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diff --git a/sound/oss/emu10k1/passthrough.h b/sound/oss/emu10k1/passthrough.h
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+++ b/sound/oss/emu10k1/passthrough.h
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+/*
+ **********************************************************************
+ *     passthrough.h -- Emu10k1 digital passthrough header file
+ *     Copyright (C) 2001  Juha Yrjölä <jyrjola@cc.hut.fi>
+ *
+ **********************************************************************
+ *
+ *     Date                 Author          Summary of changes
+ *     ----                 ------          ------------------
+ *     May 15, 2001         Juha Yrjölä     base code release
+ *
+ **********************************************************************
+ *
+ *     This program is free software; you can redistribute it and/or
+ *     modify it under the terms of the GNU General Public License as
+ *     published by the Free Software Foundation; either version 2 of
+ *     the License, or (at your option) any later version.
+ *
+ *     This program is distributed in the hope that it will be useful,
+ *     but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *     GNU General Public License for more details.
+ *
+ *     You should have received a copy of the GNU General Public
+ *     License along with this program; if not, write to the Free
+ *     Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139,
+ *     USA.
+ *
+ **********************************************************************
+ */
+
+#ifndef _PASSTHROUGH_H
+#define _PASSTHROUGH_H
+
+#include "audio.h"
+
+/* number of 16-bit stereo samples in XTRAM buffer */
+#define PT_SAMPLES 0x8000
+#define PT_BLOCKSAMPLES 0x400
+#define PT_BLOCKSIZE (PT_BLOCKSAMPLES*4)
+#define PT_BLOCKSIZE_LOG2 12
+#define PT_BLOCKCOUNT (PT_SAMPLES/PT_BLOCKSAMPLES)
+#define PT_INITPTR (PT_SAMPLES/2-1)
+
+#define PT_STATE_INACTIVE 0
+#define PT_STATE_ACTIVATED 1
+#define PT_STATE_PLAYING 2
+
+/* passthrough struct */
+struct pt_data
+{
+        u8      selected, state, spcs_to_use;
+        int     intr_gpr, enable_gpr, pos_gpr;
+        u32     blocks_played, blocks_copied, old_spcs[3];
+        u32     playptr, copyptr;
+        u32     prepend_size;
+        u8      *buf;
+        u8      ac3data;
+
+        char    *patch_name, *intr_gpr_name, *enable_gpr_name, *pos_gpr_name;
+
+        wait_queue_head_t wait;
+        spinlock_t lock;
+};
+
+/*
+  Passthrough can be done in two methods:
+
+  Method 1 : tram
+     In original emu10k1, we couldn't bypass the sample rate converters. Even at 48kHz
+     (the internal sample rate of the emu10k1) the samples would get messed up.
+     To over come this, samples are copied into the tram and a special dsp patch copies
+     the samples out and generates interrupts when a block has finnished playing.
+
+  Method 2 : Interpolator bypass
+
+     Creative fixed the sample rate convert problem in emu10k1 rev 7 and higher
+     (including the emu10k2 (audigy)). This allows us to use the regular, and much simpler
+     playback method. 
+
+
+  In both methods, dsp code is used to mux audio and passthrough. This ensures that the spdif
+  doesn't receive audio and pasthrough data at the same time. The spdif flag SPCS_NOTAUDIODATA
+  is set to tell 
+
+ */
+
+// emu10k1 revs greater than or equal to 7 can use method2
+
+#define USE_PT_METHOD2  (card->is_audigy)
+#define USE_PT_METHOD1  !USE_PT_METHOD2
+
+ssize_t emu10k1_pt_write(struct file *file, const char __user *buf, size_t count);
+
+int emu10k1_pt_setup(struct emu10k1_wavedevice *wave_dev);
+void emu10k1_pt_stop(struct emu10k1_card *card);
+void emu10k1_pt_waveout_update(struct emu10k1_wavedevice *wave_dev);
+
+#endif /* _PASSTHROUGH_H */