linux-kernel - Re: [Intel-gfx] [PATCH] drm/i915: mark expected switch fall-through

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Message-ID: <26740470-d7b7-0a58-0aae-fc628bd4f416@embeddedor.com>
Date:   Wed, 20 Jun 2018 16:27:05 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Rodrigo Vivi <rodrigo.vivi@...el.com>
Cc:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        David Airlie <airlied@...ux.ie>,
        intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH] drm/i915: mark expected switch fall-through

On 06/20/2018 02:06 PM, Rodrigo Vivi wrote:
> On Wed, Jun 20, 2018 at 08:31:00AM -0500, Gustavo A. R. Silva wrote:
>> In preparation to enabling -Wimplicit-fallthrough, mark switch cases
>> where we are expecting to fall through.
>>
>> Addresses-Coverity-ID: 1470102 ("Missing break in switch")
> 
> Any other advantage besides coverity?
> Can't we address it by marking as "Intentional" on the tool?
> 

Yes. The advantage of this is that it will eventually allows to enable 
-Wimplicit-fallthrough, hence, enabling the compiler to trigger a 
warning, which will force us to double check if we are actually missing 
a break before committing the code.

The change in the code has nothing to do with the Coverity tool. The 
tool is only reporting the issue, which, in this case, is a false positive.

> I'm afraid there will be so many more places to add fallthrough
> marks....
> 

Oh yeah, there are around 1000 similar places in the whole codebase. 
There is an ongoing effort to review each case. Months ago, it used to 
be around 1500 of these cases.

Thanks
--
Gustavo

>> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
>> ---
>>   drivers/gpu/drm/i915/intel_dpll_mgr.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_dpll_mgr.c b/drivers/gpu/drm/i915/intel_dpll_mgr.c
>> index 132fe63..6a40a77 100644
>> --- a/drivers/gpu/drm/i915/intel_dpll_mgr.c
>> +++ b/drivers/gpu/drm/i915/intel_dpll_mgr.c
>> @@ -2566,6 +2566,7 @@ int icl_calc_dp_combo_pll_link(struct drm_i915_private *dev_priv,
>>   	switch (index) {
>>   	default:
>>   		MISSING_CASE(index);
>> +		/* fall through */
>>   	case 0:
>>   		link_clock = 540000;
>>   		break;
>> -- 
>> 2.7.4
>>
>> _______________________________________________
>> Intel-gfx mailing list
>> Intel-gfx@...ts.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

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