[Spice-devel] [usbredir PATCH v4 1/2] usbredirhost: new callback for iso streams

[Victor Toso]

For streaming devices it might be necessary from application to drop
data for different reasons. This patch provides a new callback that it
is called before queueing the most recent iso packages.

Related: https://bugzilla.redhat.com/show_bug.cgi?id=1264156
---
 usbredirhost/usbredirhost.c | 70 +++++++++++++++++++++++++++++++++++++++++++--
 usbredirhost/usbredirhost.h | 13 +++++++++
 2 files changed, 81 insertions(+), 2 deletions(-)

diff --git a/usbredirhost/usbredirhost.c b/usbredirhost/usbredirhost.c
index ad30722..1eaa13e 100644
--- a/usbredirhost/usbredirhost.c
+++ b/usbredirhost/usbredirhost.c
@@ -109,6 +109,7 @@ struct usbredirhost {
     usbredirparser_read read_func;
     usbredirparser_write write_func;
     usbredirhost_flush_writes flush_writes_func;
+    usbredirhost_can_write_iso can_write_iso_func;
     void *func_priv;
     int verbose;
     libusb_context *ctx;
@@ -130,6 +131,11 @@ struct usbredirhost {
     struct usbredirtransfer transfers_head;
     struct usbredirfilter_rule *filter_rules;
     int filter_rules_count;
+    struct {
+        uint64_t higher;
+        uint64_t lower;
+        uint64_t packets;
+    } iso_threshold;
 };
 
 struct usbredirhost_dev_ids {
@@ -1003,6 +1009,50 @@ static void usbredirhost_send_stream_status(struct usbredirhost *host,
     }
 }
 
+/* This function should always be called with LOCK in the host */
+static int usbredirhost_can_write_iso_package(struct usbredirhost *host,
+        uint8_t ep)
+{
+    uint64_t size;
+    int can_write_packet = 1;
+
+    if (!host->can_write_iso_func)
+        return can_write_packet;
+
+    size = host->can_write_iso_func(host->func_priv);
+    if (size >= host->iso_threshold.higher) {
+        /* Drop some packages, this one included */
+        can_write_packet = 0;
+        host->endpoint[EP2I(ep)].drop_packets =
+                     (host->endpoint[EP2I(ep)].pkts_per_transfer *
+                      host->endpoint[EP2I(ep)].transfer_count) * 2;
+        goto end;
+    }
+
+    if (size >= host->iso_threshold.lower) {
+        /* While we are in the lower threshold, we drop a fixed interval
+         * of iso packages so client application can keep streaming without
+         * buffering too fast */
+        if (host->iso_threshold.packets == 0) {
+            host->iso_threshold.packets =
+                          (host->endpoint[EP2I(ep)].pkts_per_transfer *
+                           host->endpoint[EP2I(ep)].transfer_count);
+            host->endpoint[EP2I(ep)].drop_packets = host->iso_threshold.packets;
+            can_write_packet = 0;
+        } else {
+            host->iso_threshold.packets--;
+        }
+        goto end;
+    }
+
+    /* In case we were above lower threshold, reset package counter */
+    if (host->iso_threshold.packets != 0) {
+        host->iso_threshold.packets = 0;
+    }
+end:
+    return can_write_packet;
+}
+
 static void usbredirhost_send_stream_data(struct usbredirhost *host,
     uint64_t id, uint8_t ep, uint8_t status, uint8_t *data, int len)
 {
@@ -1028,8 +1078,10 @@ static void usbredirhost_send_stream_data(struct usbredirhost *host,
             .status   = status,
             .length   = len,
         };
-        usbredirparser_send_iso_packet(host->parser, id, &iso_packet,
-                                       data, len);
+
+        if (usbredirhost_can_write_iso_package(host, ep))
+            usbredirparser_send_iso_packet(host->parser, id, &iso_packet,
+                                           data, len);
         break;
     }
     case usb_redir_type_bulk: {
@@ -1358,6 +1410,20 @@ static void usbredirhost_log_data(struct usbredirhost *host, const char *desc,
 
 /**************************************************************************/
 
+void usbredirhost_set_cb_can_write_iso(struct usbredirhost *host,
+    usbredirhost_can_write_iso can_write_iso_func,
+    uint64_t threshold_higher, uint64_t threshold_lower)
+{
+    if (!host) {
+        ERROR("invalid usbredirhost");
+        return;
+    }
+
+    host->can_write_iso_func = can_write_iso_func;
+    host->iso_threshold.higher = threshold_higher;
+    host->iso_threshold.lower = threshold_lower;
+}
+
 /* Return value:
     0 All ok
     1 Packet borked, continue with next packet / urb
diff --git a/usbredirhost/usbredirhost.h b/usbredirhost/usbredirhost.h
index c0042c9..784fefd 100644
--- a/usbredirhost/usbredirhost.h
+++ b/usbredirhost/usbredirhost.h
@@ -33,6 +33,8 @@ struct usbredirhost;
 
 typedef void (*usbredirhost_flush_writes)(void *priv);
 
+typedef uint64_t (*usbredirhost_can_write_iso)(void *priv);
+
 /* This function creates an usbredirhost instance, including its embedded
    libusbredirparser instance and sends the initial usb_redir_hello packet to
    the usb-guest.
@@ -114,6 +116,17 @@ void usbredirhost_close(struct usbredirhost *host);
 int usbredirhost_set_device(struct usbredirhost *host,
                             libusb_device_handle *usb_dev_handle);
 
+/* Call this function to set a callback and two threshold levels in usbredirhost.
+   The usbredirhost_can_write_iso callback should return the application's
+   buffer size (in bytes) that are handling the isochronous data.
+   If the buffer size is between lower and higher threshold, usbredirhost will
+   drop frames before delivering to application; If the buffer size is bigger
+   then maximum threshold, usbredirhost will drop all the frames.
+*/
+void usbredirhost_set_cb_can_write_iso(struct usbredirhost *host,
+    usbredirhost_can_write_iso can_write_iso_func,
+    uint64_t threshold_higher, uint64_t threshold_lower);
+
 /* Call this whenever there is data ready for the usbredirhost to read from
    the usb-guest
    returns 0 on success, or an error code from the below enum on error.
-- 
2.5.0