netdev - Re: [PATCH] vmxnet3: fix LRO feature check

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Message-ID: <20180320182430.GA65@silver-peak.com>
Date:   Tue, 20 Mar 2018 11:24:32 -0700
From:   Igor Pylypiv <ipylypiv@...ver-peak.com>
To:     David Miller <davem@...emloft.net>
Cc:     lkp@...el.com, kbuild-all@...org, skhare@...are.com,
        pv-drivers@...are.com, netdev@...r.kernel.org
Subject: Re: [PATCH] vmxnet3: fix LRO feature check

The 03/20/2018 10:57, David Miller wrote:
> From: kbuild test robot <lkp@...el.com>
> Date: Sun, 18 Mar 2018 14:37:35 +0800
> 
> > All warnings (new ones prefixed by >>):
> > 
> >    drivers/net/vmxnet3/vmxnet3_drv.c: In function 'vmxnet3_rq_rx_complete':
> >>> drivers/net/vmxnet3/vmxnet3_drv.c:1474:8: warning: suggest parentheses around operand of '!' or change '&' to '&&' or '!' to '~' [-Wparentheses]
> >            !adapter->netdev->features & NETIF_F_LRO) {
> >            ^~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Igor, I will fix this up for you.  But it is clear that this patch wasn't tested
> very well.
> 
> Because !adapter->netdev->features evaluates wholly before the "& NETIF_F_LRO",
> the flags aren't being tested properly at all.

My bad.

I have even been looking at C operator precedence table:

----------------------------
| Operator | Associativity |
|--------------------------|
| ++ --    | right-to-left |
| + -      |               |
| ! ~      |               |
| (type)   |               |
| *        |               |
| &        |               |
| sizeof   |               |
----------------------------

According to this table '&' will be evaluated first, because it is on the right side.

But yeah, that was "Address of", not "Bitwise AND".