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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org References: <20250708190635.GW452973@horms.kernel.org> Content-Language: en-US In-Reply-To: <20250708190635.GW452973@horms.kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit >> - if ((old_vid != (u16)E1000_MNG_VLAN_NONE) && >> + if ((old_vid != E1000_MNG_VLAN_NONE) && > > Ditto. > > But more importantly, both Clang 20.1.7 W=1 builds (or at any rate, > builds with -Wtautological-constant-out-of-range-compare), and Smatch > complain that the comparison above is now always true because > E1000_MNG_VLAN_NONE is -1, while old_vid is unsigned. You are right - I have missed that E1000_MNG_VLAN_NONE is negative. Therefore (u16)E1000_MNG_VLAN_NONE has a side effect of causing a wraparound. It's even more interesting that (inadvertently) I have not made a similar change in e1000e: ./drivers/net/ethernet/intel/e1000e/netdev.c: if (adapter->mng_vlan_id != (u16)E1000_MNG_VLAN_NONE) { > Perhaps E1000_MNG_VLAN_NONE should be updated to be UINT16_MAX? There's no UINT16_MAX in kernel as far as I know. I'd rather leave it as it was or, if you insist on further refactoring, use either one of: #define E1000_MNG_VLAN_NONE (u16)(~((u16) 0)) mimick ACPI: #define ACPI_UINT16_MAX (u16)(~((u16) 0)) #define E1000_MNG_VLAN_NONE ((u16)-1) move the cast into the constant #define E1000_MNG_VLAN_NONE 0xFFFF use ready-made value (parentheses left only due to the constant being "(-1)" and not "-1"). -- Best regards, Jacek Kowalski