netdev - Re: [PATCH net-next] amd-xgbe: Mark expected switch fall-throughs

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Date:   Thu, 25 Apr 2019 13:12:28 +0000
From:   "Lendacky, Thomas" <Thomas.Lendacky@....com>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        "David S. Miller" <davem@...emloft.net>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH net-next] amd-xgbe: Mark expected switch fall-throughs

On 4/24/19 11:08 AM, Gustavo A. R. Silva wrote:
> In preparation to enabling -Wimplicit-fallthrough, mark switch
> cases where we are expecting to fall through.
> 
> This patch fixes the following warnings:
> 
> In file included from drivers/net/ethernet/amd/xgbe/xgbe-drv.c:129:
> drivers/net/ethernet/amd/xgbe/xgbe-drv.c: In function ‘xgbe_set_hwtstamp_settings’:
> drivers/net/ethernet/amd/xgbe/xgbe-common.h:1392:9: warning: this statement may fall through [-Wimplicit-fallthrough=]
>   (_var) |= (((_val) & ((0x1 << (_width)) - 1)) << (_index)); \
>   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/net/ethernet/amd/xgbe/xgbe-common.h:1419:2: note: in expansion of macro ‘SET_BITS’
>   SET_BITS((_var),      \
>   ^~~~~~~~
> drivers/net/ethernet/amd/xgbe/xgbe-drv.c:1614:3: note: in expansion of macro ‘XGMAC_SET_BITS’
>    XGMAC_SET_BITS(mac_tscr, MAC_TSCR, TSVER2ENA, 1);
>    ^~~~~~~~~~~~~~
> drivers/net/ethernet/amd/xgbe/xgbe-drv.c:1616:2: note: here
>   case HWTSTAMP_FILTER_PTP_V1_L4_EVENT:
>   ^~~~
> In file included from drivers/net/ethernet/amd/xgbe/xgbe-drv.c:129:
> drivers/net/ethernet/amd/xgbe/xgbe-common.h:1392:9: warning: this statement may fall through [-Wimplicit-fallthrough=]
>   (_var) |= (((_val) & ((0x1 << (_width)) - 1)) << (_index)); \
>   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/net/ethernet/amd/xgbe/xgbe-common.h:1419:2: note: in expansion of macro ‘SET_BITS’
>   SET_BITS((_var),      \
>   ^~~~~~~~
> drivers/net/ethernet/amd/xgbe/xgbe-drv.c:1625:3: note: in expansion of macro ‘XGMAC_SET_BITS’
>    XGMAC_SET_BITS(mac_tscr, MAC_TSCR, TSVER2ENA, 1);
>    ^~~~~~~~~~~~~~
> drivers/net/ethernet/amd/xgbe/xgbe-drv.c:1627:2: note: here
>   case HWTSTAMP_FILTER_PTP_V1_L4_SYNC:
>   ^~~~
> In file included from drivers/net/ethernet/amd/xgbe/xgbe-drv.c:129:
> drivers/net/ethernet/amd/xgbe/xgbe-common.h:1392:9: warning: this statement may fall through [-Wimplicit-fallthrough=]
>   (_var) |= (((_val) & ((0x1 << (_width)) - 1)) << (_index)); \
>   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/net/ethernet/amd/xgbe/xgbe-common.h:1419:2: note: in expansion of macro ‘SET_BITS’
>   SET_BITS((_var),      \
>   ^~~~~~~~
> drivers/net/ethernet/amd/xgbe/xgbe-drv.c:1636:3: note: in expansion of macro ‘XGMAC_SET_BITS’
>    XGMAC_SET_BITS(mac_tscr, MAC_TSCR, TSVER2ENA, 1);
>    ^~~~~~~~~~~~~~
> drivers/net/ethernet/amd/xgbe/xgbe-drv.c:1638:2: note: here
>   case HWTSTAMP_FILTER_PTP_V1_L4_DELAY_REQ:
>   ^~~~
> 
> Warning level 3 was used: -Wimplicit-fallthrough=3
> 
> Notice that, in this particular case, the code comments are modified
> in accordance with what GCC is expecting to find.
> 
> This patch is part of the ongoing efforts to enable
> -Wimplicit-fallthrough.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> ---
>  drivers/net/ethernet/amd/xgbe/xgbe-drv.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-drv.c b/drivers/net/ethernet/amd/xgbe/xgbe-drv.c
> index 0cc911f928b1..3dd0cecddba8 100644
> --- a/drivers/net/ethernet/amd/xgbe/xgbe-drv.c
> +++ b/drivers/net/ethernet/amd/xgbe/xgbe-drv.c
> @@ -1612,7 +1612,7 @@ static int xgbe_set_hwtstamp_settings(struct xgbe_prv_data *pdata,
>  	/* PTP v2, UDP, any kind of event packet */
>  	case HWTSTAMP_FILTER_PTP_V2_L4_EVENT:
>  		XGMAC_SET_BITS(mac_tscr, MAC_TSCR, TSVER2ENA, 1);
> -	/* PTP v1, UDP, any kind of event packet */
> +		/* Fall through - to PTP v1, UDP, any kind of event packet */

If the compiler doesn't have a problem with adding just an indented
"Fall through" comment and leaving the original comment in place, I would
prefer that. It seems clearer to me.

Thanks,
Tom

>  	case HWTSTAMP_FILTER_PTP_V1_L4_EVENT:
>  		XGMAC_SET_BITS(mac_tscr, MAC_TSCR, TSIPV4ENA, 1);
>  		XGMAC_SET_BITS(mac_tscr, MAC_TSCR, TSIPV6ENA, 1);
> @@ -1623,7 +1623,7 @@ static int xgbe_set_hwtstamp_settings(struct xgbe_prv_data *pdata,
>  	/* PTP v2, UDP, Sync packet */
>  	case HWTSTAMP_FILTER_PTP_V2_L4_SYNC:
>  		XGMAC_SET_BITS(mac_tscr, MAC_TSCR, TSVER2ENA, 1);
> -	/* PTP v1, UDP, Sync packet */
> +		/* Fall through - to PTP v1, UDP, Sync packet */
>  	case HWTSTAMP_FILTER_PTP_V1_L4_SYNC:
>  		XGMAC_SET_BITS(mac_tscr, MAC_TSCR, TSIPV4ENA, 1);
>  		XGMAC_SET_BITS(mac_tscr, MAC_TSCR, TSIPV6ENA, 1);
> @@ -1634,7 +1634,7 @@ static int xgbe_set_hwtstamp_settings(struct xgbe_prv_data *pdata,
>  	/* PTP v2, UDP, Delay_req packet */
>  	case HWTSTAMP_FILTER_PTP_V2_L4_DELAY_REQ:
>  		XGMAC_SET_BITS(mac_tscr, MAC_TSCR, TSVER2ENA, 1);
> -	/* PTP v1, UDP, Delay_req packet */
> +		/* Fall through - to PTP v1, UDP, Delay_req packet */
>  	case HWTSTAMP_FILTER_PTP_V1_L4_DELAY_REQ:
>  		XGMAC_SET_BITS(mac_tscr, MAC_TSCR, TSIPV4ENA, 1);
>  		XGMAC_SET_BITS(mac_tscr, MAC_TSCR, TSIPV6ENA, 1);
>