patch-2.1.6 linux/drivers/sound/pas2_midi.c

• Lines: 191
• Date: Tue Oct 29 16:36:36 1996
• Orig file: v2.1.5/linux/drivers/sound/pas2_midi.c
• Orig date: Sun Jun 30 12:31:09 1996

diff -u --recursive --new-file v2.1.5/linux/drivers/sound/pas2_midi.c linux/drivers/sound/pas2_midi.c
@@ -4,15 +4,13 @@
  * The low level driver for the PAS Midi Interface.
  */
 
-#include <linux/config.h>
-
 #include "sound_config.h"
+#include <linux/config.h>
 
 #if defined(CONFIG_PAS) && defined(CONFIG_MIDI)
 
 static int      midi_busy = 0, input_opened = 0;
 static int      my_dev;
-static volatile int ofifo_bytes = 0;
 
 static unsigned char tmp_queue[256];
 static volatile int qlen;
@@ -34,7 +32,7 @@
   if (midi_busy)
     {
       printk ("PAS2: Midi busy\n");
-      return -(EBUSY);
+      return -EBUSY;
     }
 
   /*
@@ -59,29 +57,22 @@
 
   if (mode == OPEN_READ || mode == OPEN_READWRITE)
     {
-      ctrl |= 0x04;		/*
-				   * Enable input
-				 */
+      ctrl |= 0x04;		/* Enable input */
       input_opened = 1;
     }
 
   if (mode == OPEN_WRITE || mode == OPEN_READWRITE)
     {
-      ctrl |= 0x08 |		/*
-				   * Enable output
-				 */
-	0x10;
+      ctrl |= 0x08 | 0x10;	/* Enable output */
     }
 
-  pas_write (ctrl,
-	     0x178b);
+  pas_write (ctrl, 0x178b);
 
   /*
    * Acknowledge any pending interrupts
    */
 
   pas_write (0xff, 0x1B88);
-  ofifo_bytes = 0;
 
   restore_flags (flags);
 
@@ -110,18 +101,19 @@
 
   fifo_space = ((x = pas_read (0x1B89)) >> 4) & 0x0f;
 
-  if (fifo_space == 15 || (fifo_space < 2 && ofifo_bytes > 13))		/*
-									   * Fifo
-									   * full
-									 */
+/*
+ * The MIDI FIFO space register and it's documentation is nonunderstandable.
+ * There seem to be no way to differentiate between buffer full and buffer
+ * empty situations. For this reason we don't never write the buffer
+ * completely full. In this way we can assume that 0 (or is it 15)
+ * means that the buffer is empty.
+ */
+
+  if (fifo_space < 2 && fifo_space != 0)	/* Full (almost) */
     {
-      return 0;			/*
-				 * Upper layer will call again
-				 */
+      return 0;			/* Ask upper layers to retry after some time */
     }
 
-  ofifo_bytes++;
-
   pas_write (midi_byte, 0x178A);
 
   return 1;
@@ -154,18 +146,14 @@
 
   if (!qlen)
     if (dump_to_midi (midi_byte))
-      return 1;			/*
-				 * OK
-				 */
+      return 1;
 
   /*
    * Put to the local queue
    */
 
   if (qlen >= 256)
-    return 0;			/*
-				 * Local queue full
-				 */
+    return 0;			/* Local queue full */
 
   save_flags (flags);
   cli ();
@@ -194,13 +182,12 @@
 static int
 pas_midi_ioctl (int dev, unsigned cmd, caddr_t arg)
 {
-  return -(EINVAL);
+  return -EINVAL;
 }
 
 static void
 pas_midi_kick (int dev)
 {
-  ofifo_bytes = 0;
 }
 
 static int
@@ -225,9 +212,7 @@
   pas_midi_start_read,
   pas_midi_end_read,
   pas_midi_kick,
-  NULL,				/*
-				 * command
-				 */
+  NULL,
   pas_buffer_status,
   NULL
 };
@@ -254,13 +239,9 @@
 
   stat = pas_read (0x1B88);
 
-  if (stat & 0x04)		/*
-				   * Input byte available
-				 */
+  if (stat & 0x04)		/* Input data available */
     {
-      incount = pas_read (0x1B89) & 0x0f;	/*
-						   * Input FIFO count
-						 */
+      incount = pas_read (0x1B89) & 0x0f;	/* Input FIFO size */
       if (!incount)
 	incount = 16;
 
@@ -270,22 +251,11 @@
 	    midi_input_intr (my_dev, pas_read (0x178A));
 	  }
 	else
-	  pas_read (0x178A);	/*
-				 * Flush
-				 */
+	  pas_read (0x178A);	/* Flush */
     }
 
   if (stat & (0x08 | 0x10))
     {
-      if (!(stat & 0x08))
-	{
-	  ofifo_bytes = 8;
-	}
-      else
-	{
-	  ofifo_bytes = 0;
-	}
-
       save_flags (flags);
       cli ();
 
@@ -301,13 +271,10 @@
 
   if (stat & 0x40)
     {
-      printk ("MIDI output overrun %x,%x,%d \n", pas_read (0x1B89), stat, ofifo_bytes);
-      ofifo_bytes = 100;
+      printk ("MIDI output overrun %x,%x\n", pas_read (0x1B89), stat);
     }
 
-  pas_write (stat, 0x1B88);	/*
-				   * Acknowledge interrupts
-				 */
+  pas_write (stat, 0x1B88);	/* Acknowledge interrupts */
 }
 
 #endif