netdev - any reason for "!!netif_carrier_ok" and "!!netif

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Date:   Mon, 27 Aug 2018 04:55:29 -0400 (EDT)
From:   "Robert P. J. Day" <rpjday@...shcourse.ca>
To:     Linux kernel netdev mailing list <netdev@...r.kernel.org>
Subject: any reason for "!!netif_carrier_ok" and "!!netif_dormant" in
 net-sysfs.c?

  another pedantic oddity -- is there a reason for these two double
negations in net/core/net-sysfs.c?

static ssize_t carrier_show(struct device *dev,
                            struct device_attribute *attr, char *buf)
{
        struct net_device *netdev = to_net_dev(dev);

        if (netif_running(netdev))
                return sprintf(buf, fmt_dec, !!netif_carrier_ok(netdev));

...

static ssize_t dormant_show(struct device *dev,
                            struct device_attribute *attr, char *buf)
{
        struct net_device *netdev = to_net_dev(dev);

        if (netif_running(netdev))
                return sprintf(buf, fmt_dec, !!netif_dormant(netdev));

  i understand the normal rationale for !! in assuring a final boolean
value of precisely either 0 or 1 (here for the sake of printing), but
given that those two routines are declared with a return value of
"bool" in netdevice.h, i don't see any way that they can return
anything *other* than 0 or 1. i realize it can't possibly hurt, but
whenever i see this construct, i normally assume there's a *reason*
for it, but i can't see what it's doing in those two places.

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                  http://crashcourse.ca/dokuwiki

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
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