Bluetooth: hci_bcm: Fall back to getting bdaddr from EFI if not set

On some devices the BCM Bluetooth adapter does not have a valid bdaddr set.

btbcm.c currently sets HCI_QUIRK_INVALID_BDADDR to indicate when this is
the case. But this requires users to manual setup a btaddr, by doing e.g.:

btmgmt -i hci0 public-addr 'B0:F1:EC:82:1D:B3'

Which means that Bluetooth will not work out of the box on such devices.
To avoid this (where possible) hci_bcm sets: HCI_QUIRK_USE_BDADDR_PROPERTY
which tries to get the bdaddr from devicetree.

But this only works on devicetree platforms. On UEFI based platforms
there is a special Broadcom UEFI variable which when present contains
the devices bdaddr, just like how there is another UEFI variable which
contains wifi nvram contents including the wifi MAC address.

Add support for getting the bdaddr from this Broadcom UEFI variable,
so that Bluetooth will work OOTB for users on devices where this
UEFI variable is present.

This fixes Bluetooth not working on for example Asus T100HA 2-in-1s.

Signed-off-by: Hans de Goede <[e-mail]>
Signed-off-by: Luiz Augusto von Dentz <[e-mail]>

drivers/bluetooth/btbcm.c

···
  *  Copyright (C) 2015  Intel Corporation
  */
 
+#include <linux/efi.h>
 #include <linux/module.h>
 #include <linux/firmware.h>
 #include <linux/dmi.h>
···
 #define BCM_FW_NAME_COUNT_MAX		4
 /* For kmalloc-ing the fw-name array instead of putting it on the stack */
 typedef char bcm_fw_name[BCM_FW_NAME_LEN];
+
+#ifdef CONFIG_EFI
+static int btbcm_set_bdaddr_from_efi(struct hci_dev *hdev)
+{
+	efi_guid_t guid = EFI_GUID(0x74b00bd9, 0x805a, 0x4d61, 0xb5, 0x1f,
+				   0x43, 0x26, 0x81, 0x23, 0xd1, 0x13);
+	bdaddr_t efi_bdaddr, bdaddr;
+	efi_status_t status;
+	unsigned long len;
+	int ret;
+
+	if (!efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE))
+		return -EOPNOTSUPP;
+
+	len = sizeof(efi_bdaddr);
+	status = efi.get_variable(L"BDADDR", &guid, NULL, &len, &efi_bdaddr);
+	if (status != EFI_SUCCESS)
+		return -ENXIO;
+
+	if (len != sizeof(efi_bdaddr))
+		return -EIO;
+
+	baswap(&bdaddr, &efi_bdaddr);
+
+	ret = btbcm_set_bdaddr(hdev, &bdaddr);
+	if (ret)
+		return ret;
+
+	bt_dev_info(hdev, "BCM: Using EFI device address (%pMR)", &bdaddr);
+	return 0;
+}
+#else
+static int btbcm_set_bdaddr_from_efi(struct hci_dev *hdev)
+{
+	return -EOPNOTSUPP;
+}
+#endif
 
 int btbcm_check_bdaddr(struct hci_dev *hdev)
 {
···
 	    !bacmp(&bda->bdaddr, BDADDR_BCM4345C5) ||
 	    !bacmp(&bda->bdaddr, BDADDR_BCM43430A0) ||
 	    !bacmp(&bda->bdaddr, BDADDR_BCM43341B)) {
-		bt_dev_info(hdev, "BCM: Using default device address (%pMR)",
-			    &bda->bdaddr);
-		set_bit(HCI_QUIRK_INVALID_BDADDR, &hdev->quirks);
+		/* Try falling back to BDADDR EFI variable */
+		if (btbcm_set_bdaddr_from_efi(hdev) != 0) {
+			bt_dev_info(hdev, "BCM: Using default device address (%pMR)",
+				    &bda->bdaddr);
+			set_bit(HCI_QUIRK_INVALID_BDADDR, &hdev->quirks);
+		}
 	}
 
 	kfree_skb(skb);