target/linux/brcm2708/patches-4.4/0250-bcm2835-add-fallback-channel-layouts-if-channel-map-.patch

   1 From 7c2791eb1e01c8714d5553bd2bd5e611394a6517 Mon Sep 17 00:00:00 2001
   2 From: wm4 <wm4@nowhere>
   3 Date: Tue, 19 Apr 2016 16:29:41 +0200
   4 Subject: [PATCH 250/423] bcm2835: add fallback channel layouts if channel map
   5  API is not used
   6
   7 Should be more useful than just forcing stereo.
   8
   9 We can't match the exact legacy ALSA channel layouts, so this is a
  10 "best effort" hack.
  11
  12 I'm not sure what happens if the application requests channel counts
  13 that are not power-of-2s. The channel map API hopefully forces
  14 applications which use the channel map API to request the correct
  15 count by adding padding channels, but the bare API enforces
  16 nothing. Possibly this could be added to rate_hw_constraint_channels
  17 at a later point.
  18 ---
  19  sound/arm/bcm2835-vchiq.c | 11 ++++++++++-
  20  1 file changed, 10 insertions(+), 1 deletion(-)
  21
  22 --- a/sound/arm/bcm2835-vchiq.c
  23 +++ b/sound/arm/bcm2835-vchiq.c
  24 @@ -598,7 +598,16 @@ int bcm2835_audio_set_params(bcm2835_als
  25         if (alsa_stream->chip->cea_chmap >= 0) {
  26                 chmap_value = (unsigned)alsa_stream->chip->cea_chmap << 24;
  27         } else {
  28 -               chmap_value = 0; /* force stereo */
  29 +               /* fallback layouts for applications which do not use chmap API */
  30 +               chmap_value = 0x00;
  31 +               switch (channels) {
  32 +               case 3: chmap_value = 0x01; break;
  33 +               case 4: chmap_value = 0x03; break;
  34 +               case 5: chmap_value = 0x07; break;
  35 +               case 6: chmap_value = 0x0b; break;
  36 +               case 7: chmap_value = 0x0f; break;
  37 +               case 8: chmap_value = 0x13; break;
  38 +               }
  39                 for (i = 0; i < 8; i++)
  40                         alsa_stream->chip->map_channels[i] = i;
  41         }