Re: [Intel-wired-lan] [PATCH iwl-next] igc: Support ACPI-based MAC passthrough

["Chia-Lin Kao \(AceLan\) via Intel-wired-lan" <intel-wired-lan@osuosl.org>]

On Wed, Jul 08, 2026 at 04:44:24PM +0300, Dima Ruinskiy wrote:
> Some systems implement a system MAC address object in the ACPI table,
> using either \\_SB.AMAC or \\MACA object names. This system MAC address,
> when enabled, is intended to override the permanent MAC address of the
> network controller.
>
> Implement lookup of the relevant ACPI object names and use them to
> initialize the MAC address.
>
> On systems where the feature is disabled or unsupported, the ACPI objects
> do not exist or do not contain a valid Ethernet MAC, causing a fallback
> to the existing MAC address initialization path.
This patch works as expected and solves the connection issue when the
MAC passthrough feature is enabled.

Tested-by: Chia-Lin Kao (AceLan) <acelan.kao@canonical.com>
>
> Assisted-by: GitHub-Copilot:claude-opus-4.7
> Signed-off-by: Dima Ruinskiy <dima.ruinskiy@intel.com>
> ---
>  drivers/net/ethernet/intel/igc/igc_main.c | 64 ++++++++++++++++++++++-
>  1 file changed, 62 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
> index 82800a4a6d6c..83eb8953e954 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -11,6 +11,8 @@
>  #include <net/pkt_sched.h>
>  #include <linux/bpf_trace.h>
>  #include <net/xdp_sock_drv.h>
> +#include <linux/acpi.h>
> +#include <linux/hex.h>
>  #include <linux/pci.h>
>  #include <linux/mdio.h>
>
> @@ -7116,6 +7118,57 @@ static enum hrtimer_restart igc_qbv_scheduling_timer(struct hrtimer *timer)
>  	return HRTIMER_NORESTART;
>  }
>
> +static bool igc_get_acpi_mac_passthru(u8 *mac)
> +{
> +	static const struct {
> +		const char *name;
> +		acpi_object_type type;
> +		u32 length;
> +	} sources[] = {
> +		{ "\\_SB.AMAC", ACPI_TYPE_BUFFER, 23 },
> +		{ "\\MACA",     ACPI_TYPE_STRING, 22 },
> +	};
> +	struct acpi_buffer buffer;
> +	union acpi_object *obj;
> +	bool mac_found = false;
> +	acpi_status status;
> +	u8 buf[ETH_ALEN];
> +	int i;
> +
> +	if (!IS_ENABLED(CONFIG_ACPI))
> +		return false;
> +
> +	for (i = 0; i < ARRAY_SIZE(sources) && !mac_found; i++) {
> +		buffer.length = ACPI_ALLOCATE_BUFFER;
> +		buffer.pointer = NULL;
> +
> +		status = acpi_evaluate_object(NULL, (char *)sources[i].name,
> +					      NULL, &buffer);
> +		if (ACPI_FAILURE(status))
> +			continue;
> +
> +		obj = buffer.pointer;
> +		if (!obj || obj->type != sources[i].type ||
> +		    obj->string.length != sources[i].length)
> +			goto free_obj;
> +
> +		if (strncmp(obj->string.pointer, "_AUXMAC_#", 9) ||
> +		    obj->string.pointer[21] != '#')
> +			goto free_obj;
> +
> +		if (hex2bin(buf, obj->string.pointer + 9, ETH_ALEN) ||
> +		    !is_valid_ether_addr(buf))
> +			goto free_obj;
> +
> +		ether_addr_copy(mac, buf);
> +		mac_found = true;
> +free_obj:
> +		kfree(obj);
> +	}
> +
> +	return mac_found;
> +}
> +
>  /**
>   * igc_probe - Device Initialization Routine
>   * @pdev: PCI device information struct
> @@ -7279,9 +7332,16 @@ static int igc_probe(struct pci_dev *pdev,
>  	}
>
>  	if (eth_platform_get_mac_address(&pdev->dev, hw->mac.addr)) {
> -		/* copy the MAC address out of the NVM */
> -		if (hw->mac.ops.read_mac_addr(hw))
> +		/* Look for a system-provided MAC in the ACPI table before
> +		 * falling back to reading the address from the NVM.
> +		 */
> +		if (igc_get_acpi_mac_passthru(hw->mac.addr)) {
> +			netdev->addr_assign_type = NET_ADDR_STOLEN;
> +			dev_info(&pdev->dev, "Using ACPI pass-thru MAC addr %pM\n",
> +				 hw->mac.addr);
> +		} else if (hw->mac.ops.read_mac_addr(hw)) {
>  			dev_err(&pdev->dev, "NVM Read Error\n");
> +		}
>  	}
>
>  	eth_hw_addr_set(netdev, hw->mac.addr);
> --
> 2.44.0
>