virtio: explicit advertisement of driver features
A recent proposed feature addition to the virtio block driver revealed
some flaws in the API: in particular, we assume that feature
negotiation is complete once a driver's probe function returns.
There is nothing in the API to require this, however, and even I
didn't notice when it was violated.
So instead, we require the driver to specify what features it supports
in a table, we can then move the feature negotiation into the virtio
core. The intersection of device and driver features are presented in
a new 'features' bitmap in the struct virtio_device.
Note that this highlights the difference between Linux unsigned-long
bitmaps where each unsigned long is in native endian, and a
straight-forward little-endian array of bytes.
Drivers can still remove feature bits in their probe routine if they
really have to.
API changes:
- dev->config->feature() no longer gets and acks a feature.
- drivers should advertise their features in the 'feature_table' field
- use virtio_has_feature() for extra sanity when checking feature bits
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index ad43421..f926b5a 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -378,26 +378,26 @@
SET_NETDEV_DEV(dev, &vdev->dev);
/* Do we support "hardware" checksums? */
- if (csum && vdev->config->feature(vdev, VIRTIO_NET_F_CSUM)) {
+ if (csum && virtio_has_feature(vdev, VIRTIO_NET_F_CSUM)) {
/* This opens up the world of extra features. */
dev->features |= NETIF_F_HW_CSUM|NETIF_F_SG|NETIF_F_FRAGLIST;
- if (gso && vdev->config->feature(vdev, VIRTIO_NET_F_GSO)) {
+ if (gso && virtio_has_feature(vdev, VIRTIO_NET_F_GSO)) {
dev->features |= NETIF_F_TSO | NETIF_F_UFO
| NETIF_F_TSO_ECN | NETIF_F_TSO6;
}
/* Individual feature bits: what can host handle? */
- if (gso && vdev->config->feature(vdev, VIRTIO_NET_F_HOST_TSO4))
+ if (gso && virtio_has_feature(vdev, VIRTIO_NET_F_HOST_TSO4))
dev->features |= NETIF_F_TSO;
- if (gso && vdev->config->feature(vdev, VIRTIO_NET_F_HOST_TSO6))
+ if (gso && virtio_has_feature(vdev, VIRTIO_NET_F_HOST_TSO6))
dev->features |= NETIF_F_TSO6;
- if (gso && vdev->config->feature(vdev, VIRTIO_NET_F_HOST_ECN))
+ if (gso && virtio_has_feature(vdev, VIRTIO_NET_F_HOST_ECN))
dev->features |= NETIF_F_TSO_ECN;
- if (gso && vdev->config->feature(vdev, VIRTIO_NET_F_HOST_UFO))
+ if (gso && virtio_has_feature(vdev, VIRTIO_NET_F_HOST_UFO))
dev->features |= NETIF_F_UFO;
}
/* Configuration may specify what MAC to use. Otherwise random. */
- if (vdev->config->feature(vdev, VIRTIO_NET_F_MAC)) {
+ if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC)) {
vdev->config->get(vdev,
offsetof(struct virtio_net_config, mac),
dev->dev_addr, dev->addr_len);
@@ -486,7 +486,15 @@
{ 0 },
};
+static unsigned int features[] = {
+ VIRTIO_NET_F_CSUM, VIRTIO_NET_F_GSO, VIRTIO_NET_F_MAC,
+ VIRTIO_NET_F_HOST_TSO4, VIRTIO_NET_F_HOST_UFO, VIRTIO_NET_F_HOST_TSO6,
+ VIRTIO_NET_F_HOST_ECN,
+};
+
static struct virtio_driver virtio_net = {
+ .feature_table = features,
+ .feature_table_size = ARRAY_SIZE(features),
.driver.name = KBUILD_MODNAME,
.driver.owner = THIS_MODULE,
.id_table = id_table,