linux-kernel - Re: [RESEND PATCH] staging: rtl8188eu: Fix else after return WARNING (checkpatch)

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Date:   Mon, 14 Sep 2020 09:42:49 -0700
From:   Joe Perches <joe@...ches.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Sohom Datta <sohom.datta@...rner.manipal.edu>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        Larry Finger <Larry.Finger@...inger.net>
Subject: Re: [RESEND PATCH] staging: rtl8188eu: Fix else after return
 WARNING (checkpatch)

On Mon, 2020-09-14 at 17:57 +0300, Dan Carpenter wrote:
> On Sun, Sep 13, 2020 at 12:19:50PM +0530, Sohom Datta wrote:
> > > From 4c8c8f3ff7f4d711daea4ac3bb987fcecc7ef1ed Mon Sep 17 00:00:00 2001
> > From: Sohom <sohom.datta@...rner.manipal.edu>
> > Date: Sat, 12 Sep 2020 18:04:56 +0530
> > Subject: [RESEND PATCH] staging: rtl8188eu: Fix else after return WARNING
> >  (checkpatch)
> > 
> > Fixed:
> > WARNING: else is not generally useful after a break or return
> > 1636: FILE: ./rtw_recv.c:1636:
> > +           return false;
> > +       else
> > 
> > Separated the return statement into a separate block since
> > it doesn't seem to depend on the SN_LESS explicity being false.
> > 
> > Signed-off-by: Sohom <sohom.datta@...rner.manipal.edu>
> > ---
> >  drivers/staging/rtl8188eu/core/rtw_recv.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/staging/rtl8188eu/core/rtw_recv.c b/drivers/staging/rtl8188eu/core/rtw_recv.c
> > index 5fe7a0458dd2..5e81134ffb6d 100644
> > --- a/drivers/staging/rtl8188eu/core/rtw_recv.c
> > +++ b/drivers/staging/rtl8188eu/core/rtw_recv.c
> > @@ -1629,10 +1629,11 @@ static int enqueue_reorder_recvframe(struct recv_reorder_ctrl *preorder_ctrl,
> >  		hdr = list_entry(plist, struct recv_frame, list);
> >  		pnextattrib = &hdr->attrib;
> >  
> > +		if (SN_EQUAL(pnextattrib->seq_num, pattrib->seq_num))
> > +			return false;
> > +
> >  		if (SN_LESS(pnextattrib->seq_num, pattrib->seq_num))
> >  			plist = plist->next;
> > -		else if (SN_EQUAL(pnextattrib->seq_num, pattrib->seq_num))
> > -			return false;
> >  		else
> >  			break;
> >  	}
> 
> Checkpatch is just wrong here.  Ignore it when it's wrong.

It's not "wrong" here.  It's making a suggestion.

Perhaps read the SN_EQUAL and SN_LESS macros.

a and b are both u16's here.

drivers/staging/rtl8188eu/include/rtw_recv.h:#define SN_LESS(a, b)              (((a - b) & 0x800) != 0)
drivers/staging/rtl8188eu/include/rtw_recv.h:#define SN_EQUAL(a, b)     (a == b)

Reordering works, perhaps it's just a question of
whether it's the most likely result of the test.

This is in a while loop.

If the expected test is really the most likely that
SN_LESS is true, then perhaps this loop could be
something like:

		if (SN_LESS(pnextattrib->seq_num, pattrib->seq_num)) {
			plist = plist->next;
			continue;
		}
		if (SN_EQUAL(pnextattrib->seq_num, pattrib->seq_num))
			return false;
		break;
	}

The real question is whether or not that's more readable.