Hi Bernard. On Fri, Oct 23, 2020 at 03:48:49PM +0800, Bernard wrote: > > > From: Thomas Zimmermann <tzimmerm...@suse.de> > Date: 2020-10-23 15:13:30 > To: Bernard Zhao <bern...@vivo.com>,Dave Airlie <airl...@redhat.com>,David > Airlie <airl...@linux.ie>,Daniel Vetter > <dan...@ffwll.ch>,dri-de...@lists.freedesktop.org,linux-kernel@vger.kernel.org > Cc: opensource.ker...@vivo.com > Subject: Re: [PATCH] gpu/drm/mgag200:remove break after return>Hi > > > >On 23.10.20 09:00, Bernard Zhao wrote: > >> In function mgag200_set_pci_regs, there are some switch cases > >> returned, then break. These break will never run. > >> This patch is to make the code a bit readable. > >> > >> Signed-off-by: Bernard Zhao <bern...@vivo.com> > >> --- > >> drivers/gpu/drm/mgag200/mgag200_mode.c | 5 +---- > >> 1 file changed, 1 insertion(+), 4 deletions(-) > >> > >> diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c > >> b/drivers/gpu/drm/mgag200/mgag200_mode.c > >> index 38672f9e5c4f..de873a5d276e 100644 > >> --- a/drivers/gpu/drm/mgag200/mgag200_mode.c > >> +++ b/drivers/gpu/drm/mgag200/mgag200_mode.c > >> @@ -794,20 +794,17 @@ static int mgag200_crtc_set_plls(struct mga_device > >> *mdev, long clock) > >> case G200_SE_A: > >> case G200_SE_B: > >> return mga_g200se_set_plls(mdev, clock); > >> - break; > >> case G200_WB: > >> case G200_EW3: > >> return mga_g200wb_set_plls(mdev, clock); > >> - break; > >> case G200_EV: > >> return mga_g200ev_set_plls(mdev, clock); > >> - break; > >> case G200_EH: > >> case G200_EH3: > >> return mga_g200eh_set_plls(mdev, clock); > >> - break; > >> case G200_ER: > >> return mga_g200er_set_plls(mdev, clock); > >> + default: > > > >No default case here. If one of the enum values is not handled by the > >switch, the compiler should warn about it. > > Hi > > For this point I was a little confused, about this switch variable > "mdev->type", my understanding is that this variable`s value can be certain > only when the code is running. > How does the compiler warn this("If one of the enum values is not handled") > before the code runs?
If the switch/case does not include "G200_ER" then the compiler can see one enum value is missing from the list and can warn. As a test - Try to drop the default and drop G200_ER - then the compiler (hopefully) will warn. Sam