[ALSA] cmipci: document 'Modem' control version check

Add a comment that explains why the 'Modem' control doesn't work with
newer chips.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

1 files changed, 4 insertions, 0 deletions

diff --git a/sound/pci/cmipci.c b/sound/pci/cmipci.c
index 8cb3436d0d9c..bc0a1959f920 100644
--- a/sound/pci/cmipci.c
+++ b/sound/pci/cmipci.c
@@ -2733,6 +2733,10 @@ static int __devinit snd_cmipci_mixer_new(struct cmipci *cm, int pcm_spdif_devic
         }
 
         /* card switches */
+        /*
+         * newer chips don't have the register bits to force modem link
+         * detection; the bit that was FLINKON now mutes CH1
+         */
         if (cm->chip_version < 39) {
                 err = snd_ctl_add(cm->card,
                                   snd_ctl_new1(&snd_cmipci_modem_switch, cm));