Re: [PATCH v1] mt76: mt7615: Fix build with older compilers

From: Kalle Valo <kvalo@codeaurora.org>
To: Pablo Greco <pgreco@centosproject.org>
Cc: Ryder Lee <ryder.lee@mediatek.com>,
	netdev@vger.kernel.org, linux-wireless@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Matthias Brugger <matthias.bgg@gmail.com>,
	linux-mediatek@lists.infradead.org, Roy Luo <royluo@google.com>,
	Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	linux-arm-kernel@lists.infradead.org,
	Felix Fietkau <nbd@nbd.name>
Subject: Re: [PATCH v1] mt76: mt7615: Fix build with older compilers
Date: Mon, 2 Dec 2019 09:25:05 +0000	[thread overview]
Message-ID: <0101016ec5ed7c1c-0d86f585-372a-4b20-af6e-5b59e732b70c-000000@us-west-2.amazonses.com> (raw)
In-Reply-To: <20191201181716.61892-1-pgreco@centosproject.org> (Pablo Greco's message of "Sun, 1 Dec 2019 15:17:10 -0300")

Pablo Greco <pgreco@centosproject.org> writes:

> Some compilers (tested with 4.8.5 from CentOS 7) fail properly process
> FIELD_GET inside an inline function, which ends up in a BUILD_BUG_ON.
> Convert inline function to a macro.
>
> Fixes commit bf92e7685100 ("mt76: mt7615: add support for per-chain
> signal strength reporting")
> Reported in https://lkml.org/lkml/2019/9/21/146
>
> Reported-by: kbuild test robot <lkp@intel.com>
> Signed-off-by: Pablo Greco <pgreco@centosproject.org>
> ---
>  drivers/net/wireless/mediatek/mt76/mt7615/mac.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/drivers/net/wireless/mediatek/mt76/mt7615/mac.c b/drivers/net/wireless/mediatek/mt76/mt7615/mac.c
> index c77adc5d2552..77e395ca2c6a 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt7615/mac.c
> +++ b/drivers/net/wireless/mediatek/mt76/mt7615/mac.c
> @@ -13,10 +13,7 @@
>  #include "../dma.h"
>  #include "mac.h"
>  
> -static inline s8 to_rssi(u32 field, u32 rxv)
> -{
> -	return (FIELD_GET(field, rxv) - 220) / 2;
> -}
> +#define to_rssi(field, rxv)		((FIELD_GET(field, rxv) - 220) / 2)

What about u32_get_bits() instead of FIELD_GET(), would that work? I
guess chances for that is slim, but it's always a shame to convert a
function to a macro so we should try other methods first.

Or even better if we could fix FIELD_GET() to work with older compilers.

-- 
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches

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