[PATCH 2/2] dell-laptop: Expose auxiliary MAC address if available

[Mario Limonciello]

System with Type-C ports have a feature to expose an auxiliary
persistent MAC address.  This address is burned in at the
factory.

The intention of this address is to update the MAC address on
Type-C docks containing an ethernet adapter to match the
auxiliary address of the system connected to them.

Signed-off-by: Mario Limonciello <mario_limoncie...@dell.com>
---
 drivers/platform/x86/dell-laptop.c | 62 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 61 insertions(+), 1 deletion(-)

diff --git a/drivers/platform/x86/dell-laptop.c 
b/drivers/platform/x86/dell-laptop.c
index 2c2f02b..f818ddf 100644
--- a/drivers/platform/x86/dell-laptop.c
+++ b/drivers/platform/x86/dell-laptop.c
@@ -87,6 +87,7 @@ static struct rfkill *wifi_rfkill;
 static struct rfkill *bluetooth_rfkill;
 static struct rfkill *wwan_rfkill;
 static bool force_rfkill;
+static char *auxiliary_mac_address;
 
 module_param(force_rfkill, bool, 0444);
 MODULE_PARM_DESC(force_rfkill, "enable rfkill on non whitelisted models");
@@ -273,6 +274,58 @@ static const struct dmi_system_id dell_quirks[] 
__initconst = {
        { }
 };
 
+/* get_aux_mac
+ * returns the auxiliary mac address
+ * for assigning to a Type-C ethernet device
+ * such as that found in the Dell TB15 dock
+ */
+static int get_aux_mac(void)
+{
+       struct calling_interface_buffer *buffer;
+       int ret;
+       unsigned char *address =
+               (unsigned char *) __get_free_page(GFP_KERNEL | GFP_DMA32);
+
+       buffer = dell_smbios_get_buffer();
+
+       /* prepare a 17 byte buffer */
+       dell_smbios_prepare_v2_call(address, 17);
+       buffer->input[0] = virt_to_phys(address);
+       dell_smbios_send_request(11, 6);
+       ret = buffer->output[0];
+
+       if (ret != 0)
+               goto auxout;
+
+       dell_smbios_clear_buffer();
+
+       /* address will be stored in byte 4-> */
+       auxiliary_mac_address = kmalloc(13, GFP_KERNEL);
+       memcpy(auxiliary_mac_address, &address[4], 13);
+
+ auxout:
+       free_page((unsigned long)address);
+       dell_smbios_release_buffer();
+       return dell_smbios_error(ret);
+
+}
+
+static ssize_t auxiliary_mac_show(struct device *dev,
+                                 struct device_attribute *attr, char *page)
+{
+       return sprintf(page, "%s\n", auxiliary_mac_address);
+}
+
+static DEVICE_ATTR_RO(auxiliary_mac);
+static struct attribute *dell_attributes[] = {
+       &dev_attr_auxiliary_mac.attr,
+       NULL
+};
+static const struct attribute_group dell_attr_group = {
+.attrs = dell_attributes,
+};
+
+
 /*
  * Derived from information in smbios-wireless-ctl:
  *
@@ -392,7 +445,6 @@ static const struct dmi_system_id dell_quirks[] __initconst 
= {
  *     cbArg1, byte0 = 0x13
  *     cbRes1 Standard return codes (0, -1, -2)
  */
-
 static int dell_rfkill_set(void *data, bool blocked)
 {
        struct calling_interface_buffer *buffer;
@@ -2003,6 +2055,12 @@ static int __init dell_init(void)
                goto fail_rfkill;
        }
 
+       ret = get_aux_mac();
+       if (!ret) {
+               sysfs_create_group(&platform_device->dev.kobj,
+                                  &dell_attr_group);
+       }
+
        if (quirks && quirks->touchpad_led)
                touchpad_led_init(&platform_device->dev);
 
@@ -2048,6 +2106,7 @@ static int __init dell_init(void)
                backlight_update_status(dell_backlight_device);
        }
 
+
        return 0;
 
 fail_backlight:
@@ -2064,6 +2123,7 @@ fail_platform_driver:
 
 static void __exit dell_exit(void)
 {
+       kfree(auxiliary_mac_address);
        debugfs_remove_recursive(dell_laptop_dir);
        if (quirks && quirks->touchpad_led)
                touchpad_led_exit();
-- 
2.7.4