wm8731: document audiohw settings

Change-Id: I78ec26a00a3e14a95c591ac81d96e1b480b9138e

2 files changed, 4 insertions, 2 deletions

diff --git a/firmware/drivers/audio/wm8731.c b/firmware/drivers/audio/wm8731.c
index 18e04618bf..98155a71eb 100644
--- a/firmware/drivers/audio/wm8731.c
+++ b/firmware/drivers/audio/wm8731.c
@@ -268,6 +268,8 @@ void audiohw_disable_recording(void)
     codec_set_active(true);
 }
 
+/* Line in: 0 .. 31 => Volume -34.5 .. +12 dB
+ * Microphone: 0 or 20 dB */
 void audiohw_set_recvol(int left, int right, int type)
 {
     switch (type)
diff --git a/firmware/export/wm8731.h b/firmware/export/wm8731.h
index 10925880c3..a725a87484 100644
--- a/firmware/export/wm8731.h
+++ b/firmware/export/wm8731.h
@@ -28,10 +28,10 @@
 
 AUDIOHW_SETTING(VOLUME,     "dB", 0,  1, -74,   6, -25)
 #if defined(HAVE_WM8731) && defined(HAVE_RECORDING)
-/* (x - 23)/1.5 *10 */
+/* Line in: 0 .. 31 => Volume -34.5 .. +12 dB */
 AUDIOHW_SETTING(LEFT_GAIN,  "dB", 1,  1,   0,  31,  23, (val - 23) * 15)
 AUDIOHW_SETTING(RIGHT_GAIN, "dB", 1,  1,   0,  31,  23, (val - 23) * 15)
-/* 0 or 20 dB */
+/* Microphone: 0 or 20 dB */
 AUDIOHW_SETTING(MIC_GAIN,   "dB", 1,  1,   0,   1,   0, val * 200)
 #endif /* defined(HAVE_WM8731) && defined(HAVE_RECORDING) */