// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *   Generic MIDI synth driver for ALSA sequencer
 *   Copyright (c) 1998 by Frank van de Pol <fvdpol@coil.demon.nl>
 *                         Jaroslav Kysela <perex@perex.cz>
 */
 
/* 
Possible options for midisynth module:
        - automatic opening of midi ports on first received event or subscription
          (close will be performed when client leaves)
*/


#include <linux/init.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <sound/core.h>
#include <sound/rawmidi.h>
#include <sound/seq_kernel.h>
#include <sound/seq_device.h>
#include <sound/seq_midi_event.h>
#include <sound/initval.h>

MODULE_AUTHOR("Frank van de Pol <fvdpol@coil.demon.nl>, Jaroslav Kysela <perex@perex.cz>");
MODULE_DESCRIPTION("Advanced Linux Sound Architecture sequencer MIDI synth.");
MODULE_LICENSE("GPL");
static int output_buffer_size = PAGE_SIZE;
module_param(output_buffer_size, int, 0644);
MODULE_PARM_DESC(output_buffer_size, "Output buffer size in bytes.");
static int input_buffer_size = PAGE_SIZE;
module_param(input_buffer_size, int, 0644);
MODULE_PARM_DESC(input_buffer_size, "Input buffer size in bytes.");

/* data for this midi synth driver */
struct seq_midisynth {
        struct snd_card *card;
        struct snd_rawmidi *rmidi;
        int device;
        int subdevice;
        struct snd_rawmidi_file input_rfile;
        struct snd_rawmidi_file output_rfile;
        int seq_client;
        int seq_port;
        struct snd_midi_event *parser;
};

struct seq_midisynth_client {
        int seq_client;
        int num_ports;
        int ports_per_device[SNDRV_RAWMIDI_DEVICES];
        struct seq_midisynth *ports[SNDRV_RAWMIDI_DEVICES];
};

static struct seq_midisynth_client *synths[SNDRV_CARDS];
static DEFINE_MUTEX(register_mutex);

/* handle rawmidi input event (MIDI v1.0 stream) */
static void snd_midi_input_event(struct snd_rawmidi_substream *substream)
{
        struct snd_rawmidi_runtime *runtime;
        struct seq_midisynth *msynth;
        struct snd_seq_event ev;
        char buf[16], *pbuf;
        long res;

        if (substream == NULL)
                return;
        runtime = substream->runtime;
        msynth = runtime->private_data;
        if (msynth == NULL)
                return;
        memset(&ev, 0, sizeof(ev));
        while (runtime->avail > 0) {
                res = snd_rawmidi_kernel_read(substream, buf, sizeof(buf));
                if (res <= 0)
                        continue;
                if (msynth->parser == NULL)
                        continue;
                pbuf = buf;
                while (res-- > 0) {
                        if (!snd_midi_event_encode_byte(msynth->parser,
                                                        *pbuf++, &ev))
                                continue;
                        ev.source.port = msynth->seq_port;
                        ev.dest.client = SNDRV_SEQ_ADDRESS_SUBSCRIBERS;
                        snd_seq_kernel_client_dispatch(msynth->seq_client, &ev, 1, 0);
                        /* clear event and reset header */
                        memset(&ev, 0, sizeof(ev));
                }
        }
}

static int dump_midi(struct snd_rawmidi_substream *substream, const char *buf, int count)
{
        struct snd_rawmidi_runtime *runtime;
        int tmp;

        if (snd_BUG_ON(!substream || !buf))
                return -EINVAL;
        runtime = substream->runtime;
        tmp = runtime->avail;
        if (tmp < count) {
                if (printk_ratelimit())
                        pr_err("ALSA: seq_midi: MIDI output buffer overrun\n");
                return -ENOMEM;
        }
        if (snd_rawmidi_kernel_write(substream, buf, count) < count)
                return -EINVAL;
        return 0;
}

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

static int event_process_midi(struct snd_seq_event *ev, int direct,
                              void *private_data, int atomic, int hop)
{
        struct seq_midisynth *msynth = private_data;
        unsigned char msg[10];  /* buffer for constructing midi messages */
        struct snd_rawmidi_substream *substream;
        int len;

        if (snd_BUG_ON(!msynth))
                return -EINVAL;
        substream = msynth->output_rfile.output;
        if (substream == NULL)
                return -ENODEV;
        if (ev->type == SNDRV_SEQ_EVENT_SYSEX) {        /* special case, to save space */
                if ((ev->flags & SNDRV_SEQ_EVENT_LENGTH_MASK) != SNDRV_SEQ_EVENT_LENGTH_VARIABLE) {
                        /* invalid event */
                        pr_debug("ALSA: seq_midi: invalid sysex event flags = 0x%x\n", ev->flags);
                        return 0;
                }
                snd_seq_dump_var_event(ev, __dump_midi, substream);
                snd_midi_event_reset_decode(msynth->parser);
        } else {
                if (msynth->parser == NULL)
                        return -EIO;
                len = snd_midi_event_decode(msynth->parser, msg, sizeof(msg), ev);
                if (len < 0)
                        return 0;
                if (dump_midi(substream, msg, len) < 0)
                        snd_midi_event_reset_decode(msynth->parser);
        }
        return 0;
}


static int snd_seq_midisynth_new(struct seq_midisynth *msynth,
                                 struct snd_card *card,
                                 int device,
                                 int subdevice)
{
        if (snd_midi_event_new(MAX_MIDI_EVENT_BUF, &msynth->parser) < 0)
                return -ENOMEM;
        msynth->card = card;
        msynth->device = device;
        msynth->subdevice = subdevice;
        return 0;
}

/* open associated midi device for input */
static int midisynth_subscribe(void *private_data, struct snd_seq_port_subscribe *info)
{
        int err;
        struct seq_midisynth *msynth = private_data;
        struct snd_rawmidi_runtime *runtime;
        struct snd_rawmidi_params params;

        /* open midi port */
        err = snd_rawmidi_kernel_open(msynth->rmidi, msynth->subdevice,
                                      SNDRV_RAWMIDI_LFLG_INPUT,
                                      &msynth->input_rfile);
        if (err < 0) {
                pr_debug("ALSA: seq_midi: midi input open failed!!!\n");
                return err;
        }
        runtime = msynth->input_rfile.input->runtime;
        memset(&params, 0, sizeof(params));
        params.avail_min = 1;
        params.buffer_size = input_buffer_size;
        err = snd_rawmidi_input_params(msynth->input_rfile.input, &params);
        if (err < 0) {
                snd_rawmidi_kernel_release(&msynth->input_rfile);
                return err;
        }
        snd_midi_event_reset_encode(msynth->parser);
        runtime->event = snd_midi_input_event;
        runtime->private_data = msynth;
        snd_rawmidi_kernel_read(msynth->input_rfile.input, NULL, 0);
        return 0;
}

/* close associated midi device for input */
static int midisynth_unsubscribe(void *private_data, struct snd_seq_port_subscribe *info)
{
        int err;
        struct seq_midisynth *msynth = private_data;

        if (snd_BUG_ON(!msynth->input_rfile.input))
                return -EINVAL;
        err = snd_rawmidi_kernel_release(&msynth->input_rfile);
        return err;
}

/* open associated midi device for output */
static int midisynth_use(void *private_data, struct snd_seq_port_subscribe *info)
{
        int err;
        struct seq_midisynth *msynth = private_data;
        struct snd_rawmidi_params params;

        /* open midi port */
        err = snd_rawmidi_kernel_open(msynth->rmidi, msynth->subdevice,
                                      SNDRV_RAWMIDI_LFLG_OUTPUT,
                                      &msynth->output_rfile);
        if (err < 0) {
                pr_debug("ALSA: seq_midi: midi output open failed!!!\n");
                return err;
        }
        memset(&params, 0, sizeof(params));
        params.avail_min = 1;
        params.buffer_size = output_buffer_size;
        params.no_active_sensing = 1;
        err = snd_rawmidi_output_params(msynth->output_rfile.output, &params);
        if (err < 0) {
                snd_rawmidi_kernel_release(&msynth->output_rfile);
                return err;
        }
        snd_midi_event_reset_decode(msynth->parser);
        return 0;
}

/* close associated midi device for output */
static int midisynth_unuse(void *private_data, struct snd_seq_port_subscribe *info)
{
        struct seq_midisynth *msynth = private_data;

        if (snd_BUG_ON(!msynth->output_rfile.output))
                return -EINVAL;
        snd_rawmidi_drain_output(msynth->output_rfile.output);
        return snd_rawmidi_kernel_release(&msynth->output_rfile);
}

/* delete given midi synth port */
static void snd_seq_midisynth_delete(struct seq_midisynth *msynth)
{
        if (msynth == NULL)
                return;

        if (msynth->seq_client > 0) {
                /* delete port */
                snd_seq_event_port_detach(msynth->seq_client, msynth->seq_port);
        }

        snd_midi_event_free(msynth->parser);
}

/* register new midi synth port */
static int
snd_seq_midisynth_probe(struct snd_seq_device *dev)
{
        struct seq_midisynth_client *client;
        struct seq_midisynth *msynth, *ms;
        struct snd_rawmidi *rmidi = dev->private_data;
        int newclient = 0;
        unsigned int p, ports;
        struct snd_seq_port_callback pcallbacks;
        struct snd_card *card = dev->card;
        int device = dev->device;
        unsigned int input_count = 0, output_count = 0;

        if (snd_BUG_ON(!card || device < 0 || device >= SNDRV_RAWMIDI_DEVICES))
                return -EINVAL;

        struct snd_rawmidi_info *info __free(kfree) =
                kmalloc_obj(*info);
        if (! info)
                return -ENOMEM;
        info->device = device;
        info->stream = SNDRV_RAWMIDI_STREAM_OUTPUT;
        info->subdevice = 0;
        if (snd_rawmidi_info_select(card, info) >= 0)
                output_count = info->subdevices_count;
        info->stream = SNDRV_RAWMIDI_STREAM_INPUT;
        if (snd_rawmidi_info_select(card, info) >= 0) {
                input_count = info->subdevices_count;
        }
        ports = output_count;
        if (ports < input_count)
                ports = input_count;
        if (ports == 0)
                return -ENODEV;
        if (ports > (256 / SNDRV_RAWMIDI_DEVICES))
                ports = 256 / SNDRV_RAWMIDI_DEVICES;

        guard(mutex)(&register_mutex);
        client = synths[card->number];
        if (client == NULL) {
                newclient = 1;
                client = kzalloc_obj(*client);
                if (client == NULL)
                        return -ENOMEM;
                client->seq_client =
                        snd_seq_create_kernel_client(
                                card, 0, "%s", card->shortname[0] ?
                                (const char *)card->shortname : "External MIDI");
                if (client->seq_client < 0) {
                        kfree(client);
                        return -ENOMEM;
                }
        }

        msynth = kzalloc_objs(struct seq_midisynth, ports);

        struct snd_seq_port_info *port __free(kfree) =
                kmalloc_obj(*port);
        if (msynth == NULL || port == NULL)
                goto __nomem;

        for (p = 0; p < ports; p++) {
                ms = &msynth[p];
                ms->rmidi = rmidi;

                if (snd_seq_midisynth_new(ms, card, device, p) < 0)
                        goto __nomem;

                /* declare port */
                memset(port, 0, sizeof(*port));
                port->addr.client = client->seq_client;
                port->addr.port = device * (256 / SNDRV_RAWMIDI_DEVICES) + p;
                port->flags = SNDRV_SEQ_PORT_FLG_GIVEN_PORT;
                memset(info, 0, sizeof(*info));
                info->device = device;
                if (p < output_count)
                        info->stream = SNDRV_RAWMIDI_STREAM_OUTPUT;
                else
                        info->stream = SNDRV_RAWMIDI_STREAM_INPUT;
                info->subdevice = p;
                if (snd_rawmidi_info_select(card, info) >= 0)
                        strscpy(port->name, info->subname);
                if (! port->name[0]) {
                        if (info->name[0]) {
                                if (ports > 1)
                                        scnprintf(port->name, sizeof(port->name), "%s-%u", info->name, p);
                                else
                                        scnprintf(port->name, sizeof(port->name), "%s", info->name);
                        } else {
                                /* last resort */
                                if (ports > 1)
                                        sprintf(port->name, "MIDI %d-%d-%u", card->number, device, p);
                                else
                                        sprintf(port->name, "MIDI %d-%d", card->number, device);
                        }
                }
                if ((info->flags & SNDRV_RAWMIDI_INFO_OUTPUT) && p < output_count)
                        port->capability |= SNDRV_SEQ_PORT_CAP_WRITE | SNDRV_SEQ_PORT_CAP_SYNC_WRITE | SNDRV_SEQ_PORT_CAP_SUBS_WRITE;
                if ((info->flags & SNDRV_RAWMIDI_INFO_INPUT) && p < input_count)
                        port->capability |= SNDRV_SEQ_PORT_CAP_READ | SNDRV_SEQ_PORT_CAP_SYNC_READ | SNDRV_SEQ_PORT_CAP_SUBS_READ;
                if ((port->capability & (SNDRV_SEQ_PORT_CAP_WRITE|SNDRV_SEQ_PORT_CAP_READ)) == (SNDRV_SEQ_PORT_CAP_WRITE|SNDRV_SEQ_PORT_CAP_READ) &&
                    info->flags & SNDRV_RAWMIDI_INFO_DUPLEX)
                        port->capability |= SNDRV_SEQ_PORT_CAP_DUPLEX;
                if (port->capability & SNDRV_SEQ_PORT_CAP_READ)
                        port->direction |= SNDRV_SEQ_PORT_DIR_INPUT;
                if (port->capability & SNDRV_SEQ_PORT_CAP_WRITE)
                        port->direction |= SNDRV_SEQ_PORT_DIR_OUTPUT;
                port->type = SNDRV_SEQ_PORT_TYPE_MIDI_GENERIC
                        | SNDRV_SEQ_PORT_TYPE_HARDWARE
                        | SNDRV_SEQ_PORT_TYPE_PORT;
                port->midi_channels = 16;
                memset(&pcallbacks, 0, sizeof(pcallbacks));
                pcallbacks.owner = THIS_MODULE;
                pcallbacks.private_data = ms;
                pcallbacks.subscribe = midisynth_subscribe;
                pcallbacks.unsubscribe = midisynth_unsubscribe;
                pcallbacks.use = midisynth_use;
                pcallbacks.unuse = midisynth_unuse;
                pcallbacks.event_input = event_process_midi;
                port->kernel = &pcallbacks;
                if (rmidi->ops && rmidi->ops->get_port_info)
                        rmidi->ops->get_port_info(rmidi, p, port);
                if (snd_seq_kernel_client_ctl(client->seq_client, SNDRV_SEQ_IOCTL_CREATE_PORT, port)<0)
                        goto __nomem;
                ms->seq_client = client->seq_client;
                ms->seq_port = port->addr.port;
        }
        client->ports_per_device[device] = ports;
        client->ports[device] = msynth;
        client->num_ports++;
        if (newclient)
                synths[card->number] = client;
        return 0;       /* success */

      __nomem:
        if (msynth != NULL) {
                for (p = 0; p < ports; p++)
                        snd_seq_midisynth_delete(&msynth[p]);
                kfree(msynth);
        }
        if (newclient) {
                snd_seq_delete_kernel_client(client->seq_client);
                kfree(client);
        }
        return -ENOMEM;
}

/* release midi synth port */
static void
snd_seq_midisynth_remove(struct snd_seq_device *dev)
{
        struct seq_midisynth_client *client;
        struct seq_midisynth *msynth;
        struct snd_card *card = dev->card;
        int device = dev->device, p, ports;
        
        guard(mutex)(&register_mutex);
        client = synths[card->number];
        if (client == NULL || client->ports[device] == NULL)
                return;
        ports = client->ports_per_device[device];
        client->ports_per_device[device] = 0;
        msynth = client->ports[device];
        client->ports[device] = NULL;
        for (p = 0; p < ports; p++)
                snd_seq_midisynth_delete(&msynth[p]);
        kfree(msynth);
        client->num_ports--;
        if (client->num_ports <= 0) {
                snd_seq_delete_kernel_client(client->seq_client);
                synths[card->number] = NULL;
                kfree(client);
        }
}

static struct snd_seq_driver seq_midisynth_driver = {
        .probe = snd_seq_midisynth_probe,
        .remove = snd_seq_midisynth_remove,
        .driver = {
                .name = KBUILD_MODNAME,
        },
        .id = SNDRV_SEQ_DEV_ID_MIDISYNTH,
        .argsize = 0,
};

module_snd_seq_driver(seq_midisynth_driver);