wifi: iwlegacy: Avoid multiple -Wflex-array-member-not-at-end warnings

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

So, in order to avoid ending up with a flexible-array member in the
middle of multiple other structs, we use the `__struct_group()`
helper to create new tagged structures with the suffix `_hdr`.
These structures group together all the members of the original
flexible structures except the flexible arrays.

As a result, the arrays are effectively separated from the rest of the
members without modifying the memory layout of the flexible structures.
We then change the type of the middle struct members currently causing
trouble from the original flex struct to the newly created structs with
suffix `_hdr`.

We also want to ensure that when new members need to be added to the
flexible structures, they are always included within the newly created
tagged structs. For this, we use `static_assert()`. This ensures that the
memory layout for both the flexible structure and the new tagged struct
is the same after any changes.

This approach avoids having to implement the `_hdr` structures as
completely separate structures, thus preventing having to maintain
two independent but basically identical structures, closing the door
to potential bugs in the future.

We also use `container_of()` whenever we need to retrieve a pointer to
the flexible structure, through which we can access the flexible-array
member, if necessary.

Also, remove a couple of unused zero-length arrays and flexible-array
members.

So, with these changes, fix the following warnings:

drivers/net/wireless/intel/iwlegacy/commands.h:1196:38: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/wireless/intel/iwlegacy/commands.h:1197:36: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/wireless/intel/iwlegacy/commands.h:2505:30: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/wireless/intel/iwlegacy/commands.h:2549:26: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/wireless/intel/iwlegacy/commands.h:2654:31: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/wireless/intel/iwlegacy/commands.h:2665:30: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/wireless/intel/iwlegacy/commands.h:2673:26: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/net/wireless/intel/iwlegacy/commands.h:3349:30: 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>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://patch.msgid.link/Zr2gxERA3RL3EwRe@elsanto

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/net/wireless/intel/iwlegacy/3945.c b/drivers/net/wireless/intel/iwlegacy/3945.c
index 1fab7849f56d..e95800b77f6b 100644
--- a/drivers/net/wireless/intel/iwlegacy/3945.c
+++ b/drivers/net/wireless/intel/iwlegacy/3945.c
@@ -527,7 +527,7 @@ il3945_hdl_rx(struct il_priv *il, struct il_rx_buf *rxb)
 	struct ieee80211_hdr *header;
 	struct ieee80211_rx_status rx_status = {};
 	struct il_rx_pkt *pkt = rxb_addr(rxb);
-	struct il3945_rx_frame_stats *rx_stats = IL_RX_STATS(pkt);
+	struct il3945_rx_frame_stats_hdr *rx_stats = IL_RX_STATS(pkt);
 	struct il3945_rx_frame_hdr *rx_hdr = IL_RX_HDR(pkt);
 	struct il3945_rx_frame_end *rx_end = IL_RX_END(pkt);
 	u16 rx_stats_sig_avg __maybe_unused = le16_to_cpu(rx_stats->sig_avg);