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SubjectRe: [PATCH v3 1/3] VFIO: Wrapper for getting reference to vfio_device from device
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On Sun, 2013-02-03 at 14:10 +0000, Pandarathil, Vijaymohan R wrote:
> - Added vfio_device_get_from_dev() as wrapper to get
> reference to vfio_device from struct device.
>
> - Added vfio_device_data() as a wrapper to get device_data from
> vfio_device.
>
> Signed-off-by: Vijay Mohan Pandarathil <vijaymohan.pandarathil@hp.com>
> ---
> drivers/vfio/vfio.c | 41 ++++++++++++++++++++++++++++++++---------
> include/linux/vfio.h | 3 +++
> 2 files changed, 35 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index 12c264d..f0a78a2 100644
> --- a/drivers/vfio/vfio.c
> +++ b/drivers/vfio/vfio.c
> @@ -407,12 +407,13 @@ static void vfio_device_release(struct kref *kref)
> }
>
> /* Device reference always implies a group reference */
> -static void vfio_device_put(struct vfio_device *device)
> +void vfio_device_put(struct vfio_device *device)
> {
> struct vfio_group *group = device->group;
> kref_put_mutex(&device->kref, vfio_device_release, &group->device_lock);
> vfio_group_put(group);
> }
> +EXPORT_SYMBOL_GPL(vfio_device_put);
>
> static void vfio_device_get(struct vfio_device *device)
> {
> @@ -642,8 +643,12 @@ int vfio_add_group_dev(struct device *dev,
> }
> EXPORT_SYMBOL_GPL(vfio_add_group_dev);
>
> -/* Test whether a struct device is present in our tracking */
> -static bool vfio_dev_present(struct device *dev)
> +/**
> + * This does a get on the vfio_device from device.
> + * Callers of this function will have to call vfio_put_device() to
> + * remove the reference.
> + */
> +struct vfio_device *vfio_device_get_from_dev(struct device *dev)
> {
> struct iommu_group *iommu_group;
> struct vfio_group *group;
> @@ -651,25 +656,43 @@ static bool vfio_dev_present(struct device *dev)
>
> iommu_group = iommu_group_get(dev);
> if (!iommu_group)
> - return false;
> + return NULL;
>
> group = vfio_group_get_from_iommu(iommu_group);
> if (!group) {
> iommu_group_put(iommu_group);
> - return false;
> + return NULL;
> }
>
> device = vfio_group_get_device(group, dev);
> if (!device) {
> vfio_group_put(group);
> iommu_group_put(iommu_group);
> - return false;
> + return NULL;

nit, this test isn't necesary, skipping the whole if block and falling
through to the return below is functionally the same.

> }
> -
> - vfio_device_put(device);
> vfio_group_put(group);
> iommu_group_put(iommu_group);
> - return true;
> + return device;
> +}
> +EXPORT_SYMBOL_GPL(vfio_device_get_from_dev);
> +

Let's add a comment here that the caller must hold a reference to the
vfio_device. Thanks,

Alex

> +void *vfio_device_data(struct vfio_device *device)
> +{
> + return device->device_data;
> +}
> +EXPORT_SYMBOL_GPL(vfio_device_data);
> +
> +/* Test whether a struct device is present in our tracking */
> +static bool vfio_dev_present(struct device *dev)
> +{
> + struct vfio_device *device;
> +
> + device = vfio_device_get_from_dev(dev);
> + if (device) {
> + vfio_device_put(device);
> + return true;
> + } else
> + return false;
> }
>
> /*
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index ab9e862..ac8d488 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -45,6 +45,9 @@ extern int vfio_add_group_dev(struct device *dev,
> void *device_data);
>
> extern void *vfio_del_group_dev(struct device *dev);
> +extern struct vfio_device *vfio_device_get_from_dev(struct device *dev);
> +extern void vfio_device_put(struct vfio_device *device);
> +extern void *vfio_device_data(struct vfio_device *device);
>
> /**
> * struct vfio_iommu_driver_ops - VFIO IOMMU driver callbacks





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