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virtio: add low-level APIs for feature bits

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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>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
This commit is contained in:
Michael S. Tsirkin 2014-11-27 21:19:02 +02:00
parent b2776bf714
commit d4024af56f
1 changed files with 50 additions and 3 deletions
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53
include/linux/virtio_config.h
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@ -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