From: Sam Ravnborg <s...@ravnborg.org>
Date: 2020-10-25 01:14:57
To: Bernard <bern...@vivo.com>
Cc: Thomas Zimmermann <tzimmerm...@suse.de>,opensource.ker...@vivo.com,David
Airlie
<airl...@linux.ie>,linux-ker...@vger.kernel.org,dri-devel@lists.freedesktop.org,Dave
Airlie <airl...@redhat.com>
Subject: Re: Re: [PATCH] gpu/drm/mgag200:remove break after return>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-devel@lists.freedesktop.org,linux-ker...@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.
Hi, Sam & Thomas：
Thank you very much for your kind comments, I learned new useful knowledge.
I will resubmit the patch.
BR//Bernard
> Sam
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