ALSA: pcm: add IEC958 channel status helper

Add a helper to create the IEC958 channel status from an ALSA
snd_pcm_runtime structure, taking account of the sample rate and
sample size.

Signed-off-by: Russell King <[e-mail]>
Reviwed-by: Mark Brown <[e-mail]>
Signed-off-by: Takashi Iwai <[e-mail]>

include/sound/pcm_iec958.h

···
+#ifndef __SOUND_PCM_IEC958_H
+#define __SOUND_PCM_IEC958_H
+
+#include <linux/types.h>
+
+int snd_pcm_create_iec958_consumer(struct snd_pcm_runtime *runtime, u8 *cs,
+	size_t len);
+
+#endif

sound/core/Kconfig

···
 config SND_PCM_ELD
 	bool
 
+config SND_PCM_IEC958
+	bool
+
 config SND_DMAENGINE_PCM
 	tristate
 

sound/core/Makefile

···
 		pcm_memory.o memalloc.o
 snd-pcm-$(CONFIG_SND_DMA_SGBUF) += sgbuf.o
 snd-pcm-$(CONFIG_SND_PCM_ELD) += pcm_drm_eld.o
+snd-pcm-$(CONFIG_SND_PCM_IEC958) += pcm_iec958.o
 
 # for trace-points
 CFLAGS_pcm_lib.o := -I$(src)

sound/core/pcm_iec958.c

···
+/*
+ *  PCM DRM helpers
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License version 2 as
+ *   published by the Free Software Foundation.
+ */
+#include <linux/export.h>
+#include <linux/types.h>
+#include <sound/asoundef.h>
+#include <sound/pcm.h>
+#include <sound/pcm_iec958.h>
+
+/**
+ * snd_pcm_create_iec958_consumer - create consumer format IEC958 channel status
+ * @runtime: pcm runtime structure with ->rate filled in
+ * @cs: channel status buffer, at least four bytes
+ * @len: length of channel status buffer
+ *
+ * Create the consumer format channel status data in @cs of maximum size
+ * @len corresponding to the parameters of the PCM runtime @runtime.
+ *
+ * Drivers may wish to tweak the contents of the buffer after creation.
+ *
+ * Returns: length of buffer, or negative error code if something failed.
+ */
+int snd_pcm_create_iec958_consumer(struct snd_pcm_runtime *runtime, u8 *cs,
+	size_t len)
+{
+	unsigned int fs, ws;
+
+	if (len < 4)
+		return -EINVAL;
+
+	switch (runtime->rate) {
+	case 32000:
+		fs = IEC958_AES3_CON_FS_32000;
+		break;
+	case 44100:
+		fs = IEC958_AES3_CON_FS_44100;
+		break;
+	case 48000:
+		fs = IEC958_AES3_CON_FS_48000;
+		break;
+	case 88200:
+		fs = IEC958_AES3_CON_FS_88200;
+		break;
+	case 96000:
+		fs = IEC958_AES3_CON_FS_96000;
+		break;
+	case 176400:
+		fs = IEC958_AES3_CON_FS_176400;
+		break;
+	case 192000:
+		fs = IEC958_AES3_CON_FS_192000;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (len > 4) {
+		switch (snd_pcm_format_width(runtime->format)) {
+		case 16:
+			ws = IEC958_AES4_CON_WORDLEN_20_16;
+			break;
+		case 18:
+			ws = IEC958_AES4_CON_WORDLEN_22_18;
+			break;
+		case 20:
+			ws = IEC958_AES4_CON_WORDLEN_20_16 |
+			     IEC958_AES4_CON_MAX_WORDLEN_24;
+			break;
+		case 24:
+			ws = IEC958_AES4_CON_WORDLEN_24_20 |
+			     IEC958_AES4_CON_MAX_WORDLEN_24;
+			break;
+
+		default:
+			return -EINVAL;
+		}
+	}
+
+	memset(cs, 0, len);
+
+	cs[0] = IEC958_AES0_CON_NOT_COPYRIGHT | IEC958_AES0_CON_EMPHASIS_NONE;
+	cs[1] = IEC958_AES1_CON_GENERAL;
+	cs[2] = IEC958_AES2_CON_SOURCE_UNSPEC | IEC958_AES2_CON_CHANNEL_UNSPEC;
+	cs[3] = IEC958_AES3_CON_CLOCK_1000PPM | fs;
+
+	if (len > 4)
+		cs[4] = ws;
+
+	return len;
+}
+EXPORT_SYMBOL(snd_pcm_create_iec958_consumer);