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List:       linux-sound
Subject:    [PATCH][2.2.x,2.4.x] OSS MIDI output loses data
From:       Clemens Ladisch <clemens () ladisch ! de>
Date:       2002-11-28 12:10:34
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In the 2.1.6 kernel, the output loop in midi_poll() was changed to enable
interrupts during the outputc() call. Unfortunately, the check whether the
device has accepted the current byte ("ok") was moved behind the code
which removes the byte from the output queue, so one byte would be lost
every time the hardware FIFO is full.

-- 
Clemens


--- linux-2.4.19/drivers/sound/midibuf.c	Wed Nov 27 12:34:56 2002
+++ linux/drivers/sound/midibuf.c	Wed Nov 27 16:32:31 2002
@@ -129,15 +129,16 @@
 		for (dev = 0; dev < num_midis; dev++)
 			if (midi_devs[dev] != NULL && midi_out_buf[dev] != NULL)
 			{
-				int ok = 1;
-
-				while (DATA_AVAIL(midi_out_buf[dev]) && ok)
+				while (DATA_AVAIL(midi_out_buf[dev]))
 				{
+					int ok;
 					int c = midi_out_buf[dev]->queue[midi_out_buf[dev]->head];

 					restore_flags(flags);	/* Give some time to others */
 					ok = midi_devs[dev]->outputc(dev, c);
 					cli();
+					if (!ok)
+						break;
 					midi_out_buf[dev]->head = (midi_out_buf[dev]->head + 1) % MAX_QUEUE_SIZE;
 					midi_out_buf[dev]->len--;
 				}

-
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