[PATCH][next] wifi: mwl8k: Use static_assert() to check struct sizes

From: Gustavo A. R. Silva
Date: Thu Aug 08 2024 - 18:11:30 EST


Commit 5c4250092fad ("wifi: mwl8k: Avoid -Wflex-array-member-not-at-end
warnings") introduced tagged `struct mwl8k_cmd_pkt_hdr`. We want to
ensure that when new members need to be added to the flexible structure,
they are always included within this tagged struct.

We use `static_assert()` to ensure that the memory layout for both
the flexible structure and the tagged struct is the same after any
changes.

Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
---
drivers/net/wireless/marvell/mwl8k.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/net/wireless/marvell/mwl8k.c b/drivers/net/wireless/marvell/mwl8k.c
index b130e057370f..bab9ef37a1ab 100644
--- a/drivers/net/wireless/marvell/mwl8k.c
+++ b/drivers/net/wireless/marvell/mwl8k.c
@@ -587,6 +587,7 @@ static int mwl8k_request_firmware(struct mwl8k_priv *priv, char *fw_image,
}

struct mwl8k_cmd_pkt {
+ /* New members MUST be added within the __struct_group() macro below. */
__struct_group(mwl8k_cmd_pkt_hdr, hdr, __packed,
__le16 code;
__le16 length;
@@ -596,6 +597,8 @@ struct mwl8k_cmd_pkt {
);
char payload[];
} __packed;
+static_assert(offsetof(struct mwl8k_cmd_pkt, payload) == sizeof(struct mwl8k_cmd_pkt_hdr),
+ "struct member likely outside of __struct_group()");

/*
* Firmware loading.
--
2.34.1