spice-qemu-char.c: remove intermediate bufferchardev-flowcontrol

BZ: 672191
upstream: not submitted (explained below)

virtio-serial's buffer is valid when it calls us, and we don't
access it otherwise: vmc_read is only called in response to wakeup,
or else we set datalen=0 and throttle. Then vmc_read is called back,
we return 0 (not accessing the buffer) and set the timer to unthrottle.

Also make datalen int and not ssize_t (to fit spice_chr_write signature).

This relied on the previous patch that introduces throttling, which
can't go upstream right now as explained in that patch.

1 files changed, 6 insertions, 12 deletions

diff --git a/spice-qemu-char.c b/spice-qemu-char.c
index 5d48fb49c..c86d2990a 100644
--- a/spice-qemu-char.c
+++ b/spice-qemu-char.c
@@ -23,9 +23,8 @@ typedef struct SpiceCharDriver {
     SpiceCharDeviceInstance     sin;
     char                  *subtype;
     bool                  active;
-    uint8_t               *buffer;
-    uint8_t               *datapos;
-    ssize_t               bufsize, datalen;
+    const uint8_t         *datapos;
+    int                   datalen;
     uint32_t              debug;
     QEMUTimer             *unblock_timer;
 } SpiceCharDriver;
@@ -70,7 +69,7 @@ static int vmc_read(SpiceCharDeviceInstance *sin, uint8_t *buf, int len)
     SpiceCharDriver *scd = container_of(sin, SpiceCharDriver, sin);
     int bytes = MIN(len, scd->datalen);
 
-    dprintf(scd, 2, "%s: %p %d/%d/%zd\n", __func__, scd->datapos, len, bytes, scd->datalen);
+    dprintf(scd, 2, "%s: %p %d/%d/%d\n", __func__, scd->datapos, len, bytes, scd->datalen);
     if (bytes > 0) {
         memcpy(buf, scd->datapos, bytes);
         scd->datapos += bytes;
@@ -133,18 +132,13 @@ static int spice_chr_write(CharDriverState *chr, const uint8_t *buf, int len)
     dprintf(s, 2, "%s: %d\n", __func__, len);
     vmc_register_interface(s);
     assert(s->datalen == 0);
-    if (s->bufsize < len) {
-        s->bufsize = len;
-        s->buffer = qemu_realloc(s->buffer, s->bufsize);
-    }
-    memcpy(s->buffer, buf, len);
-    s->datapos = s->buffer;
+    s->datapos = buf;
     s->datalen = len;
     spice_server_char_device_wakeup(&s->sin);
     read_bytes = len - s->datalen;
     if (read_bytes != len) {
-        dprintf(s, 1, "%s: throttling: %d < %d (%zd)\n", __func__,
-                read_bytes, len, s->bufsize);
+        dprintf(s, 1, "%s: throttling: %d < %d\n", __func__,
+                read_bytes, len);
         s->chr->write_blocked = true;
         /* We'll get passed in the unconsumed data with the next call */
         s->datalen = 0;