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Commit d4024af5 authored by Michael S. Tsirkin's avatar Michael S. Tsirkin
Browse files

virtio: add low-level APIs for feature bits 



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: default avatarMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: default avatarCornelia Huck <cornelia.huck@de.ibm.com>
parent b2776bf7

include/linux/virtio_config.h

+50 −3
Original line number Diff line number Diff line
@@ -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