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

Joe Perches
2016-08-14T12:07:11Z

On Sat, 2016-08-13 at 17:26 +0800, sunbing wrote:
> On Aug 12, 2016, at 22:30, Jes Sorensen <Jes.Sorensen@redhat.com> wrote:
> > sunbing <sunbing@redflag-linux.com> writes:
> > > On Aug 11, 2016, at 23:25, Jes Sorensen <Jes.Sorensen@redhat.com> wrote:
> > > > Bing Sun <sunbing@redflag-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: