On Fri, Nov 28, 2014 at 11:02:20AM +0100, Cornelia Huck wrote:
> On Thu, 27 Nov 2014 22:07:36 +0200
> "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote:
>
> > 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.
> >
> > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> > ---
> > 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..249fcd6 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);
>
> Does this want to be a helper? Might be overkill, but I'm always wary
> of changes that need to be applied manually in many different places :)
I'm not sure. It's just an assert, if it's not obvious
what it checks then it doesn't serve a useful purpose.
> > +
> > + 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 set feature bits. For use by transports.
>
> s/set/clear/
Good catch, thanks.
> > + * @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
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