virtio: explicit advertisement of driver features

[linux-2.6-omap-h63xx.git] / drivers / virtio / virtio.c

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index b535483bc556f5f153eb434583c8dc6593377164..13866789b3561027b803797a95c985f573671fd4 100644 (file)
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -80,19 +80,51 @@ static void add_status(struct virtio_device *dev, unsigned status)
        dev->config->set_status(dev, dev->config->get_status(dev) | status);
 }
 
+void virtio_check_driver_offered_feature(const struct virtio_device *vdev,
+                                        unsigned int fbit)
+{
+       unsigned int i;
+       struct virtio_driver *drv = container_of(vdev->dev.driver,
+                                                struct virtio_driver, driver);
+
+       for (i = 0; i < drv->feature_table_size; i++)
+               if (drv->feature_table[i] == fbit)
+                       return;
+       BUG();
+}
+EXPORT_SYMBOL_GPL(virtio_check_driver_offered_feature);
+
 static int virtio_dev_probe(struct device *_d)
 {
-       int err;
+       int err, i;
        struct virtio_device *dev = container_of(_d,struct virtio_device,dev);
        struct virtio_driver *drv = container_of(dev->dev.driver,
                                                 struct virtio_driver, driver);
+       u32 device_features;
 
+       /* We have a driver! */
        add_status(dev, VIRTIO_CONFIG_S_DRIVER);
+
+       /* Figure out what features the device supports. */
+       device_features = dev->config->get_features(dev);
+
+       /* Features supported by both device and driver into dev->features. */
+       memset(dev->features, 0, sizeof(dev->features));
+       for (i = 0; i < drv->feature_table_size; i++) {
+               unsigned int f = drv->feature_table[i];
+               BUG_ON(f >= 32);
+               if (device_features & (1 << f))
+                       set_bit(f, dev->features);
+       }
+
        err = drv->probe(dev);
        if (err)
                add_status(dev, VIRTIO_CONFIG_S_FAILED);
-       else
+       else {
                add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
+               /* They should never have set feature bits beyond 32 */
+               dev->config->set_features(dev, dev->features[0]);
+       }
        return err;
 }
 
@@ -114,6 +146,8 @@ static int virtio_dev_remove(struct device *_d)
 
 int register_virtio_driver(struct virtio_driver *driver)
 {
+       /* Catch this early. */
+       BUG_ON(driver->feature_table_size && !driver->feature_table);
        driver->driver.bus = &virtio_bus;
        driver->driver.probe = virtio_dev_probe;
        driver->driver.remove = virtio_dev_remove;