[PATCH v4 1/1] virtio_bt: Fix alignment in configuration struct

[Igor Skalkin]

The current version of the configuration structure has unaligned
16-bit fields, but according to the specification [1], access to
the configuration space must be aligned.

Add a second, aligned  version of the configuration structure
and a new feature bit indicating that this version is being used.

[1] https://docs.oasis-open.org/virtio/virtio/v1.1/virtio-v1.1.pdf

Signed-off-by: Igor Skalkin <Igor.Skalkin@xxxxxxxxxxxxxxx>
---
 drivers/bluetooth/virtio_bt.c  | 16 +++++++++++++---
 include/uapi/linux/virtio_bt.h |  8 ++++++++
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/drivers/bluetooth/virtio_bt.c b/drivers/bluetooth/virtio_bt.c
index 67c21263f9e0..35f8041722c8 100644
--- a/drivers/bluetooth/virtio_bt.c
+++ b/drivers/bluetooth/virtio_bt.c
@@ -306,7 +306,12 @@ static int virtbt_probe(struct virtio_device *vdev)
 	if (virtio_has_feature(vdev, VIRTIO_BT_F_VND_HCI)) {
 		__u16 vendor;
 
-		virtio_cread(vdev, struct virtio_bt_config, vendor, &vendor);
+		if (virtio_has_feature(vdev, VIRTIO_BT_F_CONFIG_V2))
+			virtio_cread(vdev, struct virtio_bt_config_v2,
+				     vendor, &vendor);
+		else
+			virtio_cread(vdev, struct virtio_bt_config,
+				     vendor, &vendor);
 
 		switch (vendor) {
 		case VIRTIO_BT_CONFIG_VENDOR_ZEPHYR:
@@ -339,8 +344,12 @@ static int virtbt_probe(struct virtio_device *vdev)
 	if (virtio_has_feature(vdev, VIRTIO_BT_F_MSFT_EXT)) {
 		__u16 msft_opcode;
 
-		virtio_cread(vdev, struct virtio_bt_config,
-			     msft_opcode, &msft_opcode);
+		if (virtio_has_feature(vdev, VIRTIO_BT_F_CONFIG_V2))
+			virtio_cread(vdev, struct virtio_bt_config_v2,
+				     msft_opcode, &msft_opcode);
+		else
+			virtio_cread(vdev, struct virtio_bt_config,
+				     msft_opcode, &msft_opcode);
 
 		hci_set_msft_opcode(hdev, msft_opcode);
 	}
@@ -387,6 +396,7 @@ static const unsigned int virtbt_features[] = {
 	VIRTIO_BT_F_VND_HCI,
 	VIRTIO_BT_F_MSFT_EXT,
 	VIRTIO_BT_F_AOSP_EXT,
+	VIRTIO_BT_F_CONFIG_V2,
 };
 
 static struct virtio_driver virtbt_driver = {
diff --git a/include/uapi/linux/virtio_bt.h b/include/uapi/linux/virtio_bt.h
index a7bd48daa9a9..af798f4c9680 100644
--- a/include/uapi/linux/virtio_bt.h
+++ b/include/uapi/linux/virtio_bt.h
@@ -9,6 +9,7 @@
 #define VIRTIO_BT_F_VND_HCI	0	/* Indicates vendor command support */
 #define VIRTIO_BT_F_MSFT_EXT	1	/* Indicates MSFT vendor support */
 #define VIRTIO_BT_F_AOSP_EXT	2	/* Indicates AOSP vendor support */
+#define VIRTIO_BT_F_CONFIG_V2	3	/* Use second version configuration */
 
 enum virtio_bt_config_type {
 	VIRTIO_BT_CONFIG_TYPE_PRIMARY	= 0,
@@ -28,4 +29,11 @@ struct virtio_bt_config {
 	__u16 msft_opcode;
 } __attribute__((packed));
 
+struct virtio_bt_config_v2 {
+	__u8  type;
+	__u8  alignment;
+	__u16 vendor;
+	__u16 msft_opcode;
+};
+
 #endif /* _UAPI_LINUX_VIRTIO_BT_H */
-- 
2.37.2