From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bartlomiej Zolnierkiewicz Subject: Re: linux-next: build warning after merge of the fbdev tree Date: Tue, 2 Apr 2019 17:16:47 +0200 Message-ID: <14da80ce-4a9e-3571-2aca-98c90634ee29@samsung.com> References: <20190402093007.0b03b02e@canb.auug.org.au> <20190402123849.GA4562@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190402123849.GA4562@localhost.localdomain> Sender: linux-kernel-owner@vger.kernel.org To: Tom Li Cc: Sudip Mukherjee , Linux Next Mailing List , Linux Kernel Mailing List , "Gustavo A. R. Silva" , Kees Cook , linux-fbdev@vger.kernel.org List-Id: linux-next.vger.kernel.org On 04/02/2019 02:38 PM, Tom Li wrote: > On Tue, Apr 02, 2019 at 09:30:07AM +1100, Stephen Rothwell wrote: >> Hi Bartlomiej, >> >> After merging the fbdev tree, today's linux-next build (x86_64 >> allmodconfig) produced this warning: >> >> drivers/video/fbdev/sm712fb.c: In function 'smtc_blank': >> drivers/video/fbdev/sm712fb.c:900:4: warning: this statement may fall through [-Wimplicit-fallthrough=] >> smtc_seqw(0x6b, 0x02); >> ^~~~~~~~~~~~~~~~~~~~~ >> drivers/video/fbdev/sm712fb.c:901:3: note: here >> case 0x720: >> ^~~~ >> >> Introduced by commit >> >> f627caf55b8e ("fbdev: sm712fb: fix crashes and garbled display during DPMS modesetting") >> > > Nice catch! Thanks! > > This bug was introduced by me while attempting to fix another issue, a result of > my copy-paste error. Since it only reprograms the clock to a different frequency, > it's only a benign issue without visible side-effect, so it also evaded Sudip > Mukherjee's code review and regression tests. > > But what's I'm more concerned here is the failure of scripts/checkpatch.pl. I > thought ./checkpatch.pl should have caught it, but for some reasons it cannot > detect this one. > > $ ./scripts/checkpatch.pl 0001-fbdev-sm712fb-fix-crashes-and-garbled-display-during.patch > total: 0 errors, 0 warnings, 105 lines checked > > So I mistakenly assumed the patch doesn't have a problem... It seems checkpatch.pl > cannot detect fallthroughs in nested switch/case statements? I'm not sure. Should I > report it to the maintainers of checkpatch.pl? > > Anyway, please apply the following patch ASAP. > > Thanks, > Tom Li > >>>From 040fa4e6cc8b338cd845c11fd3efd7394ca55108 Mon Sep 17 00:00:00 2001 > From: Yifeng Li > Date: Tue, 2 Apr 2019 20:25:20 +0800 > Subject: [PATCH] fbdev: sm712fb: fix memory frequency by avoiding a > switch/case fallthrough. > > A fallthrough in switch/case was introduced in f627caf55b8e ("fbdev: > sm712fb: fix crashes and garbled display during DPMS modesetting"), > due to my copy-paste error, which would cause the memory clock frequency > for SM720 to be programmed to SM712. > > Since it only reprograms the clock to a different frequency, it's only > a benign issue without visible side-effect, so it also evaded Sudip > Mukherjee's code review and regression tests. scripts/checkpatch.pl > also failed to discover the issue, possibly due to nested switch > statements. > > This issue was found by Stephen Rothwell by building linux-next with > -Wimplicit-fallthrough. > > Reported-by: Stephen Rothwell > Fixes: f627caf55b8e ("fbdev: sm712fb: fix crashes and garbled display during DPMS modesetting") > Signed-off-by: Yifeng Li Applied to fbdev-for-next, thanks! > --- > drivers/video/fbdev/sm712fb.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/video/fbdev/sm712fb.c b/drivers/video/fbdev/sm712fb.c > index 1e2503b52c6f..f1dcc6766d1e 100644 > --- a/drivers/video/fbdev/sm712fb.c > +++ b/drivers/video/fbdev/sm712fb.c > @@ -898,6 +898,7 @@ static int smtc_blank(int blank_mode, struct fb_info *info) > case 0x712: > smtc_seqw(0x6a, 0x16); > smtc_seqw(0x6b, 0x02); > + break; > case 0x720: > smtc_seqw(0x6a, 0x0d); > smtc_seqw(0x6b, 0x02); Best regards, -- Bartlomiej Zolnierkiewicz Samsung R&D Institute Poland Samsung Electronics