Generic serial MIDI driver adding support for using serial devices
compatible with the serial bus as raw MIDI devices, allowing using
additional serial devices not compatible with the existing
serial-u16550 driver. Supports only setting standard serial baudrates on
the underlying serial device; however, the underlying serial device can
be configured so that a requested 38.4 kBaud is actually the standard MIDI
31.25 kBaud. Supports DeviceTree configuration.
Signed-off-by: Daniel Kaehn <kaehndan@xxxxxxxxx>
---
sound/drivers/Kconfig | 18 ++
sound/drivers/Makefile | 2 +
sound/drivers/serial-generic.c | 374 +++++++++++++++++++++++++++++++++
3 files changed, 394 insertions(+)
create mode 100644 sound/drivers/serial-generic.c
diff --git a/sound/drivers/Kconfig b/sound/drivers/Kconfig
index ca4cdf666f82..be3009746f3a 100644
--- a/sound/drivers/Kconfig
+++ b/sound/drivers/Kconfig
@@ -165,6 +165,24 @@ config SND_SERIAL_U16550
To compile this driver as a module, choose M here: the module
will be called snd-serial-u16550.
+config SND_SERIAL_GENERIC
+ tristate "Generic serial MIDI driver"
+ depends on SERIAL_DEV_BUS
+ depends on OF
+ select SND_RAWMIDI
+ help
+ To include support for mapping generic serial devices as raw
+ ALSA MIDI devices, say Y here. The driver only supports setting
+ the serial port to standard baudrates. To attain the standard MIDI
+ baudrate of 31.25 kBaud, configure the clock of the underlying serial
+ device so that a requested 38.4 kBaud will result in the standard speed.
+
+ Use this devicetree binding to configure serial port mapping
+ <file:Documentation/devicetree/bindings/sound/serial-midi.yaml>
+
+ To compile this driver as a module, choose M here: the module
+ will be called snd-serial-generic.
+
config SND_MPU401
tristate "Generic MPU-401 UART driver"
select SND_MPU401_UART
diff --git a/sound/drivers/Makefile b/sound/drivers/Makefile
index c0fe4eccdaef..b60303180a1b 100644
--- a/sound/drivers/Makefile
+++ b/sound/drivers/Makefile
@@ -10,6 +10,7 @@ snd-mtpav-objs := mtpav.o
snd-mts64-objs := mts64.o
snd-portman2x4-objs := portman2x4.o
snd-serial-u16550-objs := serial-u16550.o
+snd-serial-generic-objs := serial-generic.o
snd-virmidi-objs := virmidi.o
# Toplevel Module Dependency
@@ -17,6 +18,7 @@ obj-$(CONFIG_SND_DUMMY) += snd-dummy.o
obj-$(CONFIG_SND_ALOOP) += snd-aloop.o
obj-$(CONFIG_SND_VIRMIDI) += snd-virmidi.o
obj-$(CONFIG_SND_SERIAL_U16550) += snd-serial-u16550.o
+obj-$(CONFIG_SND_SERIAL_GENERIC) += snd-serial-generic.o
obj-$(CONFIG_SND_MTPAV) += snd-mtpav.o
obj-$(CONFIG_SND_MTS64) += snd-mts64.o
obj-$(CONFIG_SND_PORTMAN2X4) += snd-portman2x4.o
diff --git a/sound/drivers/serial-generic.c b/sound/drivers/serial-generic.c
new file mode 100644
index 000000000000..e1f864dc7939
--- /dev/null
+++ b/sound/drivers/serial-generic.c
@@ -0,0 +1,374 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * serial-generic.c
+ * Copyright (c) by Daniel Kaehn <kaehndan@xxxxxxxxx
+ * Based on serial-u16550.c by Jaroslav Kysela <perex@xxxxxxxx>,
+ * Isaku Yamahata <yamahata@xxxxxxxxxxxxxxxxxxx>,
+ * George Hansper <ghansper@xxxxxxxxxxxx>,
+ * 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_device.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 int snd_serial_generic_receive_buf(struct serdev_device *serdev,
+ const unsigned char *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);
+ strcpy(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;
+
+ strcpy(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 = of_match_ptr(snd_serial_generic_dt_ids),
+ },
+ .probe = snd_serial_generic_probe,
+};
+
+module_serdev_device_driver(snd_serial_generic_driver);
--
2.33.0
