[PATCH] virtio_pci: fix capability format, comments

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

- queue size can actually be 0 which is not a power of 2
- fix capability format. PCI spec says:
	The layout of the information is vendor specific, except that the byte
	immediately following the “Next” pointer in the capability structure is
	defined to be a length field.
	This length field provides the number of bytes in the capability
	structure (including the ID and Next pointer bytes).

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

This patch is on top of the new layout branch, too

 include/uapi/linux/virtio_pci.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/virtio_pci.h b/include/uapi/linux/virtio_pci.h
index cda688f..a5ef8cd 100644
--- a/include/uapi/linux/virtio_pci.h
+++ b/include/uapi/linux/virtio_pci.h
@@ -129,6 +129,7 @@
 struct virtio_pci_cap {
 	__u8 cap_vndr;	/* Generic PCI field: PCI_CAP_ID_VNDR */
 	__u8 cap_next;	/* Generic PCI field: next ptr. */
+	__u8 cap_len;	/* Generic PCI field: capability length */
 	__u8 cfg_type;	/* One of the VIRTIO_PCI_CAP_*_CFG. */
 	__u8 bar;		/* Where to find it. */
 	__le32 offset;	/* Offset within bar. */
@@ -154,7 +155,7 @@ struct virtio_pci_common_cfg {
 
 	/* About a specific virtqueue. */
 	__le16 queue_select;		/* read-write */
-	__le16 queue_size;		/* read-write, power of 2. */
+	__le16 queue_size;		/* read-write, power of 2, or 0. */
 	__le16 queue_msix_vector;	/* read-write */
 	__le16 queue_enable;		/* read-write */
 	__le16 queue_notify_off;	/* read-only */
-- 
MST