linux-kernel - Re: [PATCH][next] platform/chrome: cros_ec: Avoid -Wflex-array-member-not-at-end warning

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Message-ID: <Z-u9TNrnEGD8fM8V@google.com>
Date: Tue, 1 Apr 2025 10:17:48 +0000
From: Tzung-Bi Shih <tzungbi@...nel.org>
To: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Benson Leung <bleung@...omium.org>, Guenter Roeck <groeck@...omium.org>,
	chrome-platform@...ts.linux.dev, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] platform/chrome: cros_ec: Avoid
 -Wflex-array-member-not-at-end warning

On Fri, Mar 28, 2025 at 07:50:11AM -0600, Gustavo A. R. Silva wrote:
> +union cros_ec_sleep_data {
> +	struct ec_params_host_sleep_event req0;
> +	struct ec_params_host_sleep_event_v1 req1;
> +	struct ec_response_host_sleep_event_v1 resp1;
> +} __packed;

The __packed modifier seems redundant.

>  static int cros_ec_sleep_event(struct cros_ec_device *ec_dev, u8 sleep_event)
>  {
>  	int ret;
> -	struct {
> -		struct cros_ec_command msg;
> -		union {
> -			struct ec_params_host_sleep_event req0;
> -			struct ec_params_host_sleep_event_v1 req1;
> -			struct ec_response_host_sleep_event_v1 resp1;
> -		} u;
> -	} __packed buf;
> +	DEFINE_RAW_FLEX(struct cros_ec_command, msg, data,
> +			sizeof(union cros_ec_sleep_data));

Is it possible to use something similar to:

MAX(MAX(sizeof(A), sizeof(B)),
    sizeof(C))

so that the union doesn't need to be defined?