[Xen-devel] [PATCH 06/12] xen: make use of xenbus_read_unsigned() in xen-netback

[Juergen Gross <jgross@xxxxxxxx>]

Use xenbus_read_unsigned() instead of xenbus_scanf() when possible.
This requires to change the type of some reads from int to unsigned,
but these cases have been wrong before: negative values are not allowed
for the modified cases.

Cc: wei.liu2@xxxxxxxxxx
Cc: paul.durrant@xxxxxxxxxx
Cc: netdev@xxxxxxxxxxxxxxx

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 drivers/net/xen-netback/xenbus.c | 50 +++++++++++-----------------------------
 1 file changed, 14 insertions(+), 36 deletions(-)

diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
index 8674e18..7356e00 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c
@@ -785,12 +785,9 @@ static void xen_mcast_ctrl_changed(struct xenbus_watch 
*watch,
        struct xenvif *vif = container_of(watch, struct xenvif,
                                          mcast_ctrl_watch);
        struct xenbus_device *dev = xenvif_to_xenbus_device(vif);
-       int val;
 
-       if (xenbus_scanf(XBT_NIL, dev->otherend,
-                        "request-multicast-control", "%d", &val) < 0)
-               val = 0;
-       vif->multicast_control = !!val;
+       vif->multicast_control = !!xenbus_read_unsigned(dev->otherend,
+                                       "request-multicast-control", 0);
 }
 
 static int xen_register_mcast_ctrl_watch(struct xenbus_device *dev,
@@ -934,12 +931,9 @@ static void connect(struct backend_info *be)
        /* Check whether the frontend requested multiple queues
         * and read the number requested.
         */
-       err = xenbus_scanf(XBT_NIL, dev->otherend,
-                          "multi-queue-num-queues",
-                          "%u", &requested_num_queues);
-       if (err < 0) {
-               requested_num_queues = 1; /* Fall back to single queue */
-       } else if (requested_num_queues > xenvif_max_queues) {
+       requested_num_queues = xenbus_read_unsigned(dev->otherend,
+                                       "multi-queue-num-queues", 1);
+       if (requested_num_queues > xenvif_max_queues) {
                /* buggy or malicious guest */
                xenbus_dev_fatal(dev, err,
                                 "guest requested %u queues, exceeding the 
maximum of %u.",
@@ -1134,7 +1128,7 @@ static int read_xenbus_vif_flags(struct backend_info *be)
        struct xenvif *vif = be->vif;
        struct xenbus_device *dev = be->dev;
        unsigned int rx_copy;
-       int err, val;
+       int err;
 
        err = xenbus_scanf(XBT_NIL, dev->otherend, "request-rx-copy", "%u",
                           &rx_copy);
@@ -1150,10 +1144,7 @@ static int read_xenbus_vif_flags(struct backend_info *be)
        if (!rx_copy)
                return -EOPNOTSUPP;
 
-       if (xenbus_scanf(XBT_NIL, dev->otherend,
-                        "feature-rx-notify", "%d", &val) < 0)
-               val = 0;
-       if (!val) {
+       if (!xenbus_read_unsigned(dev->otherend, "feature-rx-notify", 0)) {
                /* - Reduce drain timeout to poll more frequently for
                 *   Rx requests.
                 * - Disable Rx stall detection.
@@ -1162,34 +1153,21 @@ static int read_xenbus_vif_flags(struct backend_info 
*be)
                be->vif->stall_timeout = 0;
        }
 
-       if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-sg",
-                        "%d", &val) < 0)
-               val = 0;
-       vif->can_sg = !!val;
+       vif->can_sg = !!xenbus_read_unsigned(dev->otherend, "feature-sg", 0);
 
        vif->gso_mask = 0;
 
-       if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv4",
-                        "%d", &val) < 0)
-               val = 0;
-       if (val)
+       if (xenbus_read_unsigned(dev->otherend, "feature-gso-tcpv4", 0))
                vif->gso_mask |= GSO_BIT(TCPV4);
 
-       if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv6",
-                        "%d", &val) < 0)
-               val = 0;
-       if (val)
+       if (xenbus_read_unsigned(dev->otherend, "feature-gso-tcpv6", 0))
                vif->gso_mask |= GSO_BIT(TCPV6);
 
-       if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-no-csum-offload",
-                        "%d", &val) < 0)
-               val = 0;
-       vif->ip_csum = !val;
+       vif->ip_csum = !xenbus_read_unsigned(dev->otherend,
+                                            "feature-no-csum-offload", 0);
 
-       if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-ipv6-csum-offload",
-                        "%d", &val) < 0)
-               val = 0;
-       vif->ipv6_csum = !!val;
+       vif->ipv6_csum = !!xenbus_read_unsigned(dev->otherend,
+                                               "feature-ipv6-csum-offload", 0);
 
        return 0;
 }
-- 
2.6.6


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