Re: [Qemu-devel] [PATCH v3 1/3] VFIO: Wrapper for getting reference to vfio_device from device

[Alex Williamson]

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 <address@hidden>
> ---
>  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