linux-kernel - Re: [RFC] wifi: iwlwifi: mei: Remove unused flexible-array member in struct iwl_sap

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Message-ID: <ed9e34c4-ab63-47cd-b27a-9aa18cd91180@embeddedor.com>
Date: Wed, 27 Aug 2025 10:20:34 +0200
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Johannes Berg <johannes@...solutions.net>,
 Miri Korenblit <miriam.rachel.korenblit@...el.com>
Cc: linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC] wifi: iwlwifi: mei: Remove unused flexible-array member in
 struct iwl_sap_hdr?

On 25/08/25 10:20, Johannes Berg wrote:
> On Mon, 2025-08-11 at 17:23 +0900, Gustavo A. R. Silva wrote:
>> Hi all,
>>
>> At first sight, it seems that the flexible-array member `payload`
>> in the struct below it's not being used:
>>
>> drivers/net/wireless/intel/iwlwifi/mei/sap.h:
>> 298 /**
>> 299  * struct iwl_sap_hdr - prefixes any SAP message
>> 300  * @type: See &enum iwl_sap_msg.
>> 301  * @len: The length of the message (header not included).
>> 302  * @seq_num: For debug.
>> 303  * @payload: The payload of the message.
>> 304  */
>> 305 struct iwl_sap_hdr {
>> 306         __le16 type;
>> 307         __le16 len;
>> 308         __le32 seq_num;
>> 309         u8 payload[];
>> 310 };
>>
>> If we remove it, we'd get rid of 14 of the following type of warnings:
>>
>> drivers/net/wireless/intel/iwlwifi/mei/sap.h:318:28: warning: structure containing a flexible array member is not at the end of another structure
>> [-Wflex-array-member-not-at-end]
>>
>> Is there any case where this array is actually used that I might
>> be missing?
> 
> Check if it builds? But I don't see it used in our internal (and
> possibly more recent) version of this either.

It seems that the whole thing is actually broken, see commit 8997f5c8a627
("wifi: iwlwifi: Mark IWLMEI as broken").

However, nothing complains when built without that array. So, I've just
submitted a patch.

Thanks!
-Gustavo