fbdev: Add support for the nomodeset kernel parameter

Support the kernel's nomodeset parameter for all PCI-based fbdev
drivers that use aperture helpers to remove other, hardware-agnostic
graphics drivers.

The parameter is a simple way of using the firmware-provided scanout
buffer if the hardware's native driver is broken. The same effect
could be achieved with per-driver options, but the importance of the
graphics output for many users makes a single, unified approach
worthwhile.

With nomodeset specified, the fbdev driver module will not load. This
unifies behavior with similar DRM drivers. In DRM helpers, modules
first check the nomodeset parameter before registering the PCI
driver. As fbdev has no such module helpers, we have to modify each
driver individually.

The name 'nomodeset' is slightly misleading, but has been chosen for
historical reasons. Several drivers implemented it before it became a
general option for DRM. So keeping the existing name was preferred over
introducing a new one.

v2:
	* print a warning if a driver does not init (Helge)
	* wrap video_firmware_drivers_only() in helper

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221111133024.9897-3-tzimmermann@suse.de

4 files changed, 18 insertions, 0 deletions

diff --git a/drivers/video/fbdev/geode/Kconfig b/drivers/video/fbdev/geode/Kconfig
index ac9c860592aa..2f8f0fb1dae2 100644
--- a/drivers/video/fbdev/geode/Kconfig
+++ b/drivers/video/fbdev/geode/Kconfig
@@ -15,6 +15,7 @@ config FB_GEODE_LX
 	select FB_CFB_FILLRECT
 	select FB_CFB_COPYAREA
 	select FB_CFB_IMAGEBLIT
+	select VIDEO_NOMODESET
 	help
 	  Framebuffer driver for the display controller integrated into the
 	  AMD Geode LX processors.
@@ -30,6 +31,7 @@ config FB_GEODE_GX
 	select FB_CFB_FILLRECT
 	select FB_CFB_COPYAREA
 	select FB_CFB_IMAGEBLIT
+	select VIDEO_NOMODESET
 	help
 	  Framebuffer driver for the display controller integrated into the
 	  AMD Geode GX processors.
@@ -45,6 +47,7 @@ config FB_GEODE_GX1
 	select FB_CFB_FILLRECT
 	select FB_CFB_COPYAREA
 	select FB_CFB_IMAGEBLIT
+	select VIDEO_NOMODESET
 	help
 	  Framebuffer driver for the display controller integrated into the
 	  AMD Geode GX1 processor.
diff --git a/drivers/video/fbdev/geode/gx1fb_core.c b/drivers/video/fbdev/geode/gx1fb_core.c
index 1514c653a84f..9c942001ac10 100644
--- a/drivers/video/fbdev/geode/gx1fb_core.c
+++ b/drivers/video/fbdev/geode/gx1fb_core.c
@@ -446,7 +446,12 @@ static int __init gx1fb_init(void)
 {
 #ifndef MODULE
 	char *option = NULL;
+#endif
+
+	if (fb_modesetting_disabled("gx1fb"))
+		return -ENODEV;
 
+#ifndef MODULE
 	if (fb_get_options("gx1fb", &option))
 		return -ENODEV;
 	gx1fb_setup(option);
diff --git a/drivers/video/fbdev/geode/gxfb_core.c b/drivers/video/fbdev/geode/gxfb_core.c
index 2527bd80ec5f..8e05e76de075 100644
--- a/drivers/video/fbdev/geode/gxfb_core.c
+++ b/drivers/video/fbdev/geode/gxfb_core.c
@@ -511,7 +511,12 @@ static int __init gxfb_init(void)
 {
 #ifndef MODULE
 	char *option = NULL;
+#endif
+
+	if (fb_modesetting_disabled("gxfb"))
+		return -ENODEV;
 
+#ifndef MODULE
 	if (fb_get_options("gxfb", &option))
 		return -ENODEV;
 
diff --git a/drivers/video/fbdev/geode/lxfb_core.c b/drivers/video/fbdev/geode/lxfb_core.c
index 9d26592dbfce..8130e9eee2b4 100644
--- a/drivers/video/fbdev/geode/lxfb_core.c
+++ b/drivers/video/fbdev/geode/lxfb_core.c
@@ -647,7 +647,12 @@ static int __init lxfb_init(void)
 {
 #ifndef MODULE
 	char *option = NULL;
+#endif
+
+	if (fb_modesetting_disabled("lxfb"))
+		return -ENODEV;
 
+#ifndef MODULE
 	if (fb_get_options("lxfb", &option))
 		return -ENODEV;