linux-kernel - Re: [PATCH] staging: vt6656: Use fls instead of for loop in vnt_update_top

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 20 Apr 2020 15:10:59 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Oscar Carter <oscar.carter@....com>
Cc:     Forest Bond <forest@...ttletooquiet.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        devel@...verdev.osuosl.org, Malcolm Priestley <tvboxspy@...il.com>,
        "John B . Wyatt IV" <jbwyatt4@...il.com>,
        linux-kernel@...r.kernel.org,
        Colin Ian King <colin.king@...onical.com>
Subject: Re: [PATCH] staging: vt6656: Use fls instead of for loop in
 vnt_update_top_rates

On Sun, Apr 19, 2020 at 12:09:21PM +0200, Oscar Carter wrote:
> -	for (i = RATE_11M;; i--) {
> -		if (priv->basic_rates & (u16)(1 << i)) {
> -			top_cck = i;
> -			break;
> -		}
> -		if (i == RATE_1M)
> -			break;
> -	}
> +	pos = fls(priv->basic_rates & GENMASK(RATE_54M, RATE_6M));
> +	priv->top_ofdm_basic_rate = pos ? pos-- : RATE_24M;
                                          ^^^^^
Argh...  Come on.  I don't want to have to break out the C standard to
see if this is defined behavior and where the sequence points are.  A
pre-op would be clear but the most clear thing is to write it like this:

	priv->top_ofdm_basic_rate = pos ? (pos - 1) : RATE_24M;


> 
> -	priv->top_cck_basic_rate = top_cck;
> +	pos = fls(priv->basic_rates & GENMASK(RATE_11M, RATE_1M));
> +	priv->top_cck_basic_rate = pos ? pos-- : RATE_1M;
                                         ^^^^^
Same.

regards,
dan carpenter