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From: "Robert P. J. Day" <rpjday@crashcourse.ca>
To: Linux kernel netdev mailing list <netdev@vger.kernel.org>
Subject: any reason for "!!netif_carrier_ok" and "!!netif_dormant" in net-sysfs.c?
Date: Mon, 27 Aug 2018 04:55:29 -0400 (EDT)	[thread overview]
Message-ID: <alpine.LFD.2.21.1808270448030.28019@localhost.localdomain> (raw)


  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
========================================================================

             reply	other threads:[~2018-08-27 12:43 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-27  8:55 Robert P. J. Day [this message]
2018-08-27 16:04 ` any reason for "!!netif_carrier_ok" and "!!netif_dormant" in net-sysfs.c? David Miller
2018-08-27 16:16   ` rpjday
2018-08-27 16:45     ` Eric Dumazet
2018-08-27 16:50       ` rpjday
2018-08-27 16:54     ` Joe Perches

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