Re: [PATCH][next] leds: Avoid -Wflex-array-member-not-at-end warning
From: Thomas Weißschuh
Date: Fri Mar 28 2025 - 14:31:51 EST
Hi Gustavo,
On 2025-03-28 08:33:22-0600, Gustavo A. R. Silva wrote:
> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
> getting ready to enable it, globally.
>
> Use the `DEFINE_RAW_FLEX()` helper for an on-stack definition of
> a flexible structure where the size of the flexible-array member
> is known at compile-time, and refactor the rest of the code,
> accordingly.
>
> So, with these changes, fix the following warning:
>
> drivers/leds/leds-cros_ec.c:70:40: 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@xxxxxxxxxx>
> ---
> drivers/leds/leds-cros_ec.c | 26 +++++++++++---------------
> 1 file changed, 11 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/leds/leds-cros_ec.c b/drivers/leds/leds-cros_ec.c
> index 275522b81ea5..6eab0474f52d 100644
> --- a/drivers/leds/leds-cros_ec.c
> +++ b/drivers/leds/leds-cros_ec.c
> @@ -66,24 +66,20 @@ static int cros_ec_led_send_cmd(struct cros_ec_device *cros_ec,
> union cros_ec_led_cmd_data *arg)
> {
> int ret;
> - struct {
> - struct cros_ec_command msg;
> - union cros_ec_led_cmd_data data;
> - } __packed buf = {
> - .msg = {
> - .version = 1,
> - .command = EC_CMD_LED_CONTROL,
> - .insize = sizeof(arg->resp),
> - .outsize = sizeof(arg->req),
> - },
> - .data.req = arg->req
> - };
> -
> - ret = cros_ec_cmd_xfer_status(cros_ec, &buf.msg);
> + DEFINE_RAW_FLEX(struct cros_ec_command, msg, data,
> + sizeof(union cros_ec_led_cmd_data));
> +
> + msg->version = 1;
> + msg->command = EC_CMD_LED_CONTROL;
> + msg->insize = sizeof(arg->resp);
> + msg->outsize = sizeof(arg->req);
> + *(struct ec_params_led_control *)msg->data = arg->req;
To be honest this looks really ugly and it's not at all obvious what is
going on. We have the utility function cros_ec_cmd() which would be the
nicer alternative. (Without having verified that it avoids the warning).
While it is slightly more expensive, I don't think it matters.
And if it does, the helper can be optimized.
(The same goes for my other cros_ec drivers)
> +
> + ret = cros_ec_cmd_xfer_status(cros_ec, msg);
> if (ret < 0)
> return ret;
>
> - arg->resp = buf.data.resp;
> + arg->resp = *(struct ec_response_led_control *)msg->data;
>
> return 0;
> }
Thomas