/*
   * Stanton Control System 1 MIDI driver
   *
   * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
   * Licensed under the terms of the GNU General Public License, version 2.
   */
  
  #include <linux/device.h>
  #include <linux/firewire.h>
  #include <linux/firewire-constants.h>
  #include <linux/interrupt.h>
  #include <linux/module.h>
  #include <linux/mod_devicetable.h>
  #include <linux/slab.h>
  #include <linux/string.h>
  #include <linux/wait.h>
  #include <sound/core.h>
  #include <sound/initval.h>
  #include <sound/rawmidi.h>
  #include "lib.h"
  
  #define OUI_STANTON	0x001260
  #define MODEL_SCS_1M	0x001000
  #define MODEL_SCS_1D	0x002000
  
  #define HSS1394_ADDRESS			0xc007dedadadaULL
  #define HSS1394_MAX_PACKET_SIZE		64
  
  #define HSS1394_TAG_USER_DATA		0x00
  #define HSS1394_TAG_CHANGE_ADDRESS	0xf1
  
  struct scs {
  	struct snd_card *card;
  	struct fw_unit *unit;
  	struct fw_address_handler hss_handler;
  	struct fw_transaction transaction;
  	bool transaction_running;
  	bool output_idle;
  	u8 output_status;
  	u8 output_bytes;
  	bool output_escaped;
  	bool output_escape_high_nibble;
  	u8 input_escape_count;
  	struct snd_rawmidi_substream *output;
  	struct snd_rawmidi_substream *input;
  	struct tasklet_struct tasklet;
  	wait_queue_head_t idle_wait;
  	u8 *buffer;
  };
  
  static const u8 sysex_escape_prefix[] = {
  	0xf0,			/* SysEx begin */
  	0x00, 0x01, 0x60,	/* Stanton DJ */
  	0x48, 0x53, 0x53,	/* "HSS" */
  };
  
  static int scs_output_open(struct snd_rawmidi_substream *stream)
  {
  	struct scs *scs = stream->rmidi->private_data;
  
  	scs->output_status = 0;
  	scs->output_bytes = 1;
  	scs->output_escaped = false;
  
  	return 0;
  }
  
  static int scs_output_close(struct snd_rawmidi_substream *stream)
  {
  	return 0;
  }
  
  static void scs_output_trigger(struct snd_rawmidi_substream *stream, int up)
  {
  	struct scs *scs = stream->rmidi->private_data;
  
  	ACCESS_ONCE(scs->output) = up ? stream : NULL;
  	if (up) {
  		scs->output_idle = false;
  		tasklet_schedule(&scs->tasklet);
  	}
  }
  
  static void scs_write_callback(struct fw_card *card, int rcode,
  			       void *data, size_t length, void *callback_data)
  {
  	struct scs *scs = callback_data;
  
  	if (rcode == RCODE_GENERATION) {
  		/* TODO: retry this packet */
  	}
  
  	scs->transaction_running = false;
  	tasklet_schedule(&scs->tasklet);
  }
  
  static bool is_valid_running_status(u8 status)
  {
  	return status >= 0x80 && status <= 0xef;
  }
  
  static bool is_one_byte_cmd(u8 status)
  {
  	return status == 0xf6 ||
  	       status >= 0xf8;
  }
  
  static bool is_two_bytes_cmd(u8 status)
  {
  	return (status >= 0xc0 && status <= 0xdf) ||
  	       status == 0xf1 ||
  	       status == 0xf3;
  }
  
  static bool is_three_bytes_cmd(u8 status)
  {
  	return (status >= 0x80 && status <= 0xbf) ||
  	       (status >= 0xe0 && status <= 0xef) ||
  	       status == 0xf2;
  }
  
  static bool is_invalid_cmd(u8 status)
  {
  	return status == 0xf4 ||
  	       status == 0xf5 ||
  	       status == 0xf9 ||
  	       status == 0xfd;
  }
  
  static void scs_output_tasklet(unsigned long data)
  {
  	struct scs *scs = (void *)data;
  	struct snd_rawmidi_substream *stream;
  	unsigned int i;
  	u8 byte;
  	struct fw_device *dev;
  	int generation;
  
  	if (scs->transaction_running)
  		return;
  
  	stream = ACCESS_ONCE(scs->output);
  	if (!stream) {
  		scs->output_idle = true;
  		wake_up(&scs->idle_wait);
  		return;
  	}
  
  	i = scs->output_bytes;
  	for (;;) {
  		if (snd_rawmidi_transmit(stream, &byte, 1) != 1) {
  			scs->output_bytes = i;
  			scs->output_idle = true;
  			wake_up(&scs->idle_wait);
  			return;
  		}
  		/*
  		 * Convert from real MIDI to what I think the device expects (no
  		 * running status, one command per packet, unescaped SysExs).
  		 */
  		if (scs->output_escaped && byte < 0x80) {
  			if (scs->output_escape_high_nibble) {
  				if (i < HSS1394_MAX_PACKET_SIZE) {
  					scs->buffer[i] = byte << 4;
  					scs->output_escape_high_nibble = false;
  				}
  			} else {
  				scs->buffer[i++] |= byte & 0x0f;
  				scs->output_escape_high_nibble = true;
  			}
  		} else if (byte < 0x80) {
  			if (i == 1) {
  				if (!is_valid_running_status(scs->output_status))
  					continue;
  				scs->buffer[0] = HSS1394_TAG_USER_DATA;
  				scs->buffer[i++] = scs->output_status;
  			}
  			scs->buffer[i++] = byte;
  			if ((i == 3 && is_two_bytes_cmd(scs->output_status)) ||
  			    (i == 4 && is_three_bytes_cmd(scs->output_status)))
  				break;
  			if (i == 1 + ARRAY_SIZE(sysex_escape_prefix) &&
  			    !memcmp(scs->buffer + 1, sysex_escape_prefix,
  				    ARRAY_SIZE(sysex_escape_prefix))) {
  				scs->output_escaped = true;
  				scs->output_escape_high_nibble = true;
  				i = 0;
  			}
  			if (i >= HSS1394_MAX_PACKET_SIZE)
  				i = 1;
  		} else if (byte == 0xf7) {
  			if (scs->output_escaped) {
  				if (i >= 1 && scs->output_escape_high_nibble &&
  				    scs->buffer[0] != HSS1394_TAG_CHANGE_ADDRESS)
  					break;
  			} else {
  				if (i > 1 && scs->output_status == 0xf0) {
  					scs->buffer[i++] = 0xf7;
  					break;
  				}
  			}
  			i = 1;
  			scs->output_escaped = false;
  		} else if (!is_invalid_cmd(byte) &&
  			   byte < 0xf8) {
  			i = 1;
  			scs->buffer[0] = HSS1394_TAG_USER_DATA;
  			scs->buffer[i++] = byte;
  			scs->output_status = byte;
  			scs->output_escaped = false;
  			if (is_one_byte_cmd(byte))
  				break;
  		}
  	}
  	scs->output_bytes = 1;
  	scs->output_escaped = false;
  
  	scs->transaction_running = true;
  	dev = fw_parent_device(scs->unit);
  	generation = dev->generation;
  	smp_rmb(); /* node_id vs. generation */
  	fw_send_request(dev->card, &scs->transaction, TCODE_WRITE_BLOCK_REQUEST,
  			dev->node_id, generation, dev->max_speed,
  			HSS1394_ADDRESS, scs->buffer, i,
  			scs_write_callback, scs);
  }
  
  static void scs_output_drain(struct snd_rawmidi_substream *stream)
  {
  	struct scs *scs = stream->rmidi->private_data;
  
  	wait_event(scs->idle_wait, scs->output_idle);
  }
  
  static struct snd_rawmidi_ops output_ops = {
  	.open    = scs_output_open,
  	.close   = scs_output_close,
  	.trigger = scs_output_trigger,
  	.drain   = scs_output_drain,
  };
  
  static int scs_input_open(struct snd_rawmidi_substream *stream)
  {
  	struct scs *scs = stream->rmidi->private_data;
  
  	scs->input_escape_count = 0;
  
  	return 0;
  }
  
  static int scs_input_close(struct snd_rawmidi_substream *stream)
  {
  	return 0;
  }
  
  static void scs_input_trigger(struct snd_rawmidi_substream *stream, int up)
  {
  	struct scs *scs = stream->rmidi->private_data;
  
  	ACCESS_ONCE(scs->input) = up ? stream : NULL;
  }
  
  static void scs_input_escaped_byte(struct snd_rawmidi_substream *stream,
  				   u8 byte)
  {
  	u8 nibbles[2];
  
  	nibbles[0] = byte >> 4;
  	nibbles[1] = byte & 0x0f;
  	snd_rawmidi_receive(stream, nibbles, 2);
  }
  
  static void scs_input_midi_byte(struct scs *scs,
  				struct snd_rawmidi_substream *stream,
  				u8 byte)
  {
  	if (scs->input_escape_count > 0) {
  		scs_input_escaped_byte(stream, byte);
  		scs->input_escape_count--;
  		if (scs->input_escape_count == 0)
  			snd_rawmidi_receive(stream, (const u8[]) { 0xf7 }, 1);
  	} else if (byte == 0xf9) {
  		snd_rawmidi_receive(stream, sysex_escape_prefix,
  				    ARRAY_SIZE(sysex_escape_prefix));
  		scs_input_escaped_byte(stream, 0x00);
  		scs_input_escaped_byte(stream, 0xf9);
  		scs->input_escape_count = 3;
  	} else {
  		snd_rawmidi_receive(stream, &byte, 1);
  	}
  }
  
  static void scs_input_packet(struct scs *scs,
  			     struct snd_rawmidi_substream *stream,
  			     const u8 *data, unsigned int bytes)
  {
  	unsigned int i;
  
  	if (data[0] == HSS1394_TAG_USER_DATA) {
  		for (i = 1; i < bytes; ++i)
  			scs_input_midi_byte(scs, stream, data[i]);
  	} else {
  		snd_rawmidi_receive(stream, sysex_escape_prefix,
  				    ARRAY_SIZE(sysex_escape_prefix));
  		for (i = 0; i < bytes; ++i)
  			scs_input_escaped_byte(stream, data[i]);
  		snd_rawmidi_receive(stream, (const u8[]) { 0xf7 }, 1);
  	}
  }
  
  static struct snd_rawmidi_ops input_ops = {
  	.open    = scs_input_open,
  	.close   = scs_input_close,
  	.trigger = scs_input_trigger,
  };
  
  static int scs_create_midi(struct scs *scs)
  {
  	struct snd_rawmidi *rmidi;
  	int err;
  
  	err = snd_rawmidi_new(scs->card, "SCS.1x", 0, 1, 1, &rmidi);
  	if (err < 0)
  		return err;
  	snprintf(rmidi->name, sizeof(rmidi->name),
  		 "%s MIDI", scs->card->shortname);
  	rmidi->info_flags = SNDRV_RAWMIDI_INFO_OUTPUT |
  	                    SNDRV_RAWMIDI_INFO_INPUT |
  	                    SNDRV_RAWMIDI_INFO_DUPLEX;
  	rmidi->private_data = scs;
  	snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_OUTPUT, &output_ops);
  	snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_INPUT, &input_ops);
  
  	return 0;
  }
  
  static void handle_hss(struct fw_card *card, struct fw_request *request,
  		       int tcode, int destination, int source, int generation,
  		       unsigned long long offset, void *data, size_t length,
  		       void *callback_data)
  {
  	struct scs *scs = callback_data;
  	struct snd_rawmidi_substream *stream;
  
  	if (offset != scs->hss_handler.offset) {
  		fw_send_response(card, request, RCODE_ADDRESS_ERROR);
  		return;
  	}
  	if (tcode != TCODE_WRITE_QUADLET_REQUEST &&
  	    tcode != TCODE_WRITE_BLOCK_REQUEST) {
  		fw_send_response(card, request, RCODE_TYPE_ERROR);
  		return;
  	}
  
  	if (length >= 1) {
  		stream = ACCESS_ONCE(scs->input);
  		if (stream)
  			scs_input_packet(scs, stream, data, length);
  	}
  
  	fw_send_response(card, request, RCODE_COMPLETE);
  }
  
  static int scs_init_hss_address(struct scs *scs)
  {
  	__be64 data;
  	int err;
  
  	data = cpu_to_be64(((u64)HSS1394_TAG_CHANGE_ADDRESS << 56) |
  			   scs->hss_handler.offset);
  	err = snd_fw_transaction(scs->unit, TCODE_WRITE_BLOCK_REQUEST,
  				 HSS1394_ADDRESS, &data, 8, 0);
  	if (err < 0)
  		dev_err(&scs->unit->device, "HSS1394 communication failed
  ");
  
  	return err;
  }
  
  static void scs_card_free(struct snd_card *card)
  {
  	struct scs *scs = card->private_data;
  
  	fw_core_remove_address_handler(&scs->hss_handler);
  	kfree(scs->buffer);
  }
  
  static int scs_probe(struct fw_unit *unit, const struct ieee1394_device_id *id)
  {
  	struct fw_device *fw_dev = fw_parent_device(unit);
  	struct snd_card *card;
  	struct scs *scs;
  	int err;
  
  	err = snd_card_create(-16, NULL, THIS_MODULE, sizeof(*scs), &card);
  	if (err < 0)
  		return err;
  	snd_card_set_dev(card, &unit->device);
  
  	scs = card->private_data;
  	scs->card = card;
  	scs->unit = unit;
  	tasklet_init(&scs->tasklet, scs_output_tasklet, (unsigned long)scs);
  	init_waitqueue_head(&scs->idle_wait);
  	scs->output_idle = true;
  
  	scs->buffer = kmalloc(HSS1394_MAX_PACKET_SIZE, GFP_KERNEL);
  	if (!scs->buffer) {
  		err = -ENOMEM;
  		goto err_card;
  	}
  
  	scs->hss_handler.length = HSS1394_MAX_PACKET_SIZE;
  	scs->hss_handler.address_callback = handle_hss;
  	scs->hss_handler.callback_data = scs;
  	err = fw_core_add_address_handler(&scs->hss_handler,
  					  &fw_high_memory_region);
  	if (err < 0)
  		goto err_buffer;
  
  	card->private_free = scs_card_free;
  
  	strcpy(card->driver, "SCS.1x");
  	strcpy(card->shortname, "SCS.1x");
  	fw_csr_string(unit->directory, CSR_MODEL,
  		      card->shortname, sizeof(card->shortname));
  	snprintf(card->longname, sizeof(card->longname),
  		 "Stanton DJ %s (GUID %08x%08x) at %s, S%d",
  		 card->shortname, fw_dev->config_rom[3], fw_dev->config_rom[4],
  		 dev_name(&unit->device), 100 << fw_dev->max_speed);
  	strcpy(card->mixername, card->shortname);
  
  	err = scs_init_hss_address(scs);
  	if (err < 0)
  		goto err_card;
  
  	err = scs_create_midi(scs);
  	if (err < 0)
  		goto err_card;
  
  	err = snd_card_register(card);
  	if (err < 0)
  		goto err_card;
  
  	dev_set_drvdata(&unit->device, scs);
  
  	return 0;
  
  err_buffer:
  	kfree(scs->buffer);
  err_card:
  	snd_card_free(card);
  	return err;
  }
  
  static void scs_update(struct fw_unit *unit)
  {
  	struct scs *scs = dev_get_drvdata(&unit->device);
  	int generation;
  	__be64 data;
  
  	data = cpu_to_be64(((u64)HSS1394_TAG_CHANGE_ADDRESS << 56) |
  			   scs->hss_handler.offset);
  	generation = fw_parent_device(unit)->generation;
  	smp_rmb(); /* node_id vs. generation */
  	snd_fw_transaction(scs->unit, TCODE_WRITE_BLOCK_REQUEST,
  			   HSS1394_ADDRESS, &data, 8,
  			   FW_FIXED_GENERATION | generation);
  }
  
  static void scs_remove(struct fw_unit *unit)
  {
  	struct scs *scs = dev_get_drvdata(&unit->device);
  
  	snd_card_disconnect(scs->card);
  
  	ACCESS_ONCE(scs->output) = NULL;
  	ACCESS_ONCE(scs->input) = NULL;
  
  	wait_event(scs->idle_wait, scs->output_idle);
  
  	tasklet_kill(&scs->tasklet);
  
  	snd_card_free_when_closed(scs->card);
  }
  
  static const struct ieee1394_device_id scs_id_table[] = {
  	{
  		.match_flags = IEEE1394_MATCH_VENDOR_ID |
  		               IEEE1394_MATCH_MODEL_ID,
  		.vendor_id   = OUI_STANTON,
  		.model_id    = MODEL_SCS_1M,
  	},
  	{
  		.match_flags = IEEE1394_MATCH_VENDOR_ID |
  		               IEEE1394_MATCH_MODEL_ID,
  		.vendor_id   = OUI_STANTON,
  		.model_id    = MODEL_SCS_1D,
  	},
  	{}
  };
  MODULE_DEVICE_TABLE(ieee1394, scs_id_table);
  
  MODULE_DESCRIPTION("SCS.1x MIDI driver");
  MODULE_AUTHOR("Clemens Ladisch <clemens@ladisch.de>");
  MODULE_LICENSE("GPL v2");
  
  static struct fw_driver scs_driver = {
  	.driver = {
  		.owner  = THIS_MODULE,
  		.name   = KBUILD_MODNAME,
  		.bus    = &fw_bus_type,
  	},
  	.probe    = scs_probe,
  	.update   = scs_update,
  	.remove   = scs_remove,
  	.id_table = scs_id_table,
  };
  
  static int __init alsa_scs1x_init(void)
  {
  	return driver_register(&scs_driver.driver);
  }
  
  static void __exit alsa_scs1x_exit(void)
  {
  	driver_unregister(&scs_driver.driver);
  }
  
  module_init(alsa_scs1x_init);
  module_exit(alsa_scs1x_exit);