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>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/x86/boot/video-vesa.c b/arch/x86/boot/video-vesa.c
index 1e6fe02..99b3079 100644 (file)
--- 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 3b296e4..6210755 100644 (file)
--- 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
@@ -681,6 +689,7 @@ config FB_VESA
        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 generic VESA 2.0
          compliant graphic cards. The older VESA 1.2 cards are not supported.
@@ -1117,6 +1126,7 @@ 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.
@@ -1469,6 +1479,7 @@ 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.