Patchwork [19/20] virtio: console: add flow control

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Submitter Amit Shah
Date March 5, 2013, 5:51 p.m.
Message ID <abffa02235d55ca6e2489068c58971c8897e976c.1362505276.git.amit.shah@redhat.com>
Download mbox | patch
Permalink /patch/225137/
State New
Headers show

Comments

Amit Shah - March 5, 2013, 5:51 p.m.
The virtio-serial-bus already has the logic to make flow control work
properly.  Hook into the char layer's new ability to signal a backend is
writable again.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
---
 hw/virtio-console.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

Patch

diff --git a/hw/virtio-console.c b/hw/virtio-console.c
index 46072a0..b3ee074 100644
--- a/hw/virtio-console.c
+++ b/hw/virtio-console.c
@@ -20,6 +20,18 @@  typedef struct VirtConsole {
     CharDriverState *chr;
 } VirtConsole;
 
+/*
+ * Callback function that's called from chardevs when backend becomes
+ * writable.
+ */
+static gboolean chr_write_unblocked(GIOChannel *chan, GIOCondition cond,
+                                    void *opaque)
+{
+    VirtConsole *vcon = opaque;
+
+    virtio_serial_throttle_port(&vcon->port, false);
+    return FALSE;
+}
 
 /* Callback function that's called when the guest sends us data */
 static ssize_t flush_buf(VirtIOSerialPort *port, const uint8_t *buf, size_t len)
@@ -48,6 +60,7 @@  static ssize_t flush_buf(VirtIOSerialPort *port, const uint8_t *buf, size_t len)
          * do_flush_queued_data().
          */
         ret = 0;
+        qemu_chr_fe_add_watch(vcon->chr, G_IO_OUT, chr_write_unblocked, vcon);
     }
     return ret;
 }