platform/x86: thinkpad_acpi: sysfs interface to auxmac

Newer Thinkpads have a feature called MAC Address Pass-through.
This patch provides a sysfs interface that userspace can use
to get this auxiliary mac address.

Signed-off-by: Fernando Eckhardt Valle <fevalle@ipt.br>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20230926202144.5906-1-fevalle@ipt.br
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

diff --git a/Documentation/admin-guide/laptops/thinkpad-acpi.rst b/Documentation/admin-guide/laptops/thinkpad-acpi.rst
index e27a1c3f634e0d0799e6b2f616e4c50f2128757d..98d30401017012212797f54627dc6ca4443cd889 100644 (file)
--- a/Documentation/admin-guide/laptops/thinkpad-acpi.rst
+++ b/Documentation/admin-guide/laptops/thinkpad-acpi.rst
@@ -53,6 +53,7 @@ detailed description):
        - Lap mode sensor
        - Setting keyboard language
        - WWAN Antenna type
+       - Auxmac
 
 A compatibility table by model and feature is maintained on the web
 site, http://ibm-acpi.sf.net/. I appreciate any success or failure
@@ -1511,6 +1512,25 @@ Currently 2 antenna types are supported as mentioned below:
 The property is read-only. If the platform doesn't have support the sysfs
 class is not created.
 
+Auxmac
+------
+
+sysfs: auxmac
+
+Some newer Thinkpads have a feature called MAC Address Pass-through. This
+feature is implemented by the system firmware to provide a system unique MAC,
+that can override a dock or USB ethernet dongle MAC, when connected to a
+network. This property enables user-space to easily determine the MAC address
+if the feature is enabled.
+
+The values of this auxiliary MAC are:
+
+        cat /sys/devices/platform/thinkpad_acpi/auxmac
+
+If the feature is disabled, the value will be 'disabled'.
+
+This property is read-only.
+
 Adaptive keyboard
 -----------------
 

diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c
index d70c89d3253440b725bf32791a8f0d1a49f408d6..9c19624a745436ea862dae758e94343ef7310e3a 100644 (file)
--- a/drivers/platform/x86/thinkpad_acpi.c
+++ b/drivers/platform/x86/thinkpad_acpi.c
@@ -10785,6 +10785,89 @@ static struct ibm_struct dprc_driver_data = {
        .name = "dprc",
 };
 
+/*
+ * Auxmac
+ *
+ * This auxiliary mac address is enabled in the bios through the
+ * MAC Address Pass-through feature. In most cases, there are three
+ * possibilities: Internal Mac, Second Mac, and disabled.
+ *
+ */
+
+#define AUXMAC_LEN 12
+#define AUXMAC_START 9
+#define AUXMAC_STRLEN 22
+#define AUXMAC_BEGIN_MARKER 8
+#define AUXMAC_END_MARKER 21
+
+static char auxmac[AUXMAC_LEN + 1];
+
+static int auxmac_init(struct ibm_init_struct *iibm)
+{
+       acpi_status status;
+       struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+       union acpi_object *obj;
+
+       status = acpi_evaluate_object(NULL, "\\MACA", NULL, &buffer);
+
+       if (ACPI_FAILURE(status))
+               return -ENODEV;
+
+       obj = buffer.pointer;
+
+       if (obj->type != ACPI_TYPE_STRING || obj->string.length != AUXMAC_STRLEN) {
+               pr_info("Invalid buffer for MAC address pass-through.\n");
+               goto auxmacinvalid;
+       }
+
+       if (obj->string.pointer[AUXMAC_BEGIN_MARKER] != '#' ||
+           obj->string.pointer[AUXMAC_END_MARKER] != '#') {
+               pr_info("Invalid header for MAC address pass-through.\n");
+               goto auxmacinvalid;
+       }
+
+       if (strncmp(obj->string.pointer + AUXMAC_START, "XXXXXXXXXXXX", AUXMAC_LEN) != 0)
+               strscpy(auxmac, obj->string.pointer + AUXMAC_START, sizeof(auxmac));
+       else
+               strscpy(auxmac, "disabled", sizeof(auxmac));
+
+free:
+       kfree(obj);
+       return 0;
+
+auxmacinvalid:
+       strscpy(auxmac, "unavailable", sizeof(auxmac));
+       goto free;
+}
+
+static struct ibm_struct auxmac_data = {
+       .name = "auxmac",
+};
+
+static ssize_t auxmac_show(struct device *dev,
+                          struct device_attribute *attr,
+                          char *buf)
+{
+       return sysfs_emit(buf, "%s\n", auxmac);
+}
+static DEVICE_ATTR_RO(auxmac);
+
+static umode_t auxmac_attr_is_visible(struct kobject *kobj,
+                                     struct attribute *attr, int n)
+{
+       return auxmac[0] == 0 ? 0 : attr->mode;
+}
+
+static struct attribute *auxmac_attributes[] = {
+       &dev_attr_auxmac.attr,
+       NULL
+};
+
+static const struct attribute_group auxmac_attr_group = {
+       .is_visible = auxmac_attr_is_visible,
+       .attrs = auxmac_attributes,
+};
+
 /* --------------------------------------------------------------------- */
 
 static struct attribute *tpacpi_driver_attributes[] = {
@@ -10843,6 +10926,7 @@ static const struct attribute_group *tpacpi_groups[] = {
        &proxsensor_attr_group,
        &kbdlang_attr_group,
        &dprc_attr_group,
+       &auxmac_attr_group,
        NULL,
 };
 
@@ -11414,6 +11498,10 @@ static struct ibm_init_struct ibms_init[] __initdata = {
                .init = tpacpi_dprc_init,
                .data = &dprc_driver_data,
        },
+       {
+               .init = auxmac_init,
+               .data = &auxmac_data,
+       },
 };
 
 static int __init set_ibm_param(const char *val, const struct kernel_param *kp)