi input might be huge, allow to have a break */
                cond_resched();
        }
}

/*
 * trigger rawmidi stream for output
 */
static void snd_virmidi_output_trigger(struct snd_rawmidi_substream *substream, int up)
{
        struct snd_virmidi *vmidi = substream->runtime->private_data;

        WRITE_ONCE(vmidi->trigger, !!up);
        if (up)
                queue_work(system_highpri_wq, &vmidi->output_work);
}

/*
 * open rawmidi handle for input
 */
static int snd_virmidi_input_open(struct snd_rawmidi_substream *substream)
{
        struct snd_virmidi_dev *rdev = substream->rmidi->private_data;
        struct snd_rawmidi_runtime *runtime = substream->runtime;
        struct snd_virmidi *vmidi;

        vmidi = kzalloc(sizeof(*vmidi), GFP_KERNEL);
        if (vmidi == NULL)
                return -ENOMEM;
        vmidi->substream = substream;
        if (snd_midi_event_new(0, &vmidi->parser) < 0) {
                kfree(vmidi);
                return -ENOMEM;
        }
        vmidi->seq_mode = rdev->seq_mode;
        vmidi->client = rdev->client;
        vmidi->port = rdev->port;       
        runtime->private_data = vmidi;
        scoped_guard(rwsem_write, &rdev->filelist_sem) {
                guard(write_lock_irq)(&rdev->filelist_lock);
                list_add_tail(&vmidi->list, &rdev->filelist);
        }
        vmidi->rdev = rdev;
        return 0;
}

/*
 * open rawmidi handle for output
 */
static int snd_virmidi_output_open(struct snd_rawmidi_substream *substream)
{
        struct snd_virmidi_dev *rdev = substream->rmidi->private_data;
        struct snd_rawmidi_runtime *runtime = substream->runtime;
        struct snd_virmidi *vmidi;

        vmidi = kzalloc_obj(*vmidi);
        if (vmidi == NULL)
                return -ENOMEM;
        vmidi->substream = substream;
        if (snd_midi_event_new(MAX_MIDI_EVENT_BUF, &vmidi->parser) < 0) {
                kfree(vmidi);
                return -ENOMEM;
        }
        vmidi->seq_mode = rdev->seq_mode;
        vmidi->client = rdev->client;
        vmidi->port = rdev->port;
        snd_virmidi_init_event(vmidi, &vmidi->event);
        vmidi->rdev = rdev;
        INIT_WORK(&vmidi->output_work, snd_vmidi_output_work);
        runtime->private_data = vmidi;
        return 0;
}

/*
 * close rawmidi handle for input
 */
static int snd_virmidi_input_close(struct snd_rawmidi_substream *substream)
{
        struct snd_virmidi_dev *rdev = substream->rmidi->private_data;
        struct snd_virmidi *vmidi = substream->runtime->private_data;

        scoped_guard(rwsem_write, &rdev->filelist_sem) {
                guard(write_lock_irq)(&rdev->filelist_lock);
                list_del(&vmidi->list);
        }
        snd_midi_event_free(vmidi->parser);
        substream->runtime->private_data = NULL;
        kfree(vmidi);
        return 0;
}

/*
 * close rawmidi handle for output
 */
static int snd_virmidi_output_close(struct snd_rawmidi_substream *substream)
{
        struct snd_virmidi *vmidi = substream->runtime->private_data;

        WRITE_ONCE(vmidi->trigger, false); /* to be sure */
        cancel_work_sync(&vmidi->output_work);
        snd_midi_event_free(vmidi->parser);
        substream->runtime->private_data = NULL;
        kfree(vmidi);
        return 0;
}

/*
 * drain output work queue
 */
static void snd_virmidi_output_drain(struct snd_rawmidi_substream *substream)
{
        struct snd_virmidi *vmidi = substream->runtime->private_data;

        flush_work(&vmidi->output_work);
}

/*
 * subscribe callback - allow output to rawmidi device
 */
static int snd_virmidi_subscribe(void *private_data,
                                 struct snd_seq_port_subscribe *info)
{
        struct snd_virmidi_dev *rdev;

        rdev = private_data;
        if (!try_module_get(rdev->card->module))
                return -EFAULT;
        rdev->flags |= SNDRV_VIRMIDI_SUBSCRIBE;
        return 0;
}

/*
 * unsubscribe callback - disallow output to rawmidi device
 */
static int snd_virmidi_unsubscribe(void *private_data,
                                   struct snd_seq_port_subscribe *info)
{
        struct snd_virmidi_dev *rdev;

        rdev = private_data;
        rdev->flags &= ~SNDRV_VIRMIDI_SUBSCRIBE;
        module_put(rdev->card->module);
        return 0;
}


/*
 * use callback - allow input to rawmidi device
 */
static int snd_virmidi_use(void *private_data,
                           struct snd_seq_port_subscribe *info)
{
        struct snd_virmidi_dev *rdev;

        rdev = private_data;
        if (!try_module_get(rdev->card->module))
                return -EFAULT;
        rdev->flags |= SNDRV_VIRMIDI_USE;
        return 0;
}

/*
 * unuse callback - disallow input to rawmidi device
 */
static int snd_virmidi_unuse(void *private_data,
                             struct snd_seq_port_subscribe *info)
{
        struct snd_virmidi_dev *rdev;

        rdev = private_data;
        rdev->flags &= ~SNDRV_VIRMIDI_USE;
        module_put(rdev->card->module);
        return 0;
}


/*
 *  Register functions
 */

static const struct snd_rawmidi_ops snd_virmidi_input_ops = {
        .open = snd_virmidi_input_open,
        .close = snd_virmidi_input_close,
        .trigger = snd_virmidi_input_trigger,
};

static const struct snd_rawmidi_ops snd_virmidi_output_ops = {
        .open = snd_virmidi_output_open,
        .close = snd_virmidi_output_close,
        .trigger = snd_virmidi_output_trigger,
        .drain = snd_virmidi_output_drain,
};

/*
 * create a sequencer client and a port
 */
static int snd_virmidi_dev_attach_seq(struct snd_virmidi_dev *rdev)
{
        int client;
        struct snd_seq_port_callback pcallbacks;
        int err;

        if (rdev->client >= 0)
                return 0;

        struct snd_seq_port_info *pinfo __free(kfree) =
                kzalloc_obj(*pinfo);
        if (!pinfo)
                return -ENOMEM;

        client = snd_seq_create_kernel_client(rdev->card, rdev->device,
                                              "%s %d-%d", rdev->rmidi->name,
                                              rdev->card->number,
                                              rdev->device);
        if (client < 0)
                return client;
        rdev->client = client;

        /* create a port */
        pinfo->addr.client = client;
        sprintf(pinfo->name, "VirMIDI %d-%d", rdev->card->number, rdev->device);
        /* set all capabilities */
        pinfo->capability |= SNDRV_SEQ_PORT_CAP_WRITE | SNDRV_SEQ_PORT_CAP_SYNC_WRITE | SNDRV_SEQ_PORT_CAP_SUBS_WRITE;
        pinfo->capability |= SNDRV_SEQ_PORT_CAP_READ | SNDRV_SEQ_PORT_CAP_SYNC_READ | SNDRV_SEQ_PORT_CAP_SUBS_READ;
        pinfo->capability |= SNDRV_SEQ_PORT_CAP_DUPLEX;
        pinfo->direction = SNDRV_SEQ_PORT_DIR_BIDIRECTION;
        pinfo->type = SNDRV_SEQ_PORT_TYPE_MIDI_GENERIC
                | SNDRV_SEQ_PORT_TYPE_SOFTWARE
                | SNDRV_SEQ_PORT_TYPE_PORT;
        pinfo->midi_channels = 16;
        memset(&pcallbacks, 0, sizeof(pcallbacks));
        pcallbacks.owner = THIS_MODULE;
        pcallbacks.private_data = rdev;
        pcallbacks.subscribe = snd_virmidi_subscribe;
        pcallbacks.unsubscribe = snd_virmidi_unsubscribe;
        pcallbacks.use = snd_virmidi_use;
        pcallbacks.unuse = snd_virmidi_unuse;
        pcallbacks.event_input = snd_virmidi_event_input;
        pinfo->kernel = &pcallbacks;
        err = snd_seq_kernel_client_ctl(client, SNDRV_SEQ_IOCTL_CREATE_PORT, pinfo);
        if (err < 0) {
                snd_seq_delete_kernel_client(client);
                rdev->client = -1;
                return err;
        }

        rdev->port = pinfo->addr.port;
        return 0; /* success */
}


/*
 * release the sequencer client
 */
static void snd_virmidi_dev_detach_seq(struct snd_virmidi_dev *rdev)
{
        if (rdev->client >= 0) {
                snd_seq_delete_kernel_client(rdev->client);
                rdev->client = -1;
        }
}

/*
 * register the device
 */
static int snd_virmidi_dev_register(struct snd_rawmidi *rmidi)
{
        struct snd_virmidi_dev *rdev = rmidi->private_data;
        int err;

        switch (rdev->seq_mode) {
        case SNDRV_VIRMIDI_SEQ_DISPATCH:
                err = snd_virmidi_dev_attach_seq(rdev);
                if (err < 0)
                        return err;
                break;
        case SNDRV_VIRMIDI_SEQ_ATTACH:
                if (rdev->client == 0)
                        return -EINVAL;
                /* should check presence of port more strictly.. */
                break;
        default:
                pr_err("ALSA: seq_virmidi: seq_mode is not set: %d\n", rdev->seq_mode);
                return -EINVAL;
        }
        return 0;
}


/*
 * unregister the device
 */
static int snd_virmidi_dev_unregister(struct snd_rawmidi *rmidi)
{
        struct snd_virmidi_dev *rdev = rmidi->private_data;

        if (rdev->seq_mode == SNDRV_VIRMIDI_SEQ_DISPATCH)
                snd_virmidi_dev_detach_seq(rdev);
        return 0;
}

/*
 *
 */
static const struct snd_rawmidi_global_ops snd_virmidi_global_ops = {
        .dev_register = snd_virmidi_dev_register,
        .dev_unregister = snd_virmidi_dev_unregister,
};

/*
 * free device
 */
static void snd_virmidi_free(struct snd_rawmidi *rmidi)
{
        struct snd_virmidi_dev *rdev = rmidi->private_data;
        kfree(rdev);
}

/*
 * create a new device
 *
 */
/* exported */
int snd_virmidi_new(struct snd_card *card, int device, struct snd_rawmidi **rrmidi)
{
        struct snd_rawmidi *rmidi;
        struct snd_virmidi_dev *rdev;
        int err;
        
        *rrmidi = NULL;
        err = snd_rawmidi_new(card, "VirMidi", device,
                              16,       /* may be configurable */
                              16,       /* may be configurable */
                              &rmidi);
        if (err < 0)
                return err;
        strscpy(rmidi->name, rmidi->id);
        rdev = kzalloc_obj(*rdev);
        if (rdev == NULL) {
                snd_device_free(card, rmidi);
                return -ENOMEM;
        }
        rdev->card = card;
        rdev->rmidi = rmidi;
        rdev->device = device;
        rdev->client = -1;
        init_rwsem(&rdev->filelist_sem);
        rwlock_init(&rdev->filelist_lock);
        INIT_LIST_HEAD(&rdev->filelist);
        rdev->seq_mode = SNDRV_VIRMIDI_SEQ_DISPATCH;
        rmidi->private_data = rdev;
        rmidi->private_free = snd_virmidi_free;
        rmidi->ops = &snd_virmidi_global_ops;
        snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_INPUT, &snd_virmidi_input_ops);
        snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_OUTPUT, &snd_virmidi_output_ops);
        rmidi->info_flags = SNDRV_RAWMIDI_INFO_INPUT |
                            SNDRV_RAWMIDI_INFO_OUTPUT |
                            SNDRV_RAWMIDI_INFO_DUPLEX;
        *rrmidi = rmidi;
        return 0;
}
EXPORT_SYMBOL(snd_virmidi_new);