openwrtv3/target/linux/brcm2708/patches-4.4/0131-bcm2835-always-use-2-4-8-channels-for-multichannel-l.patch

From db9dc8093738d064963257f19b8b6d927d137dd9 Mon Sep 17 00:00:00 2001
From: wm4 <wm4@nowhere>
Date: Wed, 13 Jan 2016 19:44:03 +0100
Subject: [PATCH] bcm2835: always use 2/4/8 channels for multichannel layouts

Pad the unused channels with NA. This means userspace needs to write
additional, silent padding channels, which is not ideal, but better
than noise.

Works around noise at the following channel counts: 3, 5, 6, 7
---
 sound/arm/bcm2835-ctl.c | 89 +++++++++++++++++++++++++------------------------
 1 file changed, 45 insertions(+), 44 deletions(-)

--- a/sound/arm/bcm2835-ctl.c
+++ b/sound/arm/bcm2835-ctl.c
@@ -349,6 +349,7 @@ struct cea_channel_speaker_allocation {
 #define FRW	SNDRV_CHMAP_FRW
 #define TC	SNDRV_CHMAP_TC
 #define FCH	SNDRV_CHMAP_TFC
+#define NA	SNDRV_CHMAP_NA
 
 /*
  * CEA-861 channel maps
@@ -356,69 +357,69 @@ struct cea_channel_speaker_allocation {
  * Stolen from sound/pci/hda/patch_hdmi.c
  * (unlike the source, this uses SNDRV_* constants directly, as by the
  *  map_tables array in patch_hdmi.c)
- * Unknown entries use 0, which unfortunately is SNDRV_CHMAP_UNKNOWN instead
- * of SNDRV_CHMAP_NA.
+ * Entries which do not have a physical output channel use 0. Entries which
+ * require userspace to output silence use NA (SNDRV_CHMAP_NA).
  */
 static struct cea_channel_speaker_allocation channel_allocations[] = {
 /*			  channel:   7     6    5    4    3     2    1    0  */
 { .ca_index = 0x00,  .speakers = {   0,    0,   0,   0,   0,    0,  FR,  FL } },
 				 /* 2.1 */
-{ .ca_index = 0x01,  .speakers = {   0,    0,   0,   0,   0,  LFE,  FR,  FL } },
+{ .ca_index = 0x01,  .speakers = {   0,    0,   0,   0,  NA,  LFE,  FR,  FL } },
 				 /* Dolby Surround */
-{ .ca_index = 0x02,  .speakers = {   0,    0,   0,   0,  FC,    0,  FR,  FL } },
+{ .ca_index = 0x02,  .speakers = {   0,    0,   0,   0,  FC,   NA,  FR,  FL } },
 				 /* surround40 */
-{ .ca_index = 0x08,  .speakers = {   0,    0,  RR,  RL,   0,    0,  FR,  FL } },
+{ .ca_index = 0x08,  .speakers = {  NA,   NA,  RR,  RL,  NA,   NA,  FR,  FL } },
 				 /* surround41 */
-{ .ca_index = 0x09,  .speakers = {   0,    0,  RR,  RL,   0,  LFE,  FR,  FL } },
+{ .ca_index = 0x09,  .speakers = {  NA,   NA,  RR,  RL,  NA,  LFE,  FR,  FL } },
 				 /* surround50 */
-{ .ca_index = 0x0a,  .speakers = {   0,    0,  RR,  RL,  FC,    0,  FR,  FL } },
+{ .ca_index = 0x0a,  .speakers = {  NA,   NA,  RR,  RL,  FC,   NA,  FR,  FL } },
 				 /* surround51 */
-{ .ca_index = 0x0b,  .speakers = {   0,    0,  RR,  RL,  FC,  LFE,  FR,  FL } },
+{ .ca_index = 0x0b,  .speakers = {  NA,   NA,  RR,  RL,  FC,  LFE,  FR,  FL } },
 				 /* 6.1 */
-{ .ca_index = 0x0f,  .speakers = {   0,   RC,  RR,  RL,  FC,  LFE,  FR,  FL } },
+{ .ca_index = 0x0f,  .speakers = {  NA,   RC,  RR,  RL,  FC,  LFE,  FR,  FL } },
 				 /* surround71 */
 { .ca_index = 0x13,  .speakers = { RRC,  RLC,  RR,  RL,  FC,  LFE,  FR,  FL } },
 
-{ .ca_index = 0x03,  .speakers = {   0,    0,   0,   0,  FC,  LFE,  FR,  FL } },
-{ .ca_index = 0x04,  .speakers = {   0,    0,   0,  RC,   0,    0,  FR,  FL } },
-{ .ca_index = 0x05,  .speakers = {   0,    0,   0,  RC,   0,  LFE,  FR,  FL } },
-{ .ca_index = 0x06,  .speakers = {   0,    0,   0,  RC,  FC,    0,  FR,  FL } },
-{ .ca_index = 0x07,  .speakers = {   0,    0,   0,  RC,  FC,  LFE,  FR,  FL } },
-{ .ca_index = 0x0c,  .speakers = {   0,   RC,  RR,  RL,   0,    0,  FR,  FL } },
-{ .ca_index = 0x0d,  .speakers = {   0,   RC,  RR,  RL,   0,  LFE,  FR,  FL } },
-{ .ca_index = 0x0e,  .speakers = {   0,   RC,  RR,  RL,  FC,    0,  FR,  FL } },
-{ .ca_index = 0x10,  .speakers = { RRC,  RLC,  RR,  RL,   0,    0,  FR,  FL } },
-{ .ca_index = 0x11,  .speakers = { RRC,  RLC,  RR,  RL,   0,  LFE,  FR,  FL } },
-{ .ca_index = 0x12,  .speakers = { RRC,  RLC,  RR,  RL,  FC,    0,  FR,  FL } },
-{ .ca_index = 0x14,  .speakers = { FRC,  FLC,   0,   0,   0,    0,  FR,  FL } },
-{ .ca_index = 0x15,  .speakers = { FRC,  FLC,   0,   0,   0,  LFE,  FR,  FL } },
-{ .ca_index = 0x16,  .speakers = { FRC,  FLC,   0,   0,  FC,    0,  FR,  FL } },
-{ .ca_index = 0x17,  .speakers = { FRC,  FLC,   0,   0,  FC,  LFE,  FR,  FL } },
-{ .ca_index = 0x18,  .speakers = { FRC,  FLC,   0,  RC,   0,    0,  FR,  FL } },
-{ .ca_index = 0x19,  .speakers = { FRC,  FLC,   0,  RC,   0,  LFE,  FR,  FL } },
-{ .ca_index = 0x1a,  .speakers = { FRC,  FLC,   0,  RC,  FC,    0,  FR,  FL } },
-{ .ca_index = 0x1b,  .speakers = { FRC,  FLC,   0,  RC,  FC,  LFE,  FR,  FL } },
-{ .ca_index = 0x1c,  .speakers = { FRC,  FLC,  RR,  RL,   0,    0,  FR,  FL } },
-{ .ca_index = 0x1d,  .speakers = { FRC,  FLC,  RR,  RL,   0,  LFE,  FR,  FL } },
-{ .ca_index = 0x1e,  .speakers = { FRC,  FLC,  RR,  RL,  FC,    0,  FR,  FL } },
+{ .ca_index = 0x03,  .speakers = {  NA,   NA,  NA,  NA,  FC,  LFE,  FR,  FL } },
+{ .ca_index = 0x04,  .speakers = {  NA,   NA,  NA,  RC,  NA,   NA,  FR,  FL } },
+{ .ca_index = 0x05,  .speakers = {  NA,   NA,  NA,  RC,  NA,  LFE,  FR,  FL } },
+{ .ca_index = 0x06,  .speakers = {  NA,   NA,  NA,  RC,  FC,   NA,  FR,  FL } },
+{ .ca_index = 0x07,  .speakers = {  NA,   NA,  NA,  RC,  FC,  LFE,  FR,  FL } },
+{ .ca_index = 0x0c,  .speakers = {  NA,   RC,  RR,  RL,  NA,   NA,  FR,  FL } },
+{ .ca_index = 0x0d,  .speakers = {  NA,   RC,  RR,  RL,  NA,  LFE,  FR,  FL } },
+{ .ca_index = 0x0e,  .speakers = {  NA,   RC,  RR,  RL,  FC,   NA,  FR,  FL } },
+{ .ca_index = 0x10,  .speakers = { RRC,  RLC,  RR,  RL,  NA,   NA,  FR,  FL } },
+{ .ca_index = 0x11,  .speakers = { RRC,  RLC,  RR,  RL,  NA,  LFE,  FR,  FL } },
+{ .ca_index = 0x12,  .speakers = { RRC,  RLC,  RR,  RL,  FC,   NA,  FR,  FL } },
+{ .ca_index = 0x14,  .speakers = { FRC,  FLC,  NA,  NA,  NA,   NA,  FR,  FL } },
+{ .ca_index = 0x15,  .speakers = { FRC,  FLC,  NA,  NA,  NA,  LFE,  FR,  FL } },
+{ .ca_index = 0x16,  .speakers = { FRC,  FLC,  NA,  NA,  FC,   NA,  FR,  FL } },
+{ .ca_index = 0x17,  .speakers = { FRC,  FLC,  NA,  NA,  FC,  LFE,  FR,  FL } },
+{ .ca_index = 0x18,  .speakers = { FRC,  FLC,  NA,  RC,  NA,   NA,  FR,  FL } },
+{ .ca_index = 0x19,  .speakers = { FRC,  FLC,  NA,  RC,  NA,  LFE,  FR,  FL } },
+{ .ca_index = 0x1a,  .speakers = { FRC,  FLC,  NA,  RC,  FC,   NA,  FR,  FL } },
+{ .ca_index = 0x1b,  .speakers = { FRC,  FLC,  NA,  RC,  FC,  LFE,  FR,  FL } },
+{ .ca_index = 0x1c,  .speakers = { FRC,  FLC,  RR,  RL,  NA,   NA,  FR,  FL } },
+{ .ca_index = 0x1d,  .speakers = { FRC,  FLC,  RR,  RL,  NA,  LFE,  FR,  FL } },
+{ .ca_index = 0x1e,  .speakers = { FRC,  FLC,  RR,  RL,  FC,   NA,  FR,  FL } },
 { .ca_index = 0x1f,  .speakers = { FRC,  FLC,  RR,  RL,  FC,  LFE,  FR,  FL } },
-{ .ca_index = 0x20,  .speakers = {   0,  FCH,  RR,  RL,  FC,    0,  FR,  FL } },
-{ .ca_index = 0x21,  .speakers = {   0,  FCH,  RR,  RL,  FC,  LFE,  FR,  FL } },
-{ .ca_index = 0x22,  .speakers = {  TC,    0,  RR,  RL,  FC,    0,  FR,  FL } },
-{ .ca_index = 0x23,  .speakers = {  TC,    0,  RR,  RL,  FC,  LFE,  FR,  FL } },
-{ .ca_index = 0x24,  .speakers = { FRH,  FLH,  RR,  RL,   0,    0,  FR,  FL } },
-{ .ca_index = 0x25,  .speakers = { FRH,  FLH,  RR,  RL,   0,  LFE,  FR,  FL } },
-{ .ca_index = 0x26,  .speakers = { FRW,  FLW,  RR,  RL,   0,    0,  FR,  FL } },
-{ .ca_index = 0x27,  .speakers = { FRW,  FLW,  RR,  RL,   0,  LFE,  FR,  FL } },
-{ .ca_index = 0x28,  .speakers = {  TC,   RC,  RR,  RL,  FC,    0,  FR,  FL } },
+{ .ca_index = 0x20,  .speakers = {  NA,  FCH,  RR,  RL,  FC,   NA,  FR,  FL } },
+{ .ca_index = 0x21,  .speakers = {  NA,  FCH,  RR,  RL,  FC,  LFE,  FR,  FL } },
+{ .ca_index = 0x22,  .speakers = {  TC,   NA,  RR,  RL,  FC,   NA,  FR,  FL } },
+{ .ca_index = 0x23,  .speakers = {  TC,   NA,  RR,  RL,  FC,  LFE,  FR,  FL } },
+{ .ca_index = 0x24,  .speakers = { FRH,  FLH,  RR,  RL,  NA,   NA,  FR,  FL } },
+{ .ca_index = 0x25,  .speakers = { FRH,  FLH,  RR,  RL,  NA,  LFE,  FR,  FL } },
+{ .ca_index = 0x26,  .speakers = { FRW,  FLW,  RR,  RL,  NA,   NA,  FR,  FL } },
+{ .ca_index = 0x27,  .speakers = { FRW,  FLW,  RR,  RL,  NA,  LFE,  FR,  FL } },
+{ .ca_index = 0x28,  .speakers = {  TC,   RC,  RR,  RL,  FC,   NA,  FR,  FL } },
 { .ca_index = 0x29,  .speakers = {  TC,   RC,  RR,  RL,  FC,  LFE,  FR,  FL } },
-{ .ca_index = 0x2a,  .speakers = { FCH,   RC,  RR,  RL,  FC,    0,  FR,  FL } },
+{ .ca_index = 0x2a,  .speakers = { FCH,   RC,  RR,  RL,  FC,   NA,  FR,  FL } },
 { .ca_index = 0x2b,  .speakers = { FCH,   RC,  RR,  RL,  FC,  LFE,  FR,  FL } },
-{ .ca_index = 0x2c,  .speakers = {  TC,  FCH,  RR,  RL,  FC,    0,  FR,  FL } },
+{ .ca_index = 0x2c,  .speakers = {  TC,  FCH,  RR,  RL,  FC,   NA,  FR,  FL } },
 { .ca_index = 0x2d,  .speakers = {  TC,  FCH,  RR,  RL,  FC,  LFE,  FR,  FL } },
-{ .ca_index = 0x2e,  .speakers = { FRH,  FLH,  RR,  RL,  FC,    0,  FR,  FL } },
+{ .ca_index = 0x2e,  .speakers = { FRH,  FLH,  RR,  RL,  FC,   NA,  FR,  FL } },
 { .ca_index = 0x2f,  .speakers = { FRH,  FLH,  RR,  RL,  FC,  LFE,  FR,  FL } },
-{ .ca_index = 0x30,  .speakers = { FRW,  FLW,  RR,  RL,  FC,    0,  FR,  FL } },
+{ .ca_index = 0x30,  .speakers = { FRW,  FLW,  RR,  RL,  FC,   NA,  FR,  FL } },
 { .ca_index = 0x31,  .speakers = { FRW,  FLW,  RR,  RL,  FC,  LFE,  FR,  FL } },
 };