efi: Support EDID information

In the EFI config table, rename LINUX_EFI_SCREEN_INFO_TABLE_GUID to
LINUX_EFI_PRIMARY_DISPLAY_TABLE_GUID. Read sysfb_primary_display from
the entry. In addition to the screen_info, the entry now also contains
EDID information.

In libstub, replace struct screen_info with struct sysfb_display_info
from the kernel's sysfb_primary_display and rename functions
accordingly.  Transfer it to the runtime kernel using the kernel's
global state or the LINUX_EFI_PRIMARY_DISPLAY_TABLE_GUID config-table
entry.

With CONFIG_FIRMWARE_EDID=y, libstub now transfers the GOP device's EDID
information to the kernel. If CONFIG_FIRMWARE_EDID=n, EDID information
is disabled. Make the Kconfig symbol CONFIG_FIRMWARE_EDID available with
EFI. Setting the value to 'n' disables EDID support.

Also rename screen_info.c to primary_display.c and adapt the contained
comment according to the changes.

Link: https://lore.kernel.org/all/20251126160854.553077-8-tzimmermann@suse.de/
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
[ardb: depend on EFI_GENERIC_STUB not EFI, fix conflicts after dropping
       the preceding patch from the series]
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Author: tdz

arch/loongarch/kernel/efi.c

@@ -72,7 +72,7 @@ bool efi_poweroff_required(void)
 		(acpi_gbl_reduced_hardware || acpi_no_s5);
 }
 
-unsigned long __initdata screen_info_table = EFI_INVALID_TABLE_ADDR;
+unsigned long __initdata primary_display_table = EFI_INVALID_TABLE_ADDR;
 
 #if defined(CONFIG_SYSFB) || defined(CONFIG_EFI_EARLYCON)
 struct sysfb_display_info sysfb_primary_display __section(".data");
@@ -81,19 +81,19 @@ EXPORT_SYMBOL_GPL(sysfb_primary_display);
 
 static void __init init_primary_display(void)
 {
-	struct screen_info *si;
+	struct sysfb_display_info *dpy;
 
-	if (screen_info_table == EFI_INVALID_TABLE_ADDR)
+	if (primary_display_table == EFI_INVALID_TABLE_ADDR)
 		return;
 
-	si = early_memremap(screen_info_table, sizeof(*si));
-	if (!si) {
-		pr_err("Could not map screen_info config table\n");
+	dpy = early_memremap(primary_display_table, sizeof(*dpy));
+	if (!dpy) {
+		pr_err("Could not map primary_display config table\n");
 		return;
 	}
-	sysfb_primary_display.screen = *si;
-	memset(si, 0, sizeof(*si));
-	early_memunmap(si, sizeof(*si));
+	sysfb_primary_display = *dpy;
+	memset(dpy, 0, sizeof(*dpy));
+	early_memunmap(dpy, sizeof(*dpy));
 
 	memblock_reserve(__screen_info_lfb_base(&sysfb_primary_display.screen),
 			 sysfb_primary_display.screen.lfb_size);

drivers/firmware/efi/efi-init.c

@@ -23,7 +23,7 @@
 
 #include <asm/efi.h>
 
-unsigned long __initdata screen_info_table = EFI_INVALID_TABLE_ADDR;
+unsigned long __initdata primary_display_table = EFI_INVALID_TABLE_ADDR;
 
 static int __init is_memory(efi_memory_desc_t *md)
 {
@@ -67,17 +67,17 @@ EXPORT_SYMBOL_GPL(sysfb_primary_display);
 
 static void __init init_primary_display(void)
 {
-	struct screen_info *si;
+	struct sysfb_display_info *dpy;
 
-	if (screen_info_table != EFI_INVALID_TABLE_ADDR) {
-		si = early_memremap(screen_info_table, sizeof(*si));
-		if (!si) {
-			pr_err("Could not map screen_info config table\n");
+	if (primary_display_table != EFI_INVALID_TABLE_ADDR) {
+		dpy = early_memremap(primary_display_table, sizeof(*dpy));
+		if (!dpy) {
+			pr_err("Could not map primary_display config table\n");
 			return;
 		}
-		sysfb_primary_display.screen = *si;
-		memset(si, 0, sizeof(*si));
-		early_memunmap(si, sizeof(*si));
+		sysfb_primary_display = *dpy;
+		memset(dpy, 0, sizeof(*dpy));
+		early_memunmap(dpy, sizeof(*dpy));
 
 		if (memblock_is_map_memory(sysfb_primary_display.screen.lfb_base))
 			memblock_mark_nomap(sysfb_primary_display.screen.lfb_base,

drivers/firmware/efi/efi.c

@@ -63,7 +63,7 @@ static unsigned long __initdata mem_reserve = EFI_INVALID_TABLE_ADDR;
 static unsigned long __initdata rt_prop = EFI_INVALID_TABLE_ADDR;
 static unsigned long __initdata initrd = EFI_INVALID_TABLE_ADDR;
 
-extern unsigned long screen_info_table;
+extern unsigned long primary_display_table;
 
 struct mm_struct efi_mm = {
 	.mm_mt			= MTREE_INIT_EXT(mm_mt, MM_MT_FLAGS, efi_mm.mmap_lock),
@@ -641,7 +641,7 @@ static const efi_config_table_type_t common_tables[] __initconst = {
 	{LINUX_EFI_UNACCEPTED_MEM_TABLE_GUID,	&efi.unaccepted,	"Unaccepted"	},
 #endif
 #ifdef CONFIG_EFI_GENERIC_STUB
-	{LINUX_EFI_SCREEN_INFO_TABLE_GUID,	&screen_info_table			},
+	{LINUX_EFI_PRIMARY_DISPLAY_TABLE_GUID,	&primary_display_table			},
 #endif
 	{},
 };

drivers/firmware/efi/libstub/Makefile

@@ -80,7 +80,7 @@ $(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
 	$(call if_changed_rule,cc_o_c)
 
 lib-$(CONFIG_EFI_GENERIC_STUB)	+= efi-stub.o string.o intrinsics.o systable.o \
-				   screen_info.o efi-stub-entry.o
+				   primary_display.o efi-stub-entry.o
 
 lib-$(CONFIG_ARM)		+= arm32-stub.o
 lib-$(CONFIG_ARM64)		+= kaslr.o arm64.o arm64-stub.o smbios.o

drivers/firmware/efi/libstub/efi-stub-entry.c

@@ -14,18 +14,15 @@ static void *kernel_image_addr(void *addr)
 	return addr + kernel_image_offset;
 }
 
-struct screen_info *alloc_screen_info(void)
+struct sysfb_display_info *alloc_primary_display(void)
 {
 	if (IS_ENABLED(CONFIG_ARM))
-		return __alloc_screen_info();
+		return __alloc_primary_display();
 
 	if (IS_ENABLED(CONFIG_X86) ||
 	    IS_ENABLED(CONFIG_EFI_EARLYCON) ||
-	    IS_ENABLED(CONFIG_SYSFB)) {
-		struct sysfb_display_info *dpy = kernel_image_addr(&sysfb_primary_display);
-
-		return &dpy->screen;
-	}
+	    IS_ENABLED(CONFIG_SYSFB))
+		return kernel_image_addr(&sysfb_primary_display);
 
 	return NULL;
 }

drivers/firmware/efi/libstub/efi-stub.c

@@ -10,7 +10,7 @@
  */
 
 #include <linux/efi.h>
-#include <linux/screen_info.h>
+#include <linux/sysfb.h>
 #include <asm/efi.h>
 
 #include "efistub.h"
@@ -48,23 +48,33 @@
 static u64 virtmap_base = EFI_RT_VIRTUAL_BASE;
 static bool flat_va_mapping = (EFI_RT_VIRTUAL_OFFSET != 0);
 
-void __weak free_screen_info(struct screen_info *si)
-{
-}
+void __weak free_primary_display(struct sysfb_display_info *dpy)
+{ }
 
-static struct screen_info *setup_graphics(void)
+static struct sysfb_display_info *setup_primary_display(void)
 {
-	struct screen_info *si, tmp = {};
+	struct sysfb_display_info *dpy;
+	struct screen_info *screen = NULL;
+	struct edid_info *edid = NULL;
+	efi_status_t status;
 
-	if (efi_setup_graphics(&tmp, NULL) != EFI_SUCCESS)
+	dpy = alloc_primary_display();
+	if (!dpy)
 		return NULL;
+	screen = &dpy->screen;
+#if defined(CONFIG_FIRMWARE_EDID)
+	edid = &dpy->edid;
+#endif
 
-	si = alloc_screen_info();
-	if (!si)
-		return NULL;
+	status = efi_setup_graphics(screen, edid);
+	if (status != EFI_SUCCESS)
+		goto err_free_primary_display;
 
-	*si = tmp;
-	return si;
+	return dpy;
+
+err_free_primary_display:
+	free_primary_display(dpy);
+	return NULL;
 }
 
 static void install_memreserve_table(void)
@@ -145,14 +155,14 @@ efi_status_t efi_stub_common(efi_handle_t handle,
 			     unsigned long image_addr,
 			     char *cmdline_ptr)
 {
-	struct screen_info *si;
+	struct sysfb_display_info *dpy;
 	efi_status_t status;
 
 	status = check_platform_features();
 	if (status != EFI_SUCCESS)
 		return status;
 
-	si = setup_graphics();
+	dpy = setup_primary_display();
 
 	efi_retrieve_eventlog();
 
@@ -172,7 +182,8 @@ efi_status_t efi_stub_common(efi_handle_t handle,
 
 	status = efi_boot_kernel(handle, image, image_addr, cmdline_ptr);
 
-	free_screen_info(si);
+	free_primary_display(dpy);
+
 	return status;
 }
 

drivers/firmware/efi/libstub/efistub.h

@@ -36,6 +36,7 @@
 
 struct edid_info;
 struct screen_info;
+struct sysfb_display_info;
 
 extern bool efi_no5lvl;
 extern bool efi_nochunk;
@@ -1175,9 +1176,9 @@ efi_enable_reset_attack_mitigation(void) { }
 
 void efi_retrieve_eventlog(void);
 
-struct screen_info *alloc_screen_info(void);
-struct screen_info *__alloc_screen_info(void);
-void free_screen_info(struct screen_info *si);
+struct sysfb_display_info *alloc_primary_display(void);
+struct sysfb_display_info *__alloc_primary_display(void);
+void free_primary_display(struct sysfb_display_info *dpy);
 
 void efi_cache_sync_image(unsigned long image_base,
 			  unsigned long alloc_size);

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);
+}

drivers/firmware/efi/libstub/screen_info.c

@@ -26,9 +26,9 @@ void __weak efi_cache_sync_image(unsigned long image_base,
 	// executable code loaded into memory to be safe for execution.
 }
 
-struct screen_info *alloc_screen_info(void)
+struct sysfb_display_info *alloc_primary_display(void)
 {
-	return __alloc_screen_info();
+	return __alloc_primary_display();
 }
 
 asmlinkage efi_status_t __efiapi