asound.conf , route path,

/etc/asound.conf 有 alsa 裝置的配置開關.

有關 codec routing 部份.,,,

先看 driver 的 snd_soc_dapm_route 矩陣
.先把array copy 出來。
https://gist.github.com/checko/eb5fd55bfd7baa25ddd4

每個 element 有三個欄位. (OUT, SW, IN).

看 電路，決定一下 route 的 in, out.
以 play 來說，:
out 是 HPOL, HPOR.
input 是 I2S 第一組

找 array 中，OUT 欄位是 HPOL. HPOR 的..

 { "HPOL", NULL, "HP Amp" },
 { "HPOL", NULL, "HP L Amp" },
 { "HPOL", NULL, "Improve HP Amp Drv" },

 { "HPOR", NULL, "HP Amp" },
 { "HPOR", NULL, "HP R Amp" },
 { "HPOR", NULL, "Improve HP Amp Drv" },

所以可以知道HPO 可以有三個 input path 可以選 : HP AMP. HP L/R Amp, Improved HP Amp Drv

其中 HP L/R Amp 和 Improve HP Amp Drv 都沒有 input path, 只有 HP Amp 有:

 { "HP Amp", NULL, "HPO MIX" },
 { "HP Amp", NULL, "JD Power" },
 { "HP Amp", NULL, "Mic Det Power" },

一樣，其中只有 HPO MIX有 input source:

 { "HPO MIX", "DAC1 Switch", "DAC 1" },
 { "HPO MIX", "HPVOL Switch", "HPOVOL" },

HPOVOL 的話，要經過..

 { "HPOVOL", NULL, "HPOVOL MIXL" },
 { "HPOVOL", NULL, "HPOVOL MIXR" },

只看 HPOVOL MIXL (因為沒有要 swap L/R, or mono):

 { "HPOVOL MIXL", "DAC1 Switch", "DAC L1" },
 { "HPOVOL MIXL", "INL Switch", "INL VOL" },

有兩個選項，一個 DAC L1 (跟剛剛 HPO MIX 一樣), 另一個是 INL VOL

IN VOL 接到 Analog Input，所以不是我們要用的。
看 DAC L1:

 { "DAC L1", NULL, "Stereo DAC MIXL" },
 { "DAC L1", NULL, "PLL1", check_sysclk1_source },

其中 PLL1 會 trigger check_sysclk_source, 同時也沒有 input，所以只看 Stereo DAC MIXL:

 { "Stereo DAC MIXL", "DAC L1 Switch", "DAC1 MIXL" },
 { "Stereo DAC MIXL", "DAC R1 Switch", "DAC1 MIXR" },
 { "Stereo DAC MIXL", "DAC L2 Switch", "DAC L2 Volume" },
 { "Stereo DAC MIXL", NULL, "dac stereo1 filter" },
 { "Stereo DAC MIXL", NULL, "DAC L1 Power" },

DAC L1 Power 和 dac stereo1 filter 沒有 input,
IF1_DAC (也就是 I2S 第一組)，有 0-7 共 8組 DAC...(!!)
DAC L1 接到 SounzReal, DAC L2 接到 Voice, 所以先看簡單的. DAC1 MIXL..

 { "DAC1 MIXL", "Stereo ADC Switch", "Stereo1 ADC MIXL" },
 { "DAC1 MIXL", "DAC1 Switch", "DAC1 L Mux" },
 { "DAC1 MIXL", NULL, "dac stereo1 filter" },
 { "DAC1 MIXL", NULL, "DAC L1 Power" },

dac stereo1 filter, DAC L1 Power 一樣，沒有 input.
Stereo1 ADC MIXL 接到 Analog Input ADC 哪一路，
所以應該是要看 DAC1 L Mux:

 { "DAC1 L Mux", "IF1 DAC", "IF1 DAC1 L" },
 { "DAC1 L Mux", "IF2 DAC", "IF2 DAC L" },

要 route 到 I2S 第一路，所以選 IF1 DAC1 L:

 { "IF1 DAC1 L", NULL, "IF1 DAC1" },

IF1 DAC1 的 source 有兩個：

 { "IF1 DAC1", NULL, "AIF1RX" },
 { "IF1 DAC1", NULL, "I2S1" },

好像就是最後了....
最後是..

#ifdef USE_ASRC
 {"I2S1", NULL, "ASRC enable"},
 {"I2S2", NULL, "ASRC enable"},
#endif

---

OK, 把上面的 path 列出來： (L)

 { "HPOL"           , NULL           , "HP Amp"          },
 { "HP Amp"         , NULL           , "HPO MIX"         },
 { "HPO MIX"        , "DAC1 Switch"  , "DAC 1"           },
 { "DAC 1"          , NULL           , "DAC L1"          },
 { "DAC L1"         , NULL           , "Stereo DAC MIXL" },
 { "Stereo DAC MIXL", "DAC L1 Switch", "DAC1 MIXL"       },
 { "DAC1 MIXL"      , "DAC1 Switch"  , "DAC1 L Mux"      },
 { "DAC1 L Mux"     , "IF1 DAC"      , "IF1 DAC1 L"      },
 { "IF1 DAC1 L"     , NULL           , "IF1 DAC1"        },
 { "IF1 DAC1"       , NULL           , "I2S1"            },
 { "I2S1"           , NULL           , "ASRC enable"     },

其中，中間一項不是 NULL 的，就要寫在 asound.conf 中..

寫的東西要用 tinymixer 來看...
tinymixer 會列出所有的 control gadge..

要設的有...

36 BOOL 1 HPO MIX DAC1 Switch                      On
62 BOOL 1 Stereo DAC MIXR DAC R1 Switch            On
65 BOOL 1 Stereo DAC MIXL DAC L1 Switch            On
73 BOOL 1 DAC1 MIXR DAC1 Switch                    On
75 BOOL 1 DAC1 MIXL DAC1 Switch                    On
68 ENUM 1 DAC1 R Mux                               IF1 DAC
69 ENUM 1 DAC1 L Mux                               IF1 DAC

所以 /etc/asound.conf 就是....