[PATCH v7 01/46] virtio: add low-level APIs for feature bits

Michael S. Tsirkin
2014-11-30T15:09:30Z

Add low level APIs to test/set/clear feature bits.
For use by transports, to make it easier to
write code independent of feature bit array format.

Note: APIs is prefixed with __ and has _bit suffix
to stress its low level nature. It's for use by transports only:
drivers should use virtio_has_feature and never need to set/clear
features.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
include/linux/virtio_config.h | 53 ++++++++++++++++++++++++++++++++++++++++---
1 file changed, 50 insertions(+), 3 deletions(-)

diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index 7f4ef66..d8e28a2 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -77,11 +77,47 @@ void virtio_check_driver_offered_feature(const struct virtio_device *vdev,
unsigned int fbit);

/**
- * virtio_has_feature - helper to determine if this device has this feature.
+ * __virtio_test_bit - helper to test feature bits. For use by transports.
+ * Devices should normally use virtio_has_feature,
+ * which includes more checks.
* @vdev: the device
* @fbit: the feature bit
*/
-static inline bool virtio_has_feature(const struct virtio_device *vdev,
+static inline bool __virtio_test_bit(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);
+ else
+ BUG_ON(fbit >= 32);
+
+ return test_bit(fbit, vdev->features);
+}
+
+/**
+ * __virtio_set_bit - helper to set feature bits. For use by transports.
+ * @vdev: the device
+ * @fbit: the feature bit
+ */
+static inline void __virtio_set_bit(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);
+ else
+ BUG_ON(fbit >= 32);
+
+ set_bit(fbit, vdev->features);
+}
+
+/**
+ * __virtio_clear_bit - helper to clear feature bits. For use by transports.
+ * @vdev: the device
+ * @fbit: the feature bit
+ */
+static inline void __virtio_clear_bit(struct virtio_device *vdev,
unsigned int fbit)
{
/* Did you forget to fix assumptions on max features? */
@@ -90,10 +126,21 @@ static inline bool virtio_has_feature(const struct virtio_device *vdev,
else
BUG_ON(fbit >= 32);

+ clear_bit(fbit, vdev->features);
+}
+
+/**
+ * virtio_has_feature - helper to determine if this device has this feature.
+ * @vdev: the device
+ * @fbit: the feature bit
+ */
+static inline bool virtio_has_feature(const struct virtio_device *vdev,
+ unsigned int fbit)
+{
if (fbit < VIRTIO_TRANSPORT_F_START)
virtio_check_driver_offered_feature(vdev, fbit);

- return test_bit(fbit, vdev->features);
+ return __virtio_test_bit(vdev, fbit);
}

static inline
--
MST