netdev - RE: [PATCH] qede: fix CONFIG_INFINIBAND

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Date:   Thu, 13 Oct 2016 09:34:41 +0000
From:   "Mintz, Yuval" <Yuval.Mintz@...ium.com>
To:     Arnd Bergmann <arnd@...db.de>
CC:     Ariel Elior <Ariel.Elior@...gic.com>,
        "everest-linux-l2@...gic.com" <everest-linux-l2@...gic.com>,
        Alexander Duyck <aduyck@...antis.com>,
        "Amrani, Ram" <Ram.Amrani@...ium.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>
Subject: RE: [PATCH] qede: fix CONFIG_INFINIBAND_QEDR=m build error


> > > -		if (cond)
> > > +		if (IS_ENABLED(CONFIG_INFINIBAND_QEDR) && cond)
> > >			qed_rdma_dpm_bar(p_hwfn, p_ptt);
> >
> > Why not simply fix the qed_roce.h empty implementation?
> 
> Mainly for consistency: we have a couple of interfaces that are called from the
> qed driver that are implemented in qed_roce.c. We can either use a 'static inline'
> helper for all of them, or use if(IS_ENABLED()) everywhere. Since this was the
> only function that had a helper and that helper was defined incorrectly, I went
> with the second option.

Actually, that's not the case. I think with this exception, all the rest of the prototypes
in qed_roce.h aren't really needed, as those functions should only be accessed via
the qed_rdma_ops. I'll remove those later [or we can remove them as part of v2].

The genereal qed* preference is to have empty static-inline implementations
in case content is compiled-out [Look at iov for example].

> > > -#if IS_ENABLED(CONFIG_INFINIBAND_QEDR)
> > > +	if (!IS_ENABLED(CONFIG_INFINIBAND_QEDR))
> > > +		return 0;
> > > +
> > >  	num_l2_queues = 0;
> > >  	for_each_hwfn(cdev, i)
> > >  		num_l2_queues += FEAT_NUM(&cdev->hwfns[i],
> QED_PF_L2_QUE); @@
> > > -738,7 +736,6 @@ static int qed_slowpath_setup_int(struct qed_dev
> > > *cdev,
> > >  	DP_VERBOSE(cdev, QED_MSG_RDMA, "roce_msix_cnt=%d
> > > roce_msix_base=%d\n",
> > >  		   cdev->int_params.rdma_msix_cnt,
> > >  		   cdev->int_params.rdma_msix_base); -#endif
> >
> > While I don't mind, you could have argued is that we're not removing
> > enough, not too much.
> > I.e., perhaps the rdma_msix_* fields should also have been ifdef-ed
> > instead. [in which case this solution would not have worked]
> 
> That would add even more #ifdefs though.

I agree. Although I'm never clear on the guidelines for the tradeoff - 
How much memory/code is considered too much so that you'd have
To ifdef code out instead of 'wasting'?
[I obviously don't claim 64 bytes of memory hit that threshold]
 
BTW, are you interested in doing a v2 for this? Or would you prefer
if we'd pick it up from here?

Thanks,
Yuval