virtio: allow drivers to validate features

Some drivers can't support all features in all configurations.  At the
moment we blindly set FEATURES_OK and later FAILED.  Support this better
by adding a callback drivers can use to do some early checks.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 400d70b6937948cc5a8aac698efc64fcf49c1dde..48230a5e12f262b67d28d87adc713f462e8ec5fc 100644 (file)
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -232,6 +232,12 @@ static int virtio_dev_probe(struct device *_d)
                if (device_features & (1ULL << i))
                        __virtio_set_bit(dev, i);
 
+       if (drv->validate) {
+               err = drv->validate(dev);
+               if (err)
+                       goto err;
+       }
+
        err = virtio_finalize_features(dev);
        if (err)
                goto err;

diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 04b0d3f95043c66856c6a6f4cab078c4791d35e8..7edfbdb55a995d436bf9e999ce202d0ca0bf2550 100644 (file)
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -167,6 +167,7 @@ struct virtio_driver {
        unsigned int feature_table_size;
        const unsigned int *feature_table_legacy;
        unsigned int feature_table_size_legacy;
+       int (*validate)(struct virtio_device *dev);
        int (*probe)(struct virtio_device *dev);
        void (*scan)(struct virtio_device *dev);
        void (*remove)(struct virtio_device *dev);