linux-kernel - Re: [PATCH] Staging: rtl8723au: os_intfs: fixed case statement is variable issue

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Date:	Sun, 14 Aug 2016 05:07:03 -0700
From:	Joe Perches <joe@...ches.com>
To:	sunbing <sunbing@...flag-linux.com>,
	Jes Sorensen <Jes.Sorensen@...hat.com>
Cc:	Larry.Finger@...inger.net, gregkh@...uxfoundation.org,
	linux-wireless@...r.kernel.org, devel@...verdev.osuosl.org,
	linux-kernel@...r.kernel.org, sunbing.linux@...il.com,
	Johannes Berg <johannes@...solutions.net>
Subject: Re: [PATCH] Staging: rtl8723au: os_intfs: fixed case statement is
 variable issue

On Sat, 2016-08-13 at 17:26 +0800, sunbing wrote:
> On Aug 12, 2016, at 22:30, Jes Sorensen <Jes.Sorensen@...hat.com> wrote:
> > sunbing <sunbing@...flag-linux.com> writes:
> > > On Aug 11, 2016, at 23:25, Jes Sorensen <Jes.Sorensen@...hat.com> wrote:
> > > > Bing Sun <sunbing@...flag-linux.com> writes:
> > > > > 
> > > > > Fixed sparse parse error:
> > > > > Expected constant expression in case statement.
[]
> > > > Pardon me here, but I find it really hard to see how this change is an
> > > > improvement over the old code in any shape or form.
> > > There is no functional improvement. 
> > > But before this patch, when we do: make C=1 M=drivers/staging/rtl8723au/
> > > An error output: 
> > > drivers/staging/rtl8723au//os_dep/os_intfs.c:287:14: error: Expected
> > > constant expression in case statement
> > > To avoid sparse parse error, a case statement converts to an if statement.
> > > So we got this patch.
> > Hello
> > 
> > I understand this part, but it seems to me we are changing the code due
> > to a broken test case in sparse. Does the warning go away if you use
> > __constant_htons() instead of htons()?
> > 
> > Jes
> Thanks for your guidance.
> 
> 1. If I use __constant_htons, checkpatch.pl will warning:
>     WARNING: __constant_htons should be htons
> 
> 2. In os_intfs.c: rtw_classify8021d, there are only one case statement and a 
> default statement. So, convert "switch case" to "if else" is more readable in my opinion.
> 
> So, I pushed this patch.
> 
> There are some patches convert use of __constant_htons to htons in kernel logs. 
> Will there be a new patch convert to htons in the future if I use  __constant_htons now ?
> 
> After search through kernel code, there are 158 "case htons(...)" statements and 
> 2 "case __constant_htons(...)" statements. Does this mean we can ignore sparse 
> error and use "case htons(...)" ?
> 
> It makes me confused. More help, please.

It's a sparse defect.

Try again after patching sparse with Jes' patch:
http://marc.info/?l=linux-sparse&m=147091200720267&w=3