1 files changed, 44 insertions, 37 deletions

diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index d581b2914b34..50db245c81ad 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -16,27 +16,20 @@
 #define VIRTIO_CONFIG_S_FAILED          0x80
 
 #ifdef __KERNEL__
-struct virtio_device;
+#include <linux/virtio.h>
 
 /**
  * virtio_config_ops - operations for configuring a virtio device
- * @feature: search for a feature in this config
- *      vdev: the virtio_device
- *      bit: the feature bit
- *      Returns true if the feature is supported.  Acknowledges the feature
- *      so the host can see it.
  * @get: read the value of a configuration field
  *      vdev: the virtio_device
  *      offset: the offset of the configuration field
  *      buf: the buffer to write the field value into.
  *      len: the length of the buffer
- *      Note that contents are conventionally little-endian.
  * @set: write the value of a configuration field
  *      vdev: the virtio_device
  *      offset: the offset of the configuration field
  *      buf: the buffer to read the field value from.
  *      len: the length of the buffer
- *      Note that contents are conventionally little-endian.
  * @get_status: read the status byte
  *      vdev: the virtio_device
  *      Returns the status byte
@@ -52,10 +45,15 @@ struct virtio_device;
  *      callback: the virqtueue callback
  *      Returns the new virtqueue or ERR_PTR() (eg. -ENOENT).
  * @del_vq: free a virtqueue found by find_vq().
+ * @get_features: get the array of feature bits for this device.
+ *      vdev: the virtio_device
+ *      Returns the first 32 feature bits (all we currently need).
+ * @set_features: confirm what device features we'll be using.
+ *      vdev: the virtio_device
+ *      feature: the first 32 feature bits
  */
 struct virtio_config_ops
 {
-        bool (*feature)(struct virtio_device *vdev, unsigned bit);
         void (*get)(struct virtio_device *vdev, unsigned offset,
                     void *buf, unsigned len);
         void (*set)(struct virtio_device *vdev, unsigned offset,
@@ -67,43 +65,52 @@ struct virtio_config_ops
                                      unsigned index,
                                      void (*callback)(struct virtqueue *));
         void (*del_vq)(struct virtqueue *vq);
+        u32 (*get_features)(struct virtio_device *vdev);
+        void (*set_features)(struct virtio_device *vdev, u32 features);
 };
 
+/* If driver didn't advertise the feature, it will never appear. */
+void virtio_check_driver_offered_feature(const struct virtio_device *vdev,
+                                         unsigned int fbit);
+
 /**
- * virtio_config_val - look for a feature and get a single virtio config.
- * @vdev: the virtio device
+ * virtio_has_feature - helper to determine if this device has this feature.
+ * @vdev: the device
  * @fbit: the feature bit
- * @offset: the type to search for.
- * @val: a pointer to the value to fill in.
- *
- * The return value is -ENOENT if the feature doesn't exist.  Otherwise
- * the value is endian-corrected and returned in v. */
-#define virtio_config_val(vdev, fbit, offset, v) ({                     \
-        int _err;                                                       \
-        if ((vdev)->config->feature((vdev), (fbit))) {                  \
-                __virtio_config_val((vdev), (offset), (v));             \
-                _err = 0;                                               \
-        } else                                                          \
-                _err = -ENOENT;                                         \
-        _err;                                                           \
-})
+ */
+static inline bool virtio_has_feature(const struct virtio_device *vdev,
+                                      unsigned int fbit)
+{
+        /* Did you forget to fix assumptions on max features? */
+        if (__builtin_constant_p(fbit))
+                BUILD_BUG_ON(fbit >= 32);
+
+        virtio_check_driver_offered_feature(vdev, fbit);
+        return test_bit(fbit, vdev->features);
+}
 
 /**
- * __virtio_config_val - get a single virtio config without feature check.
+ * virtio_config_val - look for a feature and get a virtio config entry.
  * @vdev: the virtio device
+ * @fbit: the feature bit
  * @offset: the type to search for.
  * @val: a pointer to the value to fill in.
  *
- * The value is endian-corrected and returned in v. */
-#define __virtio_config_val(vdev, offset, v) do {                       \
-        BUILD_BUG_ON(sizeof(*(v)) != 1 && sizeof(*(v)) != 2             \
-                     && sizeof(*(v)) != 4 && sizeof(*(v)) != 8);        \
-        (vdev)->config->get((vdev), (offset), (v), sizeof(*(v)));       \
-        switch (sizeof(*(v))) {                                         \
-        case 2: le16_to_cpus((__u16 *) v); break;                       \
-        case 4: le32_to_cpus((__u32 *) v); break;                       \
-        case 8: le64_to_cpus((__u64 *) v); break;                       \
-        }                                                               \
-} while(0)
+ * The return value is -ENOENT if the feature doesn't exist.  Otherwise
+ * the config value is copied into whatever is pointed to by v. */
+#define virtio_config_val(vdev, fbit, offset, v) \
+        virtio_config_buf((vdev), (fbit), (offset), (v), sizeof(v))
+
+static inline int virtio_config_buf(struct virtio_device *vdev,
+                                    unsigned int fbit,
+                                    unsigned int offset,
+                                    void *buf, unsigned len)
+{
+        if (!virtio_has_feature(vdev, fbit))
+                return -ENOENT;
+
+        vdev->config->get(vdev, offset, buf, len);
+        return 0;
+}
 #endif /* __KERNEL__ */
 #endif /* _LINUX_VIRTIO_CONFIG_H */