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Date: Mon, 2 Dec 2019 07:42:48 -0300 From: Pablo Sebastián Greco <pgreco@...tosproject.org> To: Kalle Valo <kvalo@...eaurora.org> Cc: Felix Fietkau <nbd@....name>, Lorenzo Bianconi <lorenzo.bianconi83@...il.com>, Ryder Lee <ryder.lee@...iatek.com>, Roy Luo <royluo@...gle.com>, "David S. Miller" <davem@...emloft.net>, Matthias Brugger <matthias.bgg@...il.com>, linux-wireless@...r.kernel.org, netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v1] mt76: mt7615: Fix build with older compilers On 2/12/19 06:25, Kalle Valo wrote: > Pablo Greco <pgreco@...tosproject.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@...el.com> >> Signed-off-by: Pablo Greco <pgreco@...tosproject.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. Anything that doesn't check field at build time should work, but between losing a check, or turning an inline into a macro, I'd rather use the macro. > Or even better if we could fix FIELD_GET() to work with older compilers. > The problem is not FIELD_GET itself, is that the compiler is trying to use "field" as a variable, instead as the macro expansion of GENMASK, as if the function wasn't inline. In the linked page you can see this message BUILD_BUG_ON failed: (((field) + (1ULL << (__builtin_ffsll(field) - 1))) & (((field) + (1ULL << (__builtin_ffsll(field) - 1))) - 1)) != 0 _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) which is is not right, because "field" should never be used for that check. Pablo.
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