From 1f2fcbbca18176e2e6c862774428dad878bbac51 Mon Sep 17 00:00:00 2001
From: Michael Marineau <address@hidden>
Date: Sun, 30 Mar 2014 13:01:35 -0700
Subject: [PATCH] efi: Identify as OS X to EFI drivers before booting.

This prevents the firmware from powering down the integrated graphics
card on some recent 2013 Macbook Pro laptops. The trick was originally
posted as a command for GRUB2 by Andreas Heider.

http://lists.gnu.org/archive/html/grub-devel/2013-12/msg00442.html
---
 arch/x86/boot/compressed/eboot.c | 62 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)

diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index 1acf605..419b368 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -1374,6 +1374,66 @@ free_mem_map:
 	return status;
 }
 
+#define APPLE_SET_OS_PROTOCOL_GUID \
+	EFI_GUID(0xc5c5da95, 0x7d5c, 0x45e6, 0xb2, 0xf1, 0x3f, 0xd5, 0x2b, 0xb1, 0x00, 0x77)
+
+typedef struct {
+	u64 version;
+	void (*set_os_version) (const char *os_version);
+	void (*set_os_vendor) (const char *os_vendor);
+} apple_set_os_interface_t;
+
+static efi_status_t apple_set_os()
+{
+	apple_set_os_interface_t *set_os;
+	efi_guid_t set_os_guid = APPLE_SET_OS_PROTOCOL_GUID;
+	efi_status_t status;
+	void **handles;
+	unsigned long i, nr_handles, size = 0;
+
+	status = efi_call_early(locate_handle, EFI_LOCATE_BY_PROTOCOL,
+				&set_os_guid, NULL, &size, handles);
+
+	if (status == EFI_BUFFER_TOO_SMALL) {
+		status = efi_call_early(allocate_pool, EFI_LOADER_DATA,
+					size, &handles);
+
+		if (status != EFI_SUCCESS)
+			return status;
+
+		status = efi_call_early(locate_handle, EFI_LOCATE_BY_PROTOCOL,
+					&set_os_guid, NULL, &size, handles);
+	}
+
+	if (status != EFI_SUCCESS)
+		goto free_handle;
+
+	nr_handles = size / sizeof(void *);
+	for (i = 0; i < nr_handles; i++) {
+		void *h = handles[i];
+
+		status = efi_call_early(handle_protocol, h,
+					&set_os_guid, &set_os);
+
+		if (status != EFI_SUCCESS || !set_os)
+			continue;
+
+		if (set_os->version > 0) {
+			efi_early->call((unsigned long)set_os->set_os_version,
+					"Mac OS X 10.9");
+		}
+
+		if (set_os->version >= 2) {
+			efi_early->call((unsigned long)set_os->set_os_vendor,
+					"Apple Inc.");
+		}
+	}
+
+free_handle:
+	efi_call_early(free_pool, handles);
+	return status;
+}
+
 /*
  * On success we return a pointer to a boot_params structure, and NULL
  * on failure.
@@ -1445,6 +1505,8 @@ struct boot_params *efi_main(struct efi_config *c,
 		hdr->code32_start = bzimage_addr;
 	}
 
+	apple_set_os();
+
 	status = exit_boot(boot_params, handle, is64);
 	if (status != EFI_SUCCESS) {
 		efi_printk(sys_table, "exit_boot() failed!\n");
-- 
2.0.4