audio: basic support for multichannel audio

Which currently only means removing some checks.  Old code won't require
more than two channels, but new code will need it.

Signed-off-by: Kővágó, Zoltán <DirtY.iCE.hu@gmail.com>
Message-id: 7e53be1f97e939ed3bb729ef39e76b775643118a.1570996490.git.DirtY.iCE.hu@gmail.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

audio/alsaaudio.c

@@ -493,13 +493,6 @@ static int alsa_open(bool in, struct alsa_params_req *req,
         goto err;
     }
 
-    if (nchannels != 1 && nchannels != 2) {
-        alsa_logerr2 (err, typ,
-                      "Can not handle obtained number of channels %d\n",
-                      nchannels);
-        goto err;
-    }
-
     if (apdo->buffer_length) {
         int dir = 0;
         unsigned int btime = apdo->buffer_length;

audio/audio.c

@@ -242,7 +242,7 @@ static int audio_validate_settings (struct audsettings *as)
 {
     int invalid;
 
-    invalid = as->nchannels != 1 && as->nchannels != 2;
+    invalid = as->nchannels < 1;
     invalid |= as->endianness != 0 && as->endianness != 1;
 
     switch (as->fmt) {