Re: [PATCH 05/14] isdn: isdnloop: suppress a gcc-7 warning

[Joe Perches <joe@perches.com>]

On Fri, 2017-07-14 at 11:25 +0200, Arnd Bergmann wrote:
> We test whether a bit is set in a mask here, which is correct
> but gcc warns about it as it thinks it might be confusing:
> 
> drivers/isdn/isdnloop/isdnloop.c:412:37: error: ?: using integer constants in boolean context, the expression will always evaluate to 'true' [-Werror=int-in-bool-context]
> 
> This replaces the negation of an integer with an equivalent
> comparison to zero, which gets rid of the warning.
[]
> diff --git a/drivers/isdn/isdnloop/isdnloop.c b/drivers/isdn/isdnloop/isdnloop.c
[]
> @@ -409,7 +409,7 @@ isdnloop_sendbuf(int channel, struct sk_buff *skb, isdnloop_card *card)
>  		return -EINVAL;
>  	}
>  	if (len) {
> -		if (!(card->flags & (channel) ? ISDNLOOP_FLAGS_B2ACTIVE : ISDNLOOP_FLAGS_B1ACTIVE))
> +		if ((card->flags & (channel) ? ISDNLOOP_FLAGS_B2ACTIVE : ISDNLOOP_FLAGS_B1ACTIVE) == 0)
>  			return 0;
>  		if (card->sndcount[channel] > ISDNLOOP_MAX_SQUEUE)
>  			return 0;

The if as written can not be zero.

drivers/isdn/isdnloop/isdnloop.h:#define ISDNLOOP_FLAGS_B1ACTIVE 1      /* B-Channel-1 is open           */
drivers/isdn/isdnloop/isdnloop.h:#define ISDNLOOP_FLAGS_B2ACTIVE 2      /* B-Channel-2 is open           */

Perhaps this is a logic defect and should be:

		if (!(card->flags & ((channel) ? ISDNLOOP_FLAGS_B2ACTIVE : ISDNLOOP_FLAGS_B1ACTIVE)))