From 3a572d94bcff98a14c94fe686881a169a26f3fca Mon Sep 17 00:00:00 2001
From: Jussi Laako <jussi@sonarnerd.net>
Date: Wed, 13 Jun 2018 01:43:01 +0300
Subject: [PATCH] ALSA: usb-audio: Add native DSD support for Mytek DACs
Git-commit: 3a572d94bcff98a14c94fe686881a169a26f3fca
Patch-mainline: v4.18-rc1
References: bsc#1051510

Add new mostly generic code with Mytek VID to support native DSD mode.

This implementation should be easier to maintain when manufacturers
release new products.

Signed-off-by: Jussi Laako <jussi@sonarnerd.net>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

---
 sound/usb/card.h   |    1 +
 sound/usb/format.c |    5 ++++-
 sound/usb/quirks.c |   13 +++++++++++++
 3 files changed, 18 insertions(+), 1 deletion(-)

--- a/sound/usb/card.h
+++ b/sound/usb/card.h
@@ -31,6 +31,7 @@ struct audioformat {
 	struct snd_pcm_chmap_elem *chmap; /* (optional) channel map */
 	bool dsd_dop;			/* add DOP headers in case of DSD samples */
 	bool dsd_bitrev;		/* reverse the bits of each DSD sample */
+	bool dsd_raw;			/* altsetting is raw DSD */
 };
 
 struct snd_usb_substream;
--- a/sound/usb/format.c
+++ b/sound/usb/format.c
@@ -63,8 +63,11 @@ static u64 parse_audio_format_i_type(str
 		sample_width = fmt->bBitResolution;
 		sample_bytes = fmt->bSubslotSize;
 
-		if (format & UAC2_FORMAT_TYPE_I_RAW_DATA)
+		if (format & UAC2_FORMAT_TYPE_I_RAW_DATA) {
 			pcm_formats |= SNDRV_PCM_FMTBIT_SPECIAL;
+			/* flag potentially raw DSD capable altsettings */
+			fp->dsd_raw = true;
+		}
 
 		format <<= 1;
 		break;
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -1444,6 +1444,19 @@ u64 snd_usb_interface_dsd_format_quirks(
 			return SNDRV_PCM_FMTBIT_DSD_U32_BE;
 	}
 
+	/* Mostly generic method to detect many DSD-capable implementations -
+	 * from XMOS/Thesycon
+	 */
+	switch (USB_ID_VENDOR(chip->usb_id)) {
+	case 0x25ce:  /* Mytek devices */
+		if (fp->dsd_raw)
+			return SNDRV_PCM_FMTBIT_DSD_U32_BE;
+		break;
+	default:
+		break;
+
+	}
+
 	return 0;
 }