Re: [RFC 1/3] VFIO: platform: add reset support

[Alex Williamson <alex.williamson@redhat.com>]

On Fri, 2015-04-17 at 15:37 +0200, Eric Auger wrote:
> This patch adds support for vfio platform reset. The modality only is
> exposed when a specialized VFIO driver populates the reset callback.
> For the generic vfio platform/amba driver, the modality is not supported
> since the driver is by essence a metadriver and does not know how to
> reset the underlying device.
> 
> Signed-off-by: Eric Auger <eric.auger@linaro.org>
> ---
>  drivers/vfio/platform/vfio_platform_common.c  | 12 ++++++++++--
>  drivers/vfio/platform/vfio_platform_private.h |  1 +
>  2 files changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/vfio/platform/vfio_platform_common.c b/drivers/vfio/platform/vfio_platform_common.c
> index 4113d46..b989ce5 100644
> --- a/drivers/vfio/platform/vfio_platform_common.c
> +++ b/drivers/vfio/platform/vfio_platform_common.c
> @@ -100,6 +100,8 @@ static void vfio_platform_release(void *device_data)
>  	mutex_lock(&driver_lock);
>  
>  	if (!(--vdev->refcnt)) {
> +		if (vdev->reset)
> +			vdev->reset(vdev);
>  		vfio_platform_regions_cleanup(vdev);
>  		vfio_platform_irq_cleanup(vdev);
>  	}
> @@ -159,6 +161,8 @@ static long vfio_platform_ioctl(void *device_data,
>  		if (info.argsz < minsz)
>  			return -EINVAL;
>  
> +		if (vdev->reset)
> +			vdev->flags |= VFIO_DEVICE_FLAGS_RESET;
>  		info.flags = vdev->flags;
>  		info.num_regions = vdev->num_regions;
>  		info.num_irqs = vdev->num_irqs;
> @@ -252,8 +256,12 @@ static long vfio_platform_ioctl(void *device_data,
>  
>  		return ret;
>  
> -	} else if (cmd == VFIO_DEVICE_RESET)
> -		return -EINVAL;
> +	} else if (cmd == VFIO_DEVICE_RESET) {
> +		if (vdev->reset)
> +			return vdev->reset(vdev);
> +		else
> +			return -ENOTTY;

nit, this should probably still return -EINVAL.  The ioctl is there, but
it's unsupported for this device as the user should have learned from
the above flags.  It's therefore not lack of an ioctl, but invalid use
of an ioctl.

> +	}
>  
>  	return -ENOTTY;
>  }
> diff --git a/drivers/vfio/platform/vfio_platform_private.h b/drivers/vfio/platform/vfio_platform_private.h
> index 253caa3..0a20028 100644
> --- a/drivers/vfio/platform/vfio_platform_private.h
> +++ b/drivers/vfio/platform/vfio_platform_private.h
> @@ -68,6 +68,7 @@ struct vfio_platform_device {
>  	struct resource*
>  		(*get_resource)(struct vfio_platform_device *vdev, int i);
>  	int	(*get_irq)(struct vfio_platform_device *vdev, int i);
> +	int	(*reset)(struct vfio_platform_device *vdev);
>  };
>  
>  extern int vfio_platform_probe_common(struct vfio_platform_device *vdev,