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Subject[PATCH v3] fbdev: ignore VESA modes if framebuffer does not support them
Currently, it is possible to set a graphics VESA mode at boot time via
the vga= parameter even when no framebuffer driver supporting this is
configured. This could lead to the system booting with a black screen,
without a usable console.

Fix this problem by only allowing to set graphics modes at boot time
if a supporting framebuffer driver is configured.

Signed-off-by: Michal Januszewski <spock@gentoo.org>
Acked-by: Krzysztof Helt <krzysztof.h1@wp.pl>
---
This version of the patch replaces the FB_SUPPORTS_BOOT_VESA macro from
screen-info.h with a config option in drivers/video/Kconfig.
diff --git a/arch/x86/boot/video-vesa.c b/arch/x86/boot/video-vesa.c
index 401ad99..47e5080 100644
--- a/arch/x86/boot/video-vesa.c
+++ b/arch/x86/boot/video-vesa.c
@@ -88,14 +88,11 @@ static int vesa_probe(void)
(vminfo.memory_layout == 4 ||
vminfo.memory_layout == 6) &&
vminfo.memory_planes == 1) {
-#ifdef CONFIG_FB
+#ifdef CONFIG_FB_BOOT_VESA_SUPPORT
/* Graphics mode, color, linear frame buffer
supported. Only register the mode if
if framebuffer is configured, however,
- otherwise the user will be left without a screen.
- We don't require CONFIG_FB_VESA, however, since
- some of the other framebuffer drivers can use
- this mode-setting, too. */
+ otherwise the user will be left without a screen. */
mi = GET_HEAP(struct mode_info, 1);
mi->mode = mode + VIDEO_FIRST_VESA;
mi->depth = vminfo.bpp;
@@ -133,10 +130,12 @@ static int vesa_set_mode(struct mode_info *mode)
if ((vminfo.mode_attr & 0x15) == 0x05) {
/* It's a supported text mode */
is_graphic = 0;
+#ifdef CONFIG_FB_BOOT_VESA_SUPPORT
} else if ((vminfo.mode_attr & 0x99) == 0x99) {
/* It's a graphics mode with linear frame buffer */
is_graphic = 1;
vesa_mode |= 0x4000; /* Request linear frame buffer */
+#endif
} else {
return -1; /* Invalid mode */
}
diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
index 70d135e..651249d 100644
--- a/drivers/video/Kconfig
+++ b/drivers/video/Kconfig
@@ -76,6 +76,14 @@ config FB_DDC
select I2C
default n

+config FB_BOOT_VESA_SUPPORT
+ bool
+ depends on FB
+ default n
+ ---help---
+ If true, at least one selected framebuffer driver can take advantage
+ of VESA video modes set at an early boot stage via the vga= parameter.
+
config FB_CFB_FILLRECT
tristate
depends on FB
@@ -679,6 +687,7 @@ config FB_VESA
select FB_CFB_COPYAREA
select FB_CFB_IMAGEBLIT
select VIDEO_SELECT
+ select FB_BOOT_VESA_SUPPORT
help
This is the frame buffer device driver for generic VESA 2.0
compliant graphic cards. The older VESA 1.2 cards are not supported.
@@ -702,6 +711,7 @@ config FB_IMAC
select FB_CFB_FILLRECT
select FB_CFB_COPYAREA
select FB_CFB_IMAGEBLIT
+ select FB_BOOT_VESA_SUPPORT
help
This is the frame buffer device driver for the Intel-based Macintosh

@@ -1124,6 +1134,7 @@ config FB_INTEL
select FB_CFB_FILLRECT
select FB_CFB_COPYAREA
select FB_CFB_IMAGEBLIT
+ select FB_BOOT_VESA_SUPPORT
help
This driver supports the on-board graphics built in to the Intel
830M/845G/852GM/855GM/865G/915G/915GM/945G/945GM/965G/965GM chipsets.
@@ -1476,6 +1487,7 @@ config FB_SIS
select FB_CFB_FILLRECT
select FB_CFB_COPYAREA
select FB_CFB_IMAGEBLIT
+ select FB_BOOT_VESA_SUPPORT
help
This is the frame buffer device driver for the SiS 300, 315, 330
and 340 series as well as XGI V3XT, V5, V8, Z7 graphics chipsets.


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