[PATCHv2] virtio_pci: better macro exported in uapi

["Michael S. Tsirkin" <mst@redhat.com>]

Macro VIRTIO_PCI_CONFIG assumes that userspace actually has a structure
with a field named msix_enabled.  Add VIRTIO_PCI_CONFIG_OFF that gets
the msix_enabled by value instead, to make it useful for userspace.  We
still keep VIRTIO_PCI_CONFIG around for now, in case some userspace uses
it.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---

Changes from v1:
- rename macro to VIRTIO_PCI_CONFIG_OFF so preprocessor
  can be used to check for its presence, as suggested
  by Rusty
- keep old macro around as suggested by David Howells

 include/uapi/linux/virtio_pci.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/virtio_pci.h b/include/uapi/linux/virtio_pci.h
index ea66f3f..e5ec1ca 100644
--- a/include/uapi/linux/virtio_pci.h
+++ b/include/uapi/linux/virtio_pci.h
@@ -80,7 +80,9 @@
 
 /* The remaining space is defined by each driver as the per-driver
  * configuration space */
-#define VIRTIO_PCI_CONFIG(dev)		((dev)->msix_enabled ? 24 : 20)
+#define VIRTIO_PCI_CONFIG_OFF(msix_enabled)	((msix_enabled) ? 24 : 20)
+/* Deprecated: please use VIRTIO_PCI_CONFIG_OFF instead */
+#define VIRTIO_PCI_CONFIG(dev)	VIRTIO_PCI_CONFIG_OFF((dev)->msix_enabled)
 
 /* Virtio ABI version, this must match exactly */
 #define VIRTIO_PCI_ABI_VERSION		0
-- 
MST