Re: [PATCH net-next] net: dsa: yt921x: Fix missing type casting to u64
From: David Laight <hidden>
Date: 2025-10-24 12:21:21
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On Fri, 24 Oct 2025 16:49:13 +0800 David Yang [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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 <redacted> Closes: https://lore.kernel.org/netdev/aPsjYKQMzpY0nSXm@stanley.mountain/ (local) Signed-off-by: David Yang <mmyangfl@gmail.com> --- 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);