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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-47496afd459sm87470645e9.1.2025.10.24.05.21.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 24 Oct 2025 05:21:19 -0700 (PDT) Date: Fri, 24 Oct 2025 13:21:17 +0100 From: David Laight To: David Yang Cc: netdev@vger.kernel.org, Dan Carpenter , Andrew Lunn , Vladimir Oltean , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next] net: dsa: yt921x: Fix missing type casting to u64 Message-ID: <20251024132117.43f39504@pumpkin> In-Reply-To: <20251024084918.1353031-1-mmyangfl@gmail.com> References: <20251024084918.1353031-1-mmyangfl@gmail.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 24 Oct 2025 16:49:13 +0800 David Yang wrote: > Reported by the following Smatch static checker warning: > > drivers/net/dsa/yt921x.c:702 yt921x_read_mib() > warn: was expecting a 64 bit value instead of '(~0)' > > Reported-by: Dan Carpenter > Closes: https://lore.kernel.org/netdev/aPsjYKQMzpY0nSXm@stanley.mountain/ > Signed-off-by: David Yang > --- > drivers/net/dsa/yt921x.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/net/dsa/yt921x.c b/drivers/net/dsa/yt921x.c > index ab762ffc4661..8baed8107512 100644 > --- a/drivers/net/dsa/yt921x.c > +++ b/drivers/net/dsa/yt921x.c > @@ -699,7 +699,7 @@ static int yt921x_read_mib(struct yt921x_priv *priv, int port) > if (val < (u32)val) That check is wrong as well, probably (val0 < (u32)val) is right. But the code is confusing. > /* overflow */ > val += (u64)U32_MAX + 1; > - val &= ~U32_MAX; > + val &= ~(u64)U32_MAX; > val |= val0; How about: if (desc->size <= 1) { u64 old_val = *valp; val = upper32_bits(old_val) | val0; if (val < old_val) val += 1ull << 32; } There is also an inconsistency with the read of *valp and the WRITE_ONCE() lower down. If there is a READ_ONCE() elsewhere then it not going to work on 32bit architectures - since both the read and write are still likely to be two memory cycles. David > } else { > res = yt921x_reg_read(priv, reg + 4, &val1);