[PATCH][next] Bluetooth: hci.h: Avoid a couple -Wflex-array-member-not-at-end warnings

[PATCH][next] Bluetooth: hci.h: Avoid a couple -Wflex-array-member-not-at-end warnings

[Gustavo A. R. Silva]

-Wflex-array-member-not-at-end was introduced in GCC-14, and we are
getting ready to enable it, globally.

struct hci_std_codecs and struct hci_std_codecs_v2 are flexible
structures, this is structures that contain a flexible-array member
(__u8 codec[]; and struct hci_std_codec_v2 codec[];, correspondingly.)

Since struct hci_rp_read_local_supported_codecs and struct
hci_rp_read_local_supported_codecs_v2 are defined by hardware, we
create the new struct hci_std_codecs_hdr and struct hci_std_codecs_v2_hdr
types, and use them to replace the object types causing trouble in
struct hci_rp_read_local_supported_codecs and struct
hci_rp_read_local_supported_codecs_v2, namely struct hci_std_codecs
std_codecs; and struct hci_std_codecs_v2_hdr std_codecs;.

Also, once -fms-extensions is enabled, we can use transparent struct
members in both struct hci_std_codecs and struct hci_std_codecs_v2_hdr.

Notice that the newly created types does not contain the flex-array
member `codec`, which is the object causing the -Wfamnae warnings.

After these changes, the size of struct hci_rp_read_local_supported_codecs
and struct hci_rp_read_local_supported_codecs_v2, along with their
member's offsets remain the same, hence the memory layouts don't
change:

Before changes:
struct hci_rp_read_local_supported_codecs {
        __u8                       status;               /*     0     1 */
        struct hci_std_codecs      std_codecs;           /*     1     1 */
        struct hci_vnd_codecs      vnd_codecs;           /*     2     1 */

        /* size: 3, cachelines: 1, members: 3 */
        /* last cacheline: 3 bytes */
} __attribute__((__packed__));

struct hci_rp_read_local_supported_codecs_v2 {
        __u8                       status;               /*     0     1 */
        struct hci_std_codecs_v2   std_codecs;           /*     1     1 */
        struct hci_vnd_codecs_v2   vendor_codecs;        /*     2     1 */

        /* size: 3, cachelines: 1, members: 3 */
        /* last cacheline: 3 bytes */
} __attribute__((__packed__));

After changes:
struct hci_rp_read_local_supported_codecs {
	__u8                       status;               /*     0     1 */
	struct hci_std_codecs_hdr  std_codecs;           /*     1     1 */
	struct hci_vnd_codecs      vnd_codecs;           /*     2     1 */

	/* size: 3, cachelines: 1, members: 3 */
	/* last cacheline: 3 bytes */
} __attribute__((__packed__));

struct hci_rp_read_local_supported_codecs_v2 {
	__u8                       status;               /*     0     1 */
	struct hci_std_codecs_v2_hdr std_codecs;         /*     1     1 */
	struct hci_vnd_codecs_v2   vendor_codecs;        /*     2     1 */

	/* size: 3, cachelines: 1, members: 3 */
	/* last cacheline: 3 bytes */
} __attribute__((__packed__));

With these changes fix the following warnings:

include/net/bluetooth/hci.h:1490:31: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
include/net/bluetooth/hci.h:1525:34: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 include/net/bluetooth/hci.h | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
index 89ad9470fa71..572b1c620c5d 100644
--- a/include/net/bluetooth/hci.h
+++ b/include/net/bluetooth/hci.h
@@ -1468,8 +1468,12 @@ struct hci_rp_read_data_block_size {
 } __packed;
 
 #define HCI_OP_READ_LOCAL_CODECS	0x100b
-struct hci_std_codecs {
+struct hci_std_codecs_hdr {
 	__u8	num;
+} __packed;
+
+struct hci_std_codecs {
+	struct hci_std_codecs_hdr;
 	__u8	codec[];
 } __packed;
 
@@ -1487,7 +1491,7 @@ struct hci_vnd_codecs {
 
 struct hci_rp_read_local_supported_codecs {
 	__u8	status;
-	struct hci_std_codecs std_codecs;
+	struct hci_std_codecs_hdr std_codecs;
 	struct hci_vnd_codecs vnd_codecs;
 } __packed;
 
@@ -1504,8 +1508,12 @@ struct hci_std_codec_v2 {
 	__u8	transport;
 } __packed;
 
-struct hci_std_codecs_v2 {
+struct hci_std_codecs_v2_hdr {
 	__u8	num;
+} __packed;
+
+struct hci_std_codecs_v2 {
+	struct hci_std_codecs_v2_hdr;
 	struct hci_std_codec_v2 codec[];
 } __packed;
 
@@ -1522,7 +1530,7 @@ struct hci_vnd_codecs_v2 {
 
 struct hci_rp_read_local_supported_codecs_v2 {
 	__u8	status;
-	struct hci_std_codecs_v2 std_codecs;
+	struct hci_std_codecs_v2_hdr std_codecs;
 	struct hci_vnd_codecs_v2 vendor_codecs;
 } __packed;
 
-- 
2.43.0