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authorRusty Russell <rusty@rustcorp.com.au>2008-05-02 21:50:50 -0500
committerRusty Russell <rusty@rustcorp.com.au>2008-05-02 21:50:50 +1000
commitc45a6816c19dee67b8f725e6646d428901a6dc24 (patch)
tree096e3263fd14e140685bcc3082394ff15f5aeddb /drivers/virtio/virtio_balloon.c
parent72e61eb40b55dd57031ec5971e810649f82b0259 (diff)
downloadvexpress-lsk-c45a6816c19dee67b8f725e6646d428901a6dc24.tar.gz
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>
Diffstat (limited to 'drivers/virtio/virtio_balloon.c')
-rw-r--r--drivers/virtio/virtio_balloon.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index fef88d84cef..bfef604160d 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -227,7 +227,7 @@ static int virtballoon_probe(struct virtio_device *vdev)
}
vb->tell_host_first
- = vdev->config->feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
+ = virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
return 0;
@@ -259,7 +259,11 @@ static void virtballoon_remove(struct virtio_device *vdev)
kfree(vb);
}
+static unsigned int features[] = { VIRTIO_BALLOON_F_MUST_TELL_HOST };
+
static struct virtio_driver virtio_balloon = {
+ .feature_table = features,
+ .feature_table_size = ARRAY_SIZE(features),
.driver.name = KBUILD_MODNAME,
.driver.owner = THIS_MODULE,
.id_table = id_table,