Make dmix card-specific

The parameters of dmix PCM definition are now card-specific.
As default, period_size = 1024 and periods = 8 are used.

src/conf/pcm/dmix.conf

@@ -0,0 +1,85 @@
+#
+# dmix output
+#
+
+pcm.!dmix {
+	@args [ CARD DEV SUBDEV FORMAT RATE ]
+	@args.CARD {
+		type string
+		default 0
+	}
+	@args.DEV {
+		type string
+		default 0
+	}
+	@args.SUBDEV {
+		type string
+		default -1
+	}
+	@args.FORMAT {
+		type string
+		default S16_LE
+	}
+	@args.RATE {
+		type integer
+		default 48000
+	}
+	type dmix
+	ipc_key 5678293
+	ipc_key_add_uid yes
+	slave {
+		pcm {
+			type hw
+			card $CARD
+			device $DEV
+			subdevice $SUBDEV
+		}
+		format $FORMAT
+		rate $RATE
+		period_size {
+			@func refer
+			name {
+				@func concat
+				strings [
+					"cards."
+					{
+						@func card_driver
+						card $CARD
+					}
+					".pcm.dmix.period_size"
+				]
+			}
+			default 1048
+		}		
+		period_time {
+			@func refer
+			name {
+				@func concat
+				strings [
+					"cards."
+					{
+						@func card_driver
+						card $CARD
+					}
+					".pcm.dmix.period_time"
+				]
+			}
+			default -1
+		}		
+		periods {
+			@func refer
+			name {
+				@func concat
+				strings [
+					"cards."
+					{
+						@func card_driver
+						card $CARD
+					}
+					".pcm.dmix.periods"
+				]
+			}
+			default 8
+		}
+	}
+}