From 6dbaf8b913f2976ee776beb7c8bb0c52c7066ced Mon Sep 17 00:00:00 2001
From: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Date: Tue, 23 May 2017 22:40:42 +0900
Subject: [PATCH] ALSA: sb: remove needless evaluation in implementation for copy callback
Git-commit: 6dbaf8b913f2976ee776beb7c8bb0c52c7066ced
Patch-mainline: v4.13-rc1
References: bsc#1121278

In design of ALSA pcm core, 'struct snd_pcm_ops.copy' is expected to
copy PCM frames, according to frame alignment on intermediate buffer for
userspace and dedicated buffer for data transmission. In this callback,
value of 'channel' argument depends on the frame alignment, which drivers
registers to runtime of PCM substream. When target devices can handle
non-interleaved buffer, this value has positive value, otherwise negative.

ALSA driver for PCM component of EMU8000 chip is programmed with local
macro to switch the frame alignment. The 'copy' operation in
non-interleaved side has evaluation of the 'channel' argument (actually
it's 'voice' argument). This is useless.

This commit remove the evaluation.

[tiwai: the negative channel argument was the inheritance from the old code where -1 was meant for interleaved mode.  The mix-up was dropped meanwhile, thus it's correct to assume that we receive no longer -1 there, and it's safe to cleanup the relevant code.

 Also, voice=0 for channel==1 is trivial, and it can be dropped, too.]

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

---
 sound/isa/sb/emu8000_pcm.c | 28 +++-------------------------
 1 file changed, 3 insertions(+), 25 deletions(-)

diff --git a/sound/isa/sb/emu8000_pcm.c b/sound/isa/sb/emu8000_pcm.c
index 32f234f494e5..c480024422af 100644
--- a/sound/isa/sb/emu8000_pcm.c
+++ b/sound/isa/sb/emu8000_pcm.c
@@ -450,20 +450,8 @@ static int emu8k_pcm_copy(struct snd_pcm_substream *subs,
 	struct snd_emu8000 *emu = rec->emu;
 
 	snd_emu8000_write_wait(emu, 1);
-	if (voice == -1) {
-		unsigned short *buf = src;
-		int i, err;
-		count /= rec->voices;
-		for (i = 0; i < rec->voices; i++) {
-			err = emu8k_transfer_block(emu, pos + rec->loop_start[i], buf, count);
-			if (err < 0)
-				return err;
-			buf += count;
-		}
-		return 0;
-	} else {
-		return emu8k_transfer_block(emu, pos + rec->loop_start[voice], src, count);
-	}
+	return emu8k_transfer_block(emu, pos + rec->loop_start[voice], src,
+				    count);
 }
 
 /* make a channel block silence */
@@ -487,17 +475,7 @@ static int emu8k_pcm_silence(struct snd_pcm_substream *subs,
 	struct snd_emu8000 *emu = rec->emu;
 
 	snd_emu8000_write_wait(emu, 1);
-	if (voice == -1 && rec->voices == 1)
-		voice = 0;
-	if (voice == -1) {
-		int err;
-		err = emu8k_silence_block(emu, pos + rec->loop_start[0], count / 2);
-		if (err < 0)
-			return err;
-		return emu8k_silence_block(emu, pos + rec->loop_start[1], count / 2);
-	} else {
-		return emu8k_silence_block(emu, pos + rec->loop_start[voice], count);
-	}
+	return emu8k_silence_block(emu, pos + rec->loop_start[voice], count);
 }
 
 #else /* interleave */
-- 
2.20.1