Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | Date | Tue, 2 Apr 2019 20:38:50 +0800 | From | Tom Li <> | Subject | Re: linux-next: build warning after merge of the fbdev tree |
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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 <tomli@tomli.me> 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 <sfr@canb.auug.org.au> Fixes: f627caf55b8e ("fbdev: sm712fb: fix crashes and garbled display during DPMS modesetting") Signed-off-by: Yifeng Li <tomli@tomli.me> --- 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); -- 2.20.1
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