On Fri, Jul 14, 2017 at 12:37:05PM +0200, Arnd Bergmann wrote:

On Fri, Jul 14, 2017 at 12:08 PM, Joe Perches [off-list ref] wrote:

quoted

On Fri, 2017-07-14 at 11:25 +0200, Arnd Bergmann wrote:

quoted

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]

...

quoted

Perhaps this is a logic defect and should be:

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

Yes, good catch. I had thought about it for a bit whether that would be
the answer, but come to the wrong conclusion on my own.

Note that the version you suggested will still have the warning, so I think
it needs to be

It shouldn't - the warning is for using an integer *constant* in boolean
context, but the result of & isn't a constant and should be fine.

!(flags & mask) is a very common idiom.

    - Kevin