[PATCH 3/5 ver2] virtio: Fix non-const BUILD_BUG_ON usage

[Boaz Harrosh <bharrosh@panasas.com>]

In virtio_has_feature() BUILD_BUG_ON can not be used cross inline
parametrization boundary. I've put the BUILD_BUG_ON(_ZERO) in a
macro outside of the inline definition. (So it is in the caller scope).

However It is no longer legal to pass BUILD_BUG_ON a non-const
expression so users like virtio_config_buf() should caller
__virtio_has_feature() which does the actual code minus the
check.

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
CC: Ingo Molnar <mingo@elte.hu>
CC: Rusty Russell <rusty@rustcorp.com.au>
---
 include/linux/virtio_config.h |   13 +++++++------
 1 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index bf8ec28..7accb1d 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -92,17 +92,18 @@ void virtio_check_driver_offered_feature(const struct virtio_device *vdev,
  * @vdev: the device
  * @fbit: the feature bit
  */
-static inline bool virtio_has_feature(const struct virtio_device *vdev,
+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);
 }
 
+/* Did you forget to fix assumptions on max features? */
+#define virtio_has_feature(vdev, fbit) \
+	(BUILD_BUG_ON_ZERO(fbit >= 32) + __virtio_has_feature(vdev, fbit))
+	
+
 /**
  * virtio_config_val - look for a feature and get a virtio config entry.
  * @vdev: the virtio device
@@ -120,7 +121,7 @@ static inline int virtio_config_buf(struct virtio_device *vdev,
 				    unsigned int offset,
 				    void *buf, unsigned len)
 {
-	if (!virtio_has_feature(vdev, fbit))
+	if (!__virtio_has_feature(vdev, fbit))
 		return -ENOENT;
 
 	vdev->config->get(vdev, offset, buf, len);
-- 
1.5.6.rc1.5.gadf6