svn commit: r340248 - head/sys/dev/sound/usb

[Hans Petter Selasky]

Author: hselasky
Date: Thu Nov  8 12:46:47 2018
New Revision: 340248
URL: https://svnweb.freebsd.org/changeset/base/340248

Log:
  Don't read the USB audio sync endpoint when we don't use it to save
  isochronous bandwidth.
  
  MFC after:		3 days
  Sponsored by:		Mellanox Technologies

Modified:
  head/sys/dev/sound/usb/uaudio.c

Modified: head/sys/dev/sound/usb/uaudio.c
==============================================================================
--- head/sys/dev/sound/usb/uaudio.c	Thu Nov  8 12:45:28 2018	(r340247)
+++ head/sys/dev/sound/usb/uaudio.c	Thu Nov  8 12:46:47 2018	(r340248)
@@ -100,7 +100,7 @@ static int uaudio_default_channels = 0;		/* use defaul
 static int uaudio_buffer_ms = 8;
 
 #ifdef USB_DEBUG
-static int uaudio_debug = 0;
+static int uaudio_debug;
 
 static SYSCTL_NODE(_hw_usb, OID_AUTO, uaudio, CTLFLAG_RW, 0, "USB uaudio");
 
@@ -136,6 +136,8 @@ uaudio_buffer_ms_sysctl(SYSCTL_HANDLER_ARGS)
 SYSCTL_PROC(_hw_usb_uaudio, OID_AUTO, buffer_ms, CTLTYPE_INT | CTLFLAG_RWTUN,
     0, sizeof(int), uaudio_buffer_ms_sysctl, "I",
     "uaudio buffering delay from 2ms to 8ms");
+#else
+#define	uaudio_debug 0
 #endif
 
 #define	UAUDIO_NFRAMES		64	/* must be factor of 8 due HS-USB */
@@ -2161,6 +2163,14 @@ uaudio_chan_play_sync_callback(struct usb_xfer *xfer, 
 		break;
 
 	case USB_ST_SETUP:
+		/*
+		 * Check if the recording stream can be used as a
+		 * source of jitter information to save some
+		 * isochronous bandwidth:
+		 */
+		if (ch->priv_sc->sc_rec_chan.num_alt != 0 &&
+		    uaudio_debug == 0)
+			break;
 		usbd_xfer_set_frames(xfer, 1);
 		usbd_xfer_set_frame_len(xfer, 0, usbd_xfer_max_framelen(xfer));
 		usbd_transfer_submit(xfer);