Hi
Am 14.11.25 um 09:31 schrieb Ard Biesheuvel:
On Wed, 15 Oct 2025 at 18:08, Thomas Zimmermann <[email protected]> wrote:
Add support for EFI_EDID_ACTIVE_PROTOCOL and EFI_EDID_DISCOVERED_PROTOCOL
on x86. Refactor the GOP helpers for EDID support, then retrieve the EDID
into x86 boot_params.
Later boot code copies the EDID from the boot parameters into the global
variable edid_info. Graphics drivers, such as efidrm, can pick up the
information from there. In the case of efidrm, it provides the EDID to
user-space compositors, which use it for improved QoS on the display
output. Similar functionality is already available on old VESA systems
with vesadrm.
Tested on x86 EFI systems.
Another patch is required to provide EDID on non-x86 systems via the
generic EFI stub. The implementation can directly build upon this
series.
Thomas Zimmermann (5):
efi: Fix trailing whitespace in header file
efi/libstub: gop: Find GOP handle instead of GOP data
efi/libstub: gop: Initialize screen_info in helper function
efi/libstub: gop: Add support for reading EDID
efi/libstub: x86: Store EDID in boot_params
Hi,
Apologies for the delay. This series looks fine to me, although I
would prefer it if we could make things a bit more generic?
Everything you are adding here is arch-agnostic, except for the bit
where we use x86-specific plumbing to pass the EDID info between the
EFI stub and the core kernel.
Attached is an RFC patch that I already have. This would be the next
step for EDID support. I've not yet sent the generic-EFI patch, as I did
not have opportunity to test it. The patch addresses most of what you
ask for, I think.
More specifically, could we do the following:
- move struct edid_info edid_info into common code
edid_info is related to screen_info, so it follows the same conventions.
Arnd Bergmann made x86-specific changes for screen_info in commit
b8466fe82b79 ("efi: move screen_info into efi init code"). x86 has it's
own thing, sort of. See the attached patch for my non-x86 solution.
- pass the detected EDID info block via a EFI config table instead of
boot_params
The x86 code uses boot params for screen_info already and also transfers
edid_info on VESA systems via boot params (or if grub set up boot_params
for us). [1] It's all there and working already. If we transfer
edid_info via config table, we'd need extra code on x86.
- make CONFIG_FIRMWARE_EDID depend on (X86 || EFI_STUB)
See the attached patch.
Best regards
Thomas
--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)
From 10be917b0cf90f22f2fd900620cb9acf5838ff55 Mon Sep 17 00:00:00 2001
From: Thomas Zimmermann <[email protected]>
Date: Wed, 15 Oct 2025 13:36:06 +0200
Subject: [PATCH] efi: transfer EDID from stub to kernel
- Add UUID for storing the EDID data in the UEFI configuration table.
- The UUID has been created by uuidgen.
- Enable edid_info on EFI systems
---
drivers/firmware/efi/efi-init.c | 33 +++++++++++++-
drivers/firmware/efi/efi.c | 2 +
drivers/firmware/efi/libstub/Makefile | 2 +-
drivers/firmware/efi/libstub/edid_info.c | 40 +++++++++++++++++
drivers/firmware/efi/libstub/efi-stub-entry.c | 17 +++++++
drivers/firmware/efi/libstub/efi-stub.c | 44 +++++++++++++------
drivers/firmware/efi/libstub/efistub.h | 4 ++
drivers/video/Kconfig | 8 ++--
include/linux/efi.h | 8 ++--
9 files changed, 136 insertions(+), 22 deletions(-)
create mode 100644 drivers/firmware/efi/libstub/edid_info.c
diff --git a/drivers/firmware/efi/efi-init.c b/drivers/firmware/efi/efi-init.c
index a65c2d5b9e7b..2719311f2d43 100644
--- a/drivers/firmware/efi/efi-init.c
+++ b/drivers/firmware/efi/efi-init.c
@@ -23,7 +23,10 @@
#include <asm/efi.h>
+#include <video/edid.h>
+
unsigned long __initdata screen_info_table = EFI_INVALID_TABLE_ADDR;
+unsigned long __initdata edid_info_table = EFI_INVALID_TABLE_ADDR;
static int __init is_memory(efi_memory_desc_t *md)
{
@@ -57,14 +60,19 @@ static phys_addr_t __init efi_to_phys(unsigned long addr)
extern __weak const efi_config_table_type_t efi_arch_tables[];
/*
- * x86 defines its own screen_info and uses it even without EFI,
- * everything else can get it from here.
+ * x86 defines its own screen_info and edid_info and uses them even
+ * without EFI, everything else can get them from here.
*/
#if !defined(CONFIG_X86) && (defined(CONFIG_SYSFB) || defined(CONFIG_EFI_EARLYCON))
struct screen_info screen_info __section(".data");
EXPORT_SYMBOL_GPL(screen_info);
#endif
+#if !defined(CONFIG_X86) && defined(CONFIG_FIRMWARE_EDID)
+struct edid_info edid_info __section(".data");
+EXPORT_SYMBOL_GPL(edid_info);
+#endif
+
static void __init init_screen_info(void)
{
struct screen_info *si;
@@ -88,6 +96,23 @@ static void __init init_screen_info(void)
}
}
+static void __init init_edid_info(void)
+{
+#if defined(CONFIG_FIRMWARE_EDID)
+ struct edid_info *edid;
+
+ if (edid_info_table == EFI_INVALID_TABLE_ADDR)
+ return;
+
+ edid = early_memremap(edid_info_table, sizeof(*edid));
+ if (!edid)
+ return; /* not an error; EDID is optional */
+ edid_info = *edid;
+ memset(edid, 0, sizeof(*edid));
+ early_memunmap(edid, sizeof(*edid));
+#endif
+}
+
static int __init uefi_init(u64 efi_system_table)
{
efi_config_table_t *config_tables;
@@ -275,4 +300,8 @@ void __init efi_init(void)
IS_ENABLED(CONFIG_SYSFB) ||
IS_ENABLED(CONFIG_EFI_EARLYCON))
init_screen_info();
+
+ if (IS_ENABLED(CONFIG_X86) ||
+ IS_ENABLED(CONFIG_FIRMWARE_EDID))
+ init_edid_info();
}
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 1ce428e2ac8a..7a3047a238ae 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -64,6 +64,7 @@ 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 edid_info_table;
struct mm_struct efi_mm = {
.mm_mt = MTREE_INIT_EXT(mm_mt, MM_MT_FLAGS, efi_mm.mmap_lock),
@@ -639,6 +640,7 @@ static const efi_config_table_type_t common_tables[] __initconst = {
#endif
#ifdef CONFIG_EFI_GENERIC_STUB
{LINUX_EFI_SCREEN_INFO_TABLE_GUID, &screen_info_table },
+ {LINUX_EFI_EDID_INFO_TABLE_GUID, &edid_info_table },
#endif
{},
};
diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index 94b05e4451dd..12ae5c6be028 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/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
+ screen_info.o edid_info.o efi-stub-entry.o
lib-$(CONFIG_ARM) += arm32-stub.o
lib-$(CONFIG_ARM64) += kaslr.o arm64.o arm64-stub.o smbios.o
diff --git a/drivers/firmware/efi/libstub/edid_info.c b/drivers/firmware/efi/libstub/edid_info.c
new file mode 100644
index 000000000000..882c85faf395
--- /dev/null
+++ b/drivers/firmware/efi/libstub/edid_info.c
@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/efi.h>
+#include <video/edid.h>
+#include <asm/efi.h>
+
+#include "efistub.h"
+
+static efi_guid_t edid_info_guid = LINUX_EFI_EDID_INFO_TABLE_GUID;
+
+struct edid_info *__alloc_edid_info(void)
+{
+ struct edid_info *edid;
+ efi_status_t status;
+
+ status = efi_bs_call(allocate_pool, EFI_ACPI_RECLAIM_MEMORY,
+ sizeof(*edid), (void **)&edid);
+
+ if (status != EFI_SUCCESS)
+ return NULL;
+
+ memset(edid, 0, sizeof(*edid));
+
+ status = efi_bs_call(install_configuration_table,
+ &edid_info_guid, edid);
+ if (status == EFI_SUCCESS)
+ return edid;
+
+ efi_bs_call(free_pool, edid);
+ return NULL;
+}
+
+void free_edid_info(struct edid_info *edid)
+{
+ if (!edid)
+ return;
+
+ efi_bs_call(install_configuration_table, &edid_info_guid, NULL);
+ efi_bs_call(free_pool, edid);
+}
diff --git a/drivers/firmware/efi/libstub/efi-stub-entry.c b/drivers/firmware/efi/libstub/efi-stub-entry.c
index a6c049835190..7ba8a23bbc55 100644
--- a/drivers/firmware/efi/libstub/efi-stub-entry.c
+++ b/drivers/firmware/efi/libstub/efi-stub-entry.c
@@ -5,9 +5,12 @@
#include <asm/efi.h>
+#include <video/edid.h>
+
#include "efistub.h"
static unsigned long screen_info_offset;
+static unsigned long edid_info_offset;
struct screen_info *alloc_screen_info(void)
{
@@ -22,6 +25,19 @@ struct screen_info *alloc_screen_info(void)
return NULL;
}
+struct edid_info *alloc_edid_info(void)
+{
+#if defined(CONFIG_FIRMWARE_EDID)
+ if (IS_ENABLED(CONFIG_ARM))
+ return __alloc_edid_info();
+
+ if (IS_ENABLED(CONFIG_X86) &&
+ IS_ENABLED(CONFIG_FIRMWARE_EDID))
+ return (void *)&edid_info + edid_info_offset;
+#endif
+ return NULL;
+}
+
/*
* EFI entry point for the generic EFI stub used by ARM, arm64, RISC-V and
* LoongArch. This is the entrypoint that is described in the PE/COFF header
@@ -74,6 +90,7 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
}
screen_info_offset = image_addr - (unsigned long)image->image_base;
+ edid_info_offset = image_addr - (unsigned long)image->image_base;
status = efi_stub_common(handle, image, image_addr, cmdline_ptr);
diff --git a/drivers/firmware/efi/libstub/efi-stub.c b/drivers/firmware/efi/libstub/efi-stub.c
index 9cb814c5ba1b..9cb2a5c154b4 100644
--- a/drivers/firmware/efi/libstub/efi-stub.c
+++ b/drivers/firmware/efi/libstub/efi-stub.c
@@ -12,6 +12,7 @@
#include <linux/efi.h>
#include <linux/screen_info.h>
#include <asm/efi.h>
+#include <video/edid.h>
#include "efistub.h"
@@ -49,22 +50,37 @@ 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_edid_info(struct edid_info *edid)
+{ }
-static struct screen_info *setup_graphics(void)
+static void setup_graphics(struct screen_info **si, struct edid_info **edid)
{
- struct screen_info *si, tmp = {};
+ efi_status_t status;
+
+ *si = alloc_screen_info();
+ *edid = alloc_edid_info();
- if (efi_setup_graphics(&tmp, NULL) != EFI_SUCCESS)
- return NULL;
+ if (!*si && !*edid)
+ return;
- si = alloc_screen_info();
- if (!si)
- return NULL;
+ status = efi_setup_graphics(*si, *edid);
+ if (status) {
+ /* Clear on error */
+ if (*edid)
+ memset(*edid, 0, sizeof(**edid));
+ if (*si)
+ memset(*si, 0, sizeof(**si));
+ }
+}
- *si = tmp;
- return si;
+static void release_graphics(struct screen_info *si, struct edid_info *edid)
+{
+ if (edid)
+ free_edid_info(edid);
+ if (si)
+ free_screen_info(si);
}
static void install_memreserve_table(void)
@@ -146,13 +162,14 @@ efi_status_t efi_stub_common(efi_handle_t handle,
char *cmdline_ptr)
{
struct screen_info *si;
+ struct edid_info *edid;
efi_status_t status;
status = check_platform_features();
if (status != EFI_SUCCESS)
return status;
- si = setup_graphics();
+ setup_graphics(&si, &edid);
efi_retrieve_eventlog();
@@ -172,7 +189,8 @@ efi_status_t efi_stub_common(efi_handle_t handle,
status = efi_boot_kernel(handle, image, image_addr, cmdline_ptr);
- free_screen_info(si);
+ release_graphics(si, edid);
+
return status;
}
diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
index b2fb0c3fa721..120c9a499362 100644
--- a/drivers/firmware/efi/libstub/efistub.h
+++ b/drivers/firmware/efi/libstub/efistub.h
@@ -1179,6 +1179,10 @@ struct screen_info *alloc_screen_info(void);
struct screen_info *__alloc_screen_info(void);
void free_screen_info(struct screen_info *si);
+struct edid_info *alloc_edid_info(void);
+struct edid_info *__alloc_edid_info(void);
+void free_edid_info(struct edid_info *edid);
+
void efi_cache_sync_image(unsigned long image_base,
unsigned long alloc_size);
diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
index d51777df12d1..f452fac90a9f 100644
--- a/drivers/video/Kconfig
+++ b/drivers/video/Kconfig
@@ -63,11 +63,13 @@ endif # HAS_IOMEM
config FIRMWARE_EDID
bool "Enable firmware EDID"
- depends on X86
+ depends on EFI || X86
help
This enables access to the EDID transferred from the firmware.
- On x86, this is from the VESA BIOS. DRM display drivers will
- be able to export the information to userspace.
+ On EFI systems, the EDID comes from the same device as the
+ primary GOP. On x86 with BIOS, it comes from the VESA BIOS.
+ DRM display drivers will be able to export the information
+ to userspace.
Also enable this if DDC/I2C transfers do not work for your driver
and if you are using nvidiafb, i810fb or savagefb.
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 11e267492efd..eeff8393c9c0 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -406,11 +406,13 @@ void efi_native_runtime_setup(void);
#define EFI_CC_FINAL_EVENTS_TABLE_GUID EFI_GUID(0xdd4a4648, 0x2de7, 0x4665, 0x96, 0x4d, 0x21, 0xd9, 0xef, 0x5f, 0xb4, 0x46)
/*
- * This GUID is used to pass to the kernel proper the struct screen_info
- * structure that was populated by the stub based on the GOP protocol instance
- * associated with ConOut
+ * These GUIDs are used to pass to the kernel proper the struct screen_info
+ * and struct edid_info structures that were populated by the stub based on
+ * the GOP protocol instance associated with ConOut.
*/
#define LINUX_EFI_SCREEN_INFO_TABLE_GUID EFI_GUID(0xe03fc20a, 0x85dc, 0x406e, 0xb9, 0x0e, 0x4a, 0xb5, 0x02, 0x37, 0x1d, 0x95)
+#define LINUX_EFI_EDID_INFO_TABLE_GUID EFI_GUID(0x4e6c17ea, 0x6ec0, 0x4838, 0x8c, 0xae, 0x2c, 0xf5, 0x4d, 0x5f, 0x58, 0x64)
+
#define LINUX_EFI_ARM_CPU_STATE_TABLE_GUID EFI_GUID(0xef79e4aa, 0x3c3d, 0x4989, 0xb9, 0x02, 0x07, 0xa9, 0x43, 0xe5, 0x50, 0xd2)
#define LINUX_EFI_LOADER_ENTRY_GUID EFI_GUID(0x4a67b082, 0x0a4c, 0x41cf, 0xb6, 0xc7, 0x44, 0x0b, 0x29, 0xbb, 0x8c, 0x4f)
#define LINUX_EFI_RANDOM_SEED_TABLE_GUID EFI_GUID(0x1ce1e5bc, 0x7ceb, 0x42f2, 0x81, 0xe5, 0x8a, 0xad, 0xf1, 0x80, 0xf5, 0x7b)
--
2.51.1
