linux-kernel - [PATCH 2/3] video/edid: Use getter function for edid

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Message-ID: <20251119123011.1187249-7-ardb+git@google.com>
Date: Wed, 19 Nov 2025 13:30:14 +0100
From: Ard Biesheuvel <ardb+git@...gle.com>
To: linux-efi@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, Javier Martinez Canillas <javierm@...hat.com>
Subject: [PATCH 2/3] video/edid: Use getter function for edid_info

From: Ard Biesheuvel <ardb@...nel.org>

Avoid accessing a global writable buffer directly for edid_info, and
instead, define a getter function returning a pointer to it. And
considering that all callers access only the 'dummy' field, just
return a const u8* directly.

This will be used by non-x86 EFI systems that pass edid_info via a EFI
configuration table.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/x86/kernel/setup.c          | 8 ++++++--
 drivers/gpu/drm/sysfb/efidrm.c   | 4 ++--
 drivers/gpu/drm/sysfb/vesadrm.c  | 4 ++--
 drivers/video/fbdev/core/fbmon.c | 4 ++--
 include/video/edid.h             | 2 +-
 5 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 1b2edd07a3e1..526c9c4553c1 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -214,8 +214,12 @@ arch_initcall(init_x86_sysctl);
 struct screen_info screen_info;
 EXPORT_SYMBOL(screen_info);
 #if defined(CONFIG_FIRMWARE_EDID)
-struct edid_info edid_info;
-EXPORT_SYMBOL_GPL(edid_info);
+static struct edid_info edid_info __ro_after_init;
+const u8 *get_edid_info(void)
+{
+	return edid_info.dummy;
+}
+EXPORT_SYMBOL_GPL(get_edid_info);
 #endif
 
 extern int root_mountflags;
diff --git a/drivers/gpu/drm/sysfb/efidrm.c b/drivers/gpu/drm/sysfb/efidrm.c
index 1883c4a8604c..e30b93ed4264 100644
--- a/drivers/gpu/drm/sysfb/efidrm.c
+++ b/drivers/gpu/drm/sysfb/efidrm.c
@@ -203,8 +203,8 @@ static struct efidrm_device *efidrm_device_create(struct drm_driver *drv,
 		&format->format, width, height, stride);
 
 #if defined(CONFIG_FIRMWARE_EDID)
-	if (drm_edid_header_is_valid(edid_info.dummy) == 8)
-		sysfb->edid = edid_info.dummy;
+	if (drm_edid_header_is_valid(get_edid_info()) == 8)
+		sysfb->edid = get_edid_info();
 #endif
 	sysfb->fb_mode = drm_sysfb_mode(width, height, 0, 0);
 	sysfb->fb_format = format;
diff --git a/drivers/gpu/drm/sysfb/vesadrm.c b/drivers/gpu/drm/sysfb/vesadrm.c
index 16a4b52d45c6..a4ff78fddc0c 100644
--- a/drivers/gpu/drm/sysfb/vesadrm.c
+++ b/drivers/gpu/drm/sysfb/vesadrm.c
@@ -469,8 +469,8 @@ static struct vesadrm_device *vesadrm_device_create(struct drm_driver *drv,
 	}
 
 #if defined(CONFIG_FIRMWARE_EDID)
-	if (drm_edid_header_is_valid(edid_info.dummy) == 8)
-		sysfb->edid = edid_info.dummy;
+	if (drm_edid_header_is_valid(get_edid_info()) == 8)
+		sysfb->edid = get_edid_info();
 #endif
 	sysfb->fb_mode = drm_sysfb_mode(width, height, 0, 0);
 	sysfb->fb_format = format;
diff --git a/drivers/video/fbdev/core/fbmon.c b/drivers/video/fbdev/core/fbmon.c
index 0a65bef01e3c..caa057c76a88 100644
--- a/drivers/video/fbdev/core/fbmon.c
+++ b/drivers/video/fbdev/core/fbmon.c
@@ -1495,7 +1495,7 @@ const unsigned char *fb_firmware_edid(struct device *device)
 {
 	struct pci_dev *dev = NULL;
 	struct resource *res = NULL;
-	unsigned char *edid = NULL;
+	const unsigned char *edid = NULL;
 
 	if (device)
 		dev = to_pci_dev(device);
@@ -1504,7 +1504,7 @@ const unsigned char *fb_firmware_edid(struct device *device)
 		res = &dev->resource[PCI_ROM_RESOURCE];
 
 	if (res && res->flags & IORESOURCE_ROM_SHADOW)
-		edid = edid_info.dummy;
+		edid = get_edid_info();
 
 	return edid;
 }
diff --git a/include/video/edid.h b/include/video/edid.h
index c2b186b1933a..b8f24c4b2829 100644
--- a/include/video/edid.h
+++ b/include/video/edid.h
@@ -5,7 +5,7 @@
 #include <uapi/video/edid.h>
 
 #if defined(CONFIG_FIRMWARE_EDID)
-extern struct edid_info edid_info;
+const u8 *get_edid_info(void) __attribute_const__;
 #endif
 
 #endif /* __linux_video_edid_h__ */
-- 
2.52.0.rc1.455.g30608eb744-goog