sysfb: Fix screen_info type check for VGA

commit f670b50ef5e4a69bf4d2ec5ac6a9228d93b13a7a upstream.

Use the helper screen_info_video_type() to get the framebuffer
type from struct screen_info. Handle supported values in sorted
switch statement.

Reading orig_video_isVGA is unreliable. On most systems it is a
VIDEO_TYPE_ constant. On some systems with VGA it is simply set
to 1 to signal the presence of a VGA output. See vga_probe() for
an example. Retrieving the screen_info type with the helper
screen_info_video_type() detects these cases and returns the
appropriate VIDEO_TYPE_ constant. For VGA, sysfb creates a device
named "vga-framebuffer".

The sysfb code has been taken from vga16fb, where it likely didn't
work correctly either. With this bugfix applied, vga16fb loads for
compatible vga-framebuffer devices.

Fixes: 0db5b61e0dc0 ("fbdev/vga16fb: Create EGA/VGA devices in sysfb code")
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Javier Martinez Canillas <javierm@redhat.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Tzung-Bi Shih <tzungbi@kernel.org>
Cc: Helge Deller <deller@gmx.de>
Cc: "Uwe Kleine-König" <u.kleine-koenig@baylibre.com>
Cc: Zsolt Kajtar <soci@c64.rulez.org>
Cc: <stable@vger.kernel.org> # v6.1+
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://lore.kernel.org/r/20250603154838.401882-1-tzimmermann@suse.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 18 insertions, 8 deletions

diff --git a/drivers/firmware/sysfb.c b/drivers/firmware/sysfb.c
index a3df782fa687..e919940c8bf9 100644
--- a/drivers/firmware/sysfb.c
+++ b/drivers/firmware/sysfb.c
@@ -124,6 +124,7 @@ static __init int sysfb_init(void)
 {
 	struct screen_info *si = &screen_info;
 	struct device *parent;
+	unsigned int type;
 	struct simplefb_platform_data mode;
 	const char *name;
 	bool compatible;
@@ -151,17 +152,26 @@ static __init int sysfb_init(void)
 			goto put_device;
 	}
 
+	type = screen_info_video_type(si);
+
 	/* if the FB is incompatible, create a legacy framebuffer device */
-	if (si->orig_video_isVGA == VIDEO_TYPE_EFI)
-		name = "efi-framebuffer";
-	else if (si->orig_video_isVGA == VIDEO_TYPE_VLFB)
-		name = "vesa-framebuffer";
-	else if (si->orig_video_isVGA == VIDEO_TYPE_VGAC)
-		name = "vga-framebuffer";
-	else if (si->orig_video_isVGA == VIDEO_TYPE_EGAC)
+	switch (type) {
+	case VIDEO_TYPE_EGAC:
 		name = "ega-framebuffer";
-	else
+		break;
+	case VIDEO_TYPE_VGAC:
+		name = "vga-framebuffer";
+		break;
+	case VIDEO_TYPE_VLFB:
+		name = "vesa-framebuffer";
+		break;
+	case VIDEO_TYPE_EFI:
+		name = "efi-framebuffer";
+		break;
+	default:
 		name = "platform-framebuffer";
+		break;
+	}
 
 	pd = platform_device_alloc(name, 0);
 	if (!pd) {