linux-kernel - Re: [PATCH net-next v7 5/6] stmmac: dwmac-mediatek: add support for mt8195

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Date:   Thu, 9 Dec 2021 09:42:08 +0800
From:   Biao Huang <biao.huang@...iatek.com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     <davem@...emloft.net>, Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        <netdev@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <srv_heupstream@...iatek.com>, <macpaul.lin@...iatek.com>,
        <angelogioacchino.delregno@...labora.com>, <dkirjanov@...e.de>
Subject: Re: [PATCH net-next v7 5/6] stmmac: dwmac-mediatek: add support for
 mt8195

Dear Jakub,

All these warning lines share a similar semantics:
delay_val |= FIELD_PREP(xxx, !!val);

and, should come from the expansion of FIELD_PREP in
include/linux/bitfiled.h:

  FIELD _PREP --> __BF_FILED_CHECK --> "~((_mask) >> __bf_shf(_mask)) &
(_val) : 0,"

===============================================================
__BF_FILED_CHECK {
...
  BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ?           \
                   ~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \
                   _pfx "value too large for the field"); \
...
===============================================================

Should I fix it by converting
  delay_val |= FIELD_PREP(ETH_DLY_TXC_ENABLE, !!mac_delay->tx_delay);
to
  en_val = !!mac_delay->tx_delay;
  delay_val |= FIELD_PREP(ETH_DLY_TXC_ENABLE, !!en_val);

or other suggestions for these warnings?

Thanks~

On Wed, 2021-12-08 at 06:38 -0800, Jakub Kicinski wrote:
> On Wed, 8 Dec 2021 13:47:15 +0800 Biao Huang wrote:
> > Add Ethernet support for MediaTek SoCs from the mt8195 family.
> > 
> > Signed-off-by: Biao Huang <biao.huang@...iatek.com>
> > Acked-by: AngeloGioacchino Del Regno <
> > angelogioacchino.delregno@...labora.com>
> 
> sparse reports whole bunch of warnings like this:
> 
> drivers/net/ethernet/stmicro/stmmac/dwmac-mediatek.c:213:30: warning:
> dubious: x & !y
> drivers/net/ethernet/stmicro/stmmac/dwmac-mediatek.c:217:30: warning:
> dubious: x & !y
> drivers/net/ethernet/stmicro/stmmac/dwmac-mediatek.c:228:38: warning:
> dubious: x & !y
> drivers/net/ethernet/stmicro/stmmac/dwmac-mediatek.c:232:38: warning:
> dubious: x & !y
> drivers/net/ethernet/stmicro/stmmac/dwmac-mediatek.c:247:46: warning:
> dubious: x & !y
> drivers/net/ethernet/stmicro/stmmac/dwmac-mediatek.c:255:46: warning:
> dubious: x & !y
> drivers/net/ethernet/stmicro/stmmac/dwmac-mediatek.c:273:30: warning:
> dubious: x & !y
> drivers/net/ethernet/stmicro/stmmac/dwmac-mediatek.c:277:30: warning:
> dubious: x & !y
> drivers/net/ethernet/stmicro/stmmac/dwmac-mediatek.c:375:30: warning:
> dubious: x & !y
> drivers/net/ethernet/stmicro/stmmac/dwmac-mediatek.c:379:30: warning:
> dubious: x & !y
> drivers/net/ethernet/stmicro/stmmac/dwmac-mediatek.c:390:43: warning:
> dubious: x & !y
> drivers/net/ethernet/stmicro/stmmac/dwmac-mediatek.c:397:43: warning:
> dubious: x & !y
> drivers/net/ethernet/stmicro/stmmac/dwmac-mediatek.c:415:46: warning:
> dubious: x & !y
> drivers/net/ethernet/stmicro/stmmac/dwmac-mediatek.c:426:46: warning:
> dubious: x & !y
> drivers/net/ethernet/stmicro/stmmac/dwmac-mediatek.c:439:35: warning:
> dubious: x & !y
> drivers/net/ethernet/stmicro/stmmac/dwmac-mediatek.c:443:30: warning:
> dubious: x & !y
> 
> Any idea on where these come from?