[Sound-open-firmware] about multiple BE dai_links support

[Keyon Jie]

Hi all,

As we are using link->id for BE dai_link match in 
snd_soc_find_dai_link(), so the link->id define in machine driver is 
crucial.

Previously we set all link->id to be 0s in machine drivers(e.g. 
nocodec.c, bytcr_rt5651.c, cnl_rt274.c, bxt_pcm512x.c...), but in many 
other cAVS machine drivers(skl_rt286.c, kbl_rt5663_max98927.c, 
bxt_tdf8532.c, ...), they are using different link->id for different BE 
dai_links.

So, to reuse those machine driver and BE dai_links for SOF, we have 2 
solution to fix this:

1. remove the hardcode(to 0) of link->id in topology and add a param for 
that. I provide a RFC patch below.

2. change snd_soc_find_dai_link(), remove the link->id comparison.

Personally I don't like the #2 solution, it will lead to backward 
compatibility issue for those exist drivers, and also is mismatch with 
the comment of snd_soc_find_dai_link():
  * @id: DAI link ID to match
  * @name: DAI link name to match, optional
  * @stream_name: DAI link stream name to match, optional

Hi Pierre/Liam, any comments on this? I hope we can align this soon then 
I can refine and send machine driver for GPMRB.


Thanks,
~Keyon

diff --git a/topology/m4/dai.m4 b/topology/m4/dai.m4
index 0b030af..0a79364 100644
--- a/topology/m4/dai.m4
+++ b/topology/m4/dai.m4
@@ -140,17 +140,17 @@ define(`DAI_TDM',
  dnl DAI Config)
  define(`N_DAI_CONFIG', `DAICONFIG.'$1)

-dnl DAI_CONFIG(type, idx, name, format, valid bits, mclk, bclk, fsync, tdm)
+dnl DAI_CONFIG(type, idx, link_id, name, format, valid bits, mclk, 
bclk, fsync, tdm)
  define(`DAI_CONFIG',
  `SectionHWConfig."'$1$2`" {'
  `'
  `      id              "'$2`"'
  `      format          "'$4`"'
  `'
-`      '$6
  `      '$7
  `      '$8
  `      '$9
+`      '$10
  `}'
  `SectionVendorTuples."'N_DAI_CONFIG($1$2)`_tuples_str" {'
  `      tokens "sof_dai_tokens"'
@@ -164,15 +164,15 @@ define(`DAI_CONFIG',
  `SectionVendorTuples."'N_DAI_CONFIG($1$2)`_tuples" {'
  `      tokens "sof_dai_tokens"'
  `      tuples."word" {'
-`              SOF_TKN_DAI_SAMPLE_BITS'        STR($5)
+`              SOF_TKN_DAI_SAMPLE_BITS'        STR($6)
  `      }'
  `}'
  `SectionData."'N_DAI_CONFIG($1$2)`_data" {'
  `      tuples "'N_DAI_CONFIG($1$2)`_tuples"'
  `}'
  `'
-`SectionBE."'$3`" {'
-`      index "0"'
+`SectionBE."'$4`" {'
+`      index "'$3`"'
  `      default_hw_conf_id      "'$2`"'
  `'
  `      hw_configs ['