1 files changed, 56 insertions, 0 deletions
diff --git a/drivers/firmware/efi/libstub/primary_display.c b/drivers/firmware/efi/libstub/primary_display.c
new file mode 100644
index 000000000000..cdaebab26514
--- /dev/null
+++ b/drivers/firmware/efi/libstub/primary_display.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/efi.h>
+#include <linux/sysfb.h>
+
+#include <asm/efi.h>
+
+#include "efistub.h"
+
+/*
+ * There are two ways of populating the core kernel's sysfb_primary_display
+ * via the stub:
+ *
+ *   - using a configuration table, which relies on the EFI init code to
+ *     locate the table and copy the contents; or
+ *
+ *   - by linking directly to the core kernel's copy of the global symbol.
+ *
+ * The latter is preferred because it makes the EFIFB earlycon available very
+ * early, but it only works if the EFI stub is part of the core kernel image
+ * itself. The zboot decompressor can only use the configuration table
+ * approach.
+ */
+
+static efi_guid_t primary_display_guid = LINUX_EFI_PRIMARY_DISPLAY_TABLE_GUID;
+
+struct sysfb_display_info *__alloc_primary_display(void)
+{
+	struct sysfb_display_info *dpy;
+	efi_status_t status;
+
+	status = efi_bs_call(allocate_pool, EFI_ACPI_RECLAIM_MEMORY,
+			     sizeof(*dpy), (void **)&dpy);
+
+	if (status != EFI_SUCCESS)
+		return NULL;
+
+	memset(dpy, 0, sizeof(*dpy));
+
+	status = efi_bs_call(install_configuration_table,
+			     &primary_display_guid, dpy);
+	if (status == EFI_SUCCESS)
+		return dpy;
+
+	efi_bs_call(free_pool, dpy);
+	return NULL;
+}
+
+void free_primary_display(struct sysfb_display_info *dpy)
+{
+	if (!dpy)
+		return;
+
+	efi_bs_call(install_configuration_table, &primary_display_guid, NULL);
+	efi_bs_call(free_pool, dpy);
+}