use NULL for function pointer init in virtio devs

[Dave Voutila]

While hunting a perf issue with vmd's vioblk emulation, stumbled upon
some virtio drivers initializing function pointers to 0 for their config
change handlers. Switch to using NULL for better semantic fit.

ok?


diff refs/heads/master refs/heads/virtio
commit - 2287d13a721783c23c3036e2df45e2d342fd91bb
commit + 0c7315d2bd9aaa357462913d5bb7bfa2794174cf
blob - b926725a85d27a05db1f1dde90fe99fd2674e651
blob + 354c01a392b02e76f0a2c3c17b9cff294aeb4f86
--- sys/dev/pv/if_vio.c
+++ sys/dev/pv/if_vio.c
@@ -529,7 +529,7 @@ vio_attach(struct device *parent, struct device *self,
        vsc->sc_child = self;
        vsc->sc_ipl = IPL_NET;
        vsc->sc_vqs = &sc->sc_vq[0];
-       vsc->sc_config_change = 0;
+       vsc->sc_config_change = NULL;
        vsc->sc_driver_features = VIRTIO_NET_F_MAC | VIRTIO_NET_F_STATUS |
            VIRTIO_NET_F_CTRL_VQ | VIRTIO_NET_F_CTRL_RX |
            VIRTIO_NET_F_MRG_RXBUF | VIRTIO_NET_F_CSUM |
blob - 2a8d2677848a2f758acbdc5aa7463832d2521718
blob + 0aae4f2a93a3509bae94e010b5fca5ad14f53fc0
--- sys/dev/pv/vioblk.c
+++ sys/dev/pv/vioblk.c
@@ -174,7 +174,7 @@ vioblk_attach(struct device *parent, struct device *se

        vsc->sc_vqs = &sc->sc_vq[0];
        vsc->sc_nvqs = 1;
-       vsc->sc_config_change = 0;
+       vsc->sc_config_change = NULL;
        if (vsc->sc_child)
                panic("already attached to something else");
        vsc->sc_child = self;
blob - 4d154c34bf76de937fa96c3686c124463e8705a1
blob + ac03b17519753d7af5e04eeb0ebb8bf40149877e
--- sys/dev/pv/viocon.c
+++ sys/dev/pv/viocon.c
@@ -180,7 +180,7 @@ viocon_attach(struct device *parent, struct device *se
                panic("already attached to something else");
        vsc->sc_child = self;
        vsc->sc_ipl = IPL_TTY;
-       vsc->sc_config_change = 0;
+       vsc->sc_config_change = NULL;
        sc->sc_virtio = vsc;
        sc->sc_max_ports = maxports;

blob - eb129743be7e06d59e6ebee20e418781c08c8500
blob + 167086980126f3d1535d139e89c962525dcaaed4
--- sys/dev/pv/viornd.c
+++ sys/dev/pv/viornd.c
@@ -88,7 +88,7 @@ viornd_attach(struct device *parent, struct device *se

        vsc->sc_vqs = &sc->sc_vq;
        vsc->sc_nvqs = 1;
-       vsc->sc_config_change = 0;
+       vsc->sc_config_change = NULL;
        if (vsc->sc_child != NULL)
                panic("already attached to something else");
        vsc->sc_child = self;