ALSA: usb-audio: add Starr Labs USB MIDI support

Add support for Starr Labs USB MIDI devices such as the Z7S, which are
based on an FTDI serial UART chip.

Based on a patch by Daniel Mack.

Signed-off-by: Kristian Amlie <kristian@amlie.name>
Acked-by: Daniel Mack <zonque@gmail.com>
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

4 files changed, 40 insertions, 0 deletions

diff --git a/sound/usb/midi.c b/sound/usb/midi.c
index f9289102886a..e21f026d9577 100644
--- a/sound/usb/midi.c
+++ b/sound/usb/midi.c
@@ -816,6 +816,22 @@ static struct usb_protocol_ops snd_usbmidi_raw_ops = {
         .output = snd_usbmidi_raw_output,
 };
 
+/*
+ * FTDI protocol: raw MIDI bytes, but input packets have two modem status bytes.
+ */
+
+static void snd_usbmidi_ftdi_input(struct snd_usb_midi_in_endpoint* ep,
+                                   uint8_t* buffer, int buffer_length)
+{
+        if (buffer_length > 2)
+                snd_usbmidi_input_data(ep, 0, buffer + 2, buffer_length - 2);
+}
+
+static struct usb_protocol_ops snd_usbmidi_ftdi_ops = {
+        .input = snd_usbmidi_ftdi_input,
+        .output = snd_usbmidi_raw_output,
+};
+
 static void snd_usbmidi_us122l_input(struct snd_usb_midi_in_endpoint *ep,
                                      uint8_t *buffer, int buffer_length)
 {
@@ -2163,6 +2179,17 @@ int snd_usbmidi_create(struct snd_card *card,
                 /* endpoint 1 is input-only */
                 endpoints[1].out_cables = 0;
                 break;
+        case QUIRK_MIDI_FTDI:
+                umidi->usb_protocol_ops = &snd_usbmidi_ftdi_ops;
+
+                /* set baud rate to 31250 (48 MHz / 16 / 96) */
+                err = usb_control_msg(umidi->dev, usb_sndctrlpipe(umidi->dev, 0),
+                                      3, 0x40, 0x60, 0, NULL, 0, 1000);
+                if (err < 0)
+                        break;
+
+                err = snd_usbmidi_detect_per_port_endpoints(umidi, endpoints);
+                break;
         default:
                 snd_printd(KERN_ERR "invalid quirk type %d\n", quirk->type);
                 err = -ENXIO;
diff --git a/sound/usb/quirks-table.h b/sound/usb/quirks-table.h
index a42e3ef3832d..da898229bb11 100644
--- a/sound/usb/quirks-table.h
+++ b/sound/usb/quirks-table.h
@@ -39,6 +39,17 @@
         .idProduct = prod, \
         .bInterfaceClass = USB_CLASS_VENDOR_SPEC
 
+/* FTDI devices */
+{
+        USB_DEVICE(0x0403, 0xb8d8),
+        .driver_info = (unsigned long) & (const struct snd_usb_audio_quirk) {
+                /* .vendor_name = "STARR LABS", */
+                /* .product_name = "Starr Labs MIDI USB device", */
+                .ifnum = 0,
+                .type = QUIRK_MIDI_FTDI
+        }
+},
+
 /* Creative/Toshiba Multimedia Center SB-0500 */
 {
         USB_DEVICE(0x041e, 0x3048),
diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c
index 81e07d842581..cf61b0340026 100644
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -306,6 +306,7 @@ int snd_usb_create_quirk(struct snd_usb_audio *chip,
                 [QUIRK_MIDI_EMAGIC] = create_any_midi_quirk,
                 [QUIRK_MIDI_CME] = create_any_midi_quirk,
                 [QUIRK_MIDI_AKAI] = create_any_midi_quirk,
+                [QUIRK_MIDI_FTDI] = create_any_midi_quirk,
                 [QUIRK_AUDIO_STANDARD_INTERFACE] = create_standard_audio_quirk,
                 [QUIRK_AUDIO_FIXED_ENDPOINT] = create_fixed_stream_quirk,
                 [QUIRK_AUDIO_EDIROL_UAXX] = create_uaxx_quirk,
diff --git a/sound/usb/usbaudio.h b/sound/usb/usbaudio.h
index 1e79986b5777..3e2b03577936 100644
--- a/sound/usb/usbaudio.h
+++ b/sound/usb/usbaudio.h
@@ -80,6 +80,7 @@ enum quirk_type {
         QUIRK_MIDI_CME,
         QUIRK_MIDI_AKAI,
         QUIRK_MIDI_US122L,
+        QUIRK_MIDI_FTDI,
         QUIRK_AUDIO_STANDARD_INTERFACE,
         QUIRK_AUDIO_FIXED_ENDPOINT,
         QUIRK_AUDIO_EDIROL_UAXX,