[PATCH 1/2] sound: line6: correct midi status byte when receiving data from podxt

[Artem Egorkine <arteme@gmail.com>]

A PODxt device sends 0xb2, 0xc2 or 0xf2 as a status byte for MIDI
messages over USB that should otherwise have a 0xb0, 0xc0 or 0xf0
status byte. This is usually corrected by the driver on other OSes.

This fixes MIDI sysex messages sent by PODxt.

Signed-off-by: Artem Egorkine <arteme@gmail.com>
---
 sound/usb/line6/driver.c  |  2 +-
 sound/usb/line6/midi.c    |  2 +-
 sound/usb/line6/midibuf.c | 42 +++++++++++++++++++++++++++++++--------
 sound/usb/line6/midibuf.h |  2 +-
 sound/usb/line6/pod.c     |  3 ++-
 5 files changed, 39 insertions(+), 12 deletions(-)

diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c
index 59faa5a9a714..4dbe7bce3ee8 100644
--- a/sound/usb/line6/driver.c
+++ b/sound/usb/line6/driver.c
@@ -304,7 +304,7 @@ static void line6_data_received(struct urb *urb)
 		for (;;) {
 			done =
 				line6_midibuf_read(mb, line6->buffer_message,
-						LINE6_MIDI_MESSAGE_MAXLEN);
+						LINE6_MIDI_MESSAGE_MAXLEN, 1);
 
 			if (done <= 0)
 				break;
diff --git a/sound/usb/line6/midi.c b/sound/usb/line6/midi.c
index ba0e2b7e8fe1..335f8d531548 100644
--- a/sound/usb/line6/midi.c
+++ b/sound/usb/line6/midi.c
@@ -56,7 +56,7 @@ static void line6_midi_transmit(struct snd_rawmidi_substream *substream)
 
 	for (;;) {
 		done = line6_midibuf_read(mb, chunk,
-					  LINE6_FALLBACK_MAXPACKETSIZE);
+					  LINE6_FALLBACK_MAXPACKETSIZE, 0);
 
 		if (done == 0)
 			break;
diff --git a/sound/usb/line6/midibuf.c b/sound/usb/line6/midibuf.c
index 6a70463f82c4..ba7a2243cf68 100644
--- a/sound/usb/line6/midibuf.c
+++ b/sound/usb/line6/midibuf.c
@@ -9,6 +9,22 @@
 
 #include "midibuf.h"
 
+/* #define DUMP_BUFFERS */
+
+#ifdef DUMP_BUFFERS
+static void dump_buffer(char rx, const u8 *data, int length)
+{
+	const char* type = rx ? "rx" : "tx";
+        printk(KERN_DEBUG "%s packet: [", type);
+        for (; length > 0; ++data, --length)
+                printk(KERN_CONT " %02x", *data);
+        printk(KERN_CONT " ]\n");
+}
+#else
+#define dump_buffer(rx, data, length) /* nothing */
+#endif
+
+
 static int midibuf_message_length(unsigned char code)
 {
 	int message_length;
@@ -20,12 +36,7 @@ static int midibuf_message_length(unsigned char code)
 
 		message_length = length[(code >> 4) - 8];
 	} else {
-		/*
-		   Note that according to the MIDI specification 0xf2 is
-		   the "Song Position Pointer", but this is used by Line 6
-		   to send sysex messages to the host.
-		 */
-		static const int length[] = { -1, 2, -1, 2, -1, -1, 1, 1, 1, 1,
+		static const int length[] = { -1, 2, 2, 2, -1, -1, 1, 1, 1, -1,
 			1, 1, 1, -1, 1, 1
 		};
 		message_length = length[code & 0x0f];
@@ -125,7 +136,7 @@ int line6_midibuf_write(struct midi_buffer *this, unsigned char *data,
 }
 
 int line6_midibuf_read(struct midi_buffer *this, unsigned char *data,
-		       int length)
+		       int length, char rx)
 {
 	int bytes_used;
 	int length1, length2;
@@ -148,9 +159,22 @@ int line6_midibuf_read(struct midi_buffer *this, unsigned char *data,
 
 	length1 = this->size - this->pos_read;
 
-	/* check MIDI command length */
 	command = this->buf[this->pos_read];
+	/*
+	   PODxt always has status byte lower nibble set to 0010,
+	   when it means to send 0000, so we correct if here so
+	   that control/program changes come on channel 1 and
+	   sysex message status byte is correct
+	 */
+	if (rx) {
+		if (command == 0xb2 || command == 0xc2 || command == 0xf2) {
+			unsigned char fixed = command & 0xf0;
+			this->buf[this->pos_read] = fixed;
+			command = fixed;
+		}
+	}
 
+	/* check MIDI command length */
 	if (command & 0x80) {
 		midi_length = midibuf_message_length(command);
 		this->command_prev = command;
@@ -222,6 +246,8 @@ int line6_midibuf_read(struct midi_buffer *this, unsigned char *data,
 		this->pos_read = length2;
 	}
 
+	dump_buffer(rx, data, length + repeat);
+
 	if (repeat)
 		data[0] = this->command_prev;
 
diff --git a/sound/usb/line6/midibuf.h b/sound/usb/line6/midibuf.h
index 124a8f9f7e96..8342e45046b0 100644
--- a/sound/usb/line6/midibuf.h
+++ b/sound/usb/line6/midibuf.h
@@ -23,7 +23,7 @@ extern void line6_midibuf_destroy(struct midi_buffer *mb);
 extern int line6_midibuf_ignore(struct midi_buffer *mb, int length);
 extern int line6_midibuf_init(struct midi_buffer *mb, int size, int split);
 extern int line6_midibuf_read(struct midi_buffer *mb, unsigned char *data,
-			      int length);
+			      int length, char rx);
 extern void line6_midibuf_reset(struct midi_buffer *mb);
 extern int line6_midibuf_write(struct midi_buffer *mb, unsigned char *data,
 			       int length);
diff --git a/sound/usb/line6/pod.c b/sound/usb/line6/pod.c
index cd41aa7f0385..d173971e5f02 100644
--- a/sound/usb/line6/pod.c
+++ b/sound/usb/line6/pod.c
@@ -159,8 +159,9 @@ static struct line6_pcm_properties pod_pcm_properties = {
 	.bytes_per_channel = 3 /* SNDRV_PCM_FMTBIT_S24_3LE */
 };
 
+
 static const char pod_version_header[] = {
-	0xf2, 0x7e, 0x7f, 0x06, 0x02
+	0xf0, 0x7e, 0x7f, 0x06, 0x02
 };
 
 static char *pod_alloc_sysex_buffer(struct usb_line6_pod *pod, int code,
-- 
2.38.1