linux-kernel - RE: [PATCH] cw1200: fix bogus maybe-uninitialized warning

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Message-ID: <063D6719AE5E284EB5DD2968C1650D6DB0209E9A@AcuExch.aculab.com>
Date:   Tue, 25 Oct 2016 13:24:55 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Arnd Bergmann' <arnd@...db.de>,
        Solomon Peachy <pizza@...ftnet.org>,
        Kalle Valo <kvalo@...eaurora.org>
CC:     Johannes Berg <johannes.berg@...el.com>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] cw1200: fix bogus maybe-uninitialized warning

From: Of Arnd Bergmann
> Sent: 24 October 2016 16:42
 
> On x86, the cw1200 driver produces a rather silly warning about the
> possible use of the 'ret' variable without an initialization
> presumably after being confused by the architecture specific definition
> of WARN_ON:
> 
> drivers/net/wireless/st/cw1200/wsm.c: In function wsm_handle_rx:
> drivers/net/wireless/st/cw1200/wsm.c:1457:9: error: ret may be used uninitialized in this function [-
> Werror=maybe-uninitialized]
> 
> As the driver just checks the same variable twice here, we can simplify
> it by removing the second condition, which makes it more readable and
> avoids the warning.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/net/wireless/st/cw1200/wsm.c | 15 +++++++--------
>  1 file changed, 7 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/wireless/st/cw1200/wsm.c b/drivers/net/wireless/st/cw1200/wsm.c
> index 680d60eabc75..094e6637ade2 100644
> --- a/drivers/net/wireless/st/cw1200/wsm.c
> +++ b/drivers/net/wireless/st/cw1200/wsm.c
> @@ -385,14 +385,13 @@ static int wsm_multi_tx_confirm(struct cw1200_common *priv,
>  	if (WARN_ON(count <= 0))
>  		return -EINVAL;
> 
> -	if (count > 1) {
> -		/* We already released one buffer, now for the rest */
> -		ret = wsm_release_tx_buffer(priv, count - 1);
> -		if (ret < 0)
> -			return ret;
> -		else if (ret > 0)
> -			cw1200_bh_wakeup(priv);
> -	}
> +	/* We already released one buffer, now for the rest */
> +	ret = wsm_release_tx_buffer(priv, count - 1);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (ret > 0)
> +		cw1200_bh_wakeup(priv);

That doesn't look equivalent to me (when count == 1).

> 
>  	cw1200_debug_txed_multi(priv, count);
>  	for (i = 0; i < count; ++i) {

Convert this loop into a do ... while so the body executes at least once.

	David