serial-generic.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *   serial-generic.c
 *   Copyright (c) by Daniel Kaehn <[email protected]
 *   Based on serial-u16550.c by Jaroslav Kysela <[email protected]>,
 *		                 Isaku Yamahata <[email protected]>,
 *		                 George Hansper <[email protected]>,
 *		                 Hannu Savolainen
 *
 * Generic serial MIDI driver using the serdev serial bus API for hardware interaction
 */

#include <linux/err.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/serdev.h>
#include <linux/serial_reg.h>
#include <linux/slab.h>
#include <linux/dev_printk.h>

#include <sound/core.h>
#include <sound/rawmidi.h>
#include <sound/initval.h>

MODULE_DESCRIPTION("Generic serial MIDI driver");
MODULE_LICENSE("GPL");

#define SERIAL_MODE_INPUT_OPEN		1
#define SERIAL_MODE_OUTPUT_OPEN	2
#define SERIAL_MODE_INPUT_TRIGGERED	3
#define SERIAL_MODE_OUTPUT_TRIGGERED	4

#define SERIAL_TX_STATE_ACTIVE	1
#define SERIAL_TX_STATE_WAKEUP	2

struct snd_serial_generic {
	struct serdev_device *serdev;

	struct snd_card *card;
	struct snd_rawmidi *rmidi;
	struct snd_rawmidi_substream *midi_output;
	struct snd_rawmidi_substream *midi_input;

	unsigned int baudrate;

	unsigned long filemode;		/* open status of file */
	struct work_struct tx_work;
	unsigned long tx_state;

};

static void snd_serial_generic_tx_wakeup(struct snd_serial_generic *drvdata)
{
	if (test_and_set_bit(SERIAL_TX_STATE_ACTIVE, &drvdata->tx_state))
		set_bit(SERIAL_TX_STATE_WAKEUP, &drvdata->tx_state);

	schedule_work(&drvdata->tx_work);
}

#define INTERNAL_BUF_SIZE 256

static void snd_serial_generic_tx_work(struct work_struct *work)
{
	static char buf[INTERNAL_BUF_SIZE];
	int num_bytes;
	struct snd_serial_generic *drvdata = container_of(work, struct snd_serial_generic,
						   tx_work);
	struct snd_rawmidi_substream *substream = drvdata->midi_output;

	clear_bit(SERIAL_TX_STATE_WAKEUP, &drvdata->tx_state);

	while (!snd_rawmidi_transmit_empty(substream)) {

		if (!test_bit(SERIAL_MODE_OUTPUT_OPEN, &drvdata->filemode))
			break;

		num_bytes = snd_rawmidi_transmit_peek(substream, buf, INTERNAL_BUF_SIZE);
		num_bytes = serdev_device_write_buf(drvdata->serdev, buf, num_bytes);

		if (!num_bytes)
			break;

		snd_rawmidi_transmit_ack(substream, num_bytes);

		if (!test_bit(SERIAL_TX_STATE_WAKEUP, &drvdata->tx_state))
			break;
	}

	clear_bit(SERIAL_TX_STATE_ACTIVE, &drvdata->tx_state);
}

static void snd_serial_generic_write_wakeup(struct serdev_device *serdev)
{
	struct snd_serial_generic *drvdata = serdev_device_get_drvdata(serdev);

	snd_serial_generic_tx_wakeup(drvdata);
}

static size_t snd_serial_generic_receive_buf(struct serdev_device *serdev,
					     const u8 *buf, size_t count)
{
	int ret;
	struct snd_serial_generic *drvdata = serdev_device_get_drvdata(serdev);

	if (!test_bit(SERIAL_MODE_INPUT_OPEN, &drvdata->filemode))
		return 0;

	ret = snd_rawmidi_receive(drvdata->midi_input, buf, count);
	return ret < 0 ? 0 : ret;
}

static const struct serdev_device_ops snd_serial_generic_serdev_device_ops = {
	.receive_buf = snd_serial_generic_receive_buf,
	.write_wakeup = snd_serial_generic_write_wakeup
};

static int snd_serial_generic_ensure_serdev_open(struct snd_serial_generic *drvdata)
{
	int err;
	unsigned int actual_baud;

	if (drvdata->filemode)
		return 0;

	dev_dbg(drvdata->card->dev, "Opening serial port for card %s\n",
		drvdata->card->shortname);
	err = serdev_device_open(drvdata->serdev);
	if (err < 0)
		return err;

	actual_baud = serdev_device_set_baudrate(drvdata->serdev,
		drvdata->baudrate);
	if (actual_baud != drvdata->baudrate) {
		dev_warn(drvdata->card->dev, "requested %d baud for card %s but it was actually set to %d\n",
			drvdata->baudrate, drvdata->card->shortname, actual_baud);
	}

	return 0;
}

static int snd_serial_generic_input_open(struct snd_rawmidi_substream *substream)
{
	int err;
	struct snd_serial_generic *drvdata = substream->rmidi->card->private_data;

	dev_dbg(drvdata->card->dev, "Opening input for card %s\n",
		drvdata->card->shortname);

	err = snd_serial_generic_ensure_serdev_open(drvdata);
	if (err < 0)
		return err;

	set_bit(SERIAL_MODE_INPUT_OPEN, &drvdata->filemode);
	drvdata->midi_input = substream;
	return 0;
}

static int snd_serial_generic_input_close(struct snd_rawmidi_substream *substream)
{
	struct snd_serial_generic *drvdata = substream->rmidi->card->private_data;

	dev_dbg(drvdata->card->dev, "Closing input for card %s\n",
		drvdata->card->shortname);

	clear_bit(SERIAL_MODE_INPUT_OPEN, &drvdata->filemode);
	clear_bit(SERIAL_MODE_INPUT_TRIGGERED, &drvdata->filemode);

	drvdata->midi_input = NULL;

	if (!drvdata->filemode)
		serdev_device_close(drvdata->serdev);
	return 0;
}

static void snd_serial_generic_input_trigger(struct snd_rawmidi_substream *substream,
					int up)
{
	struct snd_serial_generic *drvdata = substream->rmidi->card->private_data;

	if (up)
		set_bit(SERIAL_MODE_INPUT_TRIGGERED, &drvdata->filemode);
	else
		clear_bit(SERIAL_MODE_INPUT_TRIGGERED, &drvdata->filemode);
}

static int snd_serial_generic_output_open(struct snd_rawmidi_substream *substream)
{
	struct snd_serial_generic *drvdata = substream->rmidi->card->private_data;
	int err;

	dev_dbg(drvdata->card->dev, "Opening output for card %s\n",
		drvdata->card->shortname);

	err = snd_serial_generic_ensure_serdev_open(drvdata);
	if (err < 0)
		return err;

	set_bit(SERIAL_MODE_OUTPUT_OPEN, &drvdata->filemode);

	drvdata->midi_output = substream;
	return 0;
};

static int snd_serial_generic_output_close(struct snd_rawmidi_substream *substream)
{
	struct snd_serial_generic *drvdata = substream->rmidi->card->private_data;

	dev_dbg(drvdata->card->dev, "Closing output for card %s\n",
		drvdata->card->shortname);

	clear_bit(SERIAL_MODE_OUTPUT_OPEN, &drvdata->filemode);
	clear_bit(SERIAL_MODE_OUTPUT_TRIGGERED, &drvdata->filemode);

	if (!drvdata->filemode)
		serdev_device_close(drvdata->serdev);

	drvdata->midi_output = NULL;

	return 0;
};

static void snd_serial_generic_output_trigger(struct snd_rawmidi_substream *substream,
					 int up)
{
	struct snd_serial_generic *drvdata = substream->rmidi->card->private_data;

	if (up)
		set_bit(SERIAL_MODE_OUTPUT_TRIGGERED, &drvdata->filemode);
	else
		clear_bit(SERIAL_MODE_OUTPUT_TRIGGERED, &drvdata->filemode);

	if (up)
		snd_serial_generic_tx_wakeup(drvdata);
}

static void snd_serial_generic_output_drain(struct snd_rawmidi_substream *substream)
{
	struct snd_serial_generic *drvdata = substream->rmidi->card->private_data;

	/* Flush any pending characters */
	serdev_device_write_flush(drvdata->serdev);
	cancel_work_sync(&drvdata->tx_work);
}

static const struct snd_rawmidi_ops snd_serial_generic_output = {
	.open =		snd_serial_generic_output_open,
	.close =	snd_serial_generic_output_close,
	.trigger =	snd_serial_generic_output_trigger,
	.drain =	snd_serial_generic_output_drain,
};

static const struct snd_rawmidi_ops snd_serial_generic_input = {
	.open =		snd_serial_generic_input_open,
	.close =	snd_serial_generic_input_close,
	.trigger =	snd_serial_generic_input_trigger,
};

static void snd_serial_generic_parse_dt(struct serdev_device *serdev,
				struct snd_serial_generic *drvdata)
{
	int err;

	err = of_property_read_u32(serdev->dev.of_node, "current-speed",
		&drvdata->baudrate);
	if (err < 0) {
		dev_dbg(drvdata->card->dev,
			"MIDI device reading of current-speed DT param failed with error %d, using default of 38400\n",
			err);
		drvdata->baudrate = 38400;
	}

}

static void snd_serial_generic_substreams(struct snd_rawmidi_str *stream, int dev_num)
{
	struct snd_rawmidi_substream *substream;

	list_for_each_entry(substream, &stream->substreams, list) {
		sprintf(substream->name, "Serial MIDI %d-%d", dev_num, substream->number);
	}
}

static int snd_serial_generic_rmidi(struct snd_serial_generic *drvdata,
				int outs, int ins, struct snd_rawmidi **rmidi)
{
	struct snd_rawmidi *rrawmidi;
	int err;

	err = snd_rawmidi_new(drvdata->card, drvdata->card->driver, 0,
				outs, ins, &rrawmidi);

	if (err < 0)
		return err;

	snd_rawmidi_set_ops(rrawmidi, SNDRV_RAWMIDI_STREAM_INPUT,
				&snd_serial_generic_input);
	snd_rawmidi_set_ops(rrawmidi, SNDRV_RAWMIDI_STREAM_OUTPUT,
				&snd_serial_generic_output);
	strscpy(rrawmidi->name, drvdata->card->shortname);

	snd_serial_generic_substreams(&rrawmidi->streams[SNDRV_RAWMIDI_STREAM_OUTPUT],
					drvdata->serdev->ctrl->nr);
	snd_serial_generic_substreams(&rrawmidi->streams[SNDRV_RAWMIDI_STREAM_INPUT],
					drvdata->serdev->ctrl->nr);

	rrawmidi->info_flags = SNDRV_RAWMIDI_INFO_OUTPUT |
			       SNDRV_RAWMIDI_INFO_INPUT |
			       SNDRV_RAWMIDI_INFO_DUPLEX;

	if (rmidi)
		*rmidi = rrawmidi;
	return 0;
}

static int snd_serial_generic_probe(struct serdev_device *serdev)
{
	struct snd_card *card;
	struct snd_serial_generic *drvdata;
	int err;

	err  = snd_devm_card_new(&serdev->dev, SNDRV_DEFAULT_IDX1,
				SNDRV_DEFAULT_STR1, THIS_MODULE,
				sizeof(struct snd_serial_generic), &card);

	if (err < 0)
		return err;

	strscpy(card->driver, "SerialMIDI");
	sprintf(card->shortname, "SerialMIDI-%d", serdev->ctrl->nr);
	sprintf(card->longname, "Serial MIDI device at serial%d", serdev->ctrl->nr);

	drvdata = card->private_data;

	drvdata->serdev = serdev;
	drvdata->card = card;

	snd_serial_generic_parse_dt(serdev, drvdata);

	INIT_WORK(&drvdata->tx_work, snd_serial_generic_tx_work);

	err = snd_serial_generic_rmidi(drvdata, 1, 1, &drvdata->rmidi);
	if (err < 0)
		return err;

	serdev_device_set_client_ops(serdev, &snd_serial_generic_serdev_device_ops);
	serdev_device_set_drvdata(drvdata->serdev, drvdata);

	err = snd_card_register(card);
	if (err < 0)
		return err;

	return 0;
}

static const struct of_device_id snd_serial_generic_dt_ids[] = {
	{ .compatible = "serial-midi" },
	{},
};

MODULE_DEVICE_TABLE(of, snd_serial_generic_dt_ids);

static struct serdev_device_driver snd_serial_generic_driver = {
	.driver	= {
		.name		= "snd-serial-generic",
		.of_match_table	= snd_serial_generic_dt_ids,
	},
	.probe	= snd_serial_generic_probe,
};

module_serdev_device_driver(snd_serial_generic_driver);