Video mode probing support for the new x86 setup code

Video mode probing for the new x86 setup code.  This code breaks down
different drivers into modules.  This code deliberately drops support
for a lot of the vendor-specific mode probing present in the assembly
version, since a lot of those probes have been found to be stale in
current versions of those chips -- frequently, support for those modes
have been dropped from recent video BIOSes due to space constraints,
but the video BIOS signatures are still the same.

However, additional drivers should be extremely straightforward to plug
in, if desirable.

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

1 files changed, 125 insertions, 0 deletions

diff --git a/arch/i386/boot/video-bios.c b/arch/i386/boot/video-bios.c
new file mode 100644
index 000000000000..afea46c500cc
--- /dev/null
+++ b/arch/i386/boot/video-bios.c
@@ -0,0 +1,125 @@
+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ *   Copyright (C) 1991, 1992 Linus Torvalds
+ *   Copyright 2007 rPath, Inc. - All Rights Reserved
+ *
+ *   This file is part of the Linux kernel, and is made available under
+ *   the terms of the GNU General Public License version 2.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * arch/i386/boot/video-bios.c
+ *
+ * Standard video BIOS modes
+ *
+ * We have two options for this; silent and scanned.
+ */
+
+#include "boot.h"
+#include "video.h"
+
+__videocard video_bios;
+
+/* Set a conventional BIOS mode */
+static int set_bios_mode(u8 mode);
+
+static int bios_set_mode(struct mode_info *mi)
+{
+        return set_bios_mode(mi->mode - VIDEO_FIRST_BIOS);
+}
+
+static int set_bios_mode(u8 mode)
+{
+        u16 ax;
+        u8 new_mode;
+
+        ax = mode;              /* AH=0x00 Set Video Mode */
+        asm volatile(INT10
+                     : "+a" (ax)
+                     : : "ebx", "ecx", "edx", "esi", "edi");
+
+        ax = 0x0f00;            /* Get Current Video Mode */
+        asm volatile(INT10
+                     : "+a" (ax)
+                     : : "ebx", "ecx", "edx", "esi", "edi");
+
+        do_restore = 1;         /* Assume video contents was lost */
+        new_mode = ax & 0x7f;   /* Not all BIOSes are clean with the top bit */
+
+        if (new_mode == mode)
+                return 0;       /* Mode change OK */
+
+        if (new_mode != boot_params.screen_info.orig_video_mode) {
+                /* Mode setting failed, but we didn't end up where we
+                   started.  That's bad.  Try to revert to the original
+                   video mode. */
+                ax = boot_params.screen_info.orig_video_mode;
+                asm volatile(INT10
+                             : "+a" (ax)
+                             : : "ebx", "ecx", "edx", "esi", "edi");
+        }
+        return -1;
+}
+
+static int bios_probe(void)
+{
+        u8 mode;
+        u8 saved_mode = boot_params.screen_info.orig_video_mode;
+        u16 crtc;
+        struct mode_info *mi;
+        int nmodes = 0;
+
+        if (adapter != ADAPTER_EGA && adapter != ADAPTER_VGA)
+                return 0;
+
+        set_fs(0);
+        crtc = vga_crtc();
+
+        video_bios.modes = GET_HEAP(struct mode_info, 0);
+
+        for (mode = 0x14; mode <= 0x7f; mode++) {
+                if (heap_free() < sizeof(struct mode_info))
+                        break;
+
+                if (mode_defined(VIDEO_FIRST_BIOS+mode))
+                        continue;
+
+                if (set_bios_mode(mode))
+                        continue;
+
+                /* Try to verify that it's a text mode. */
+
+                /* Attribute Controller: make graphics controller disabled */
+                if (in_idx(0x3c0, 0x10) & 0x01)
+                        continue;
+
+                /* Graphics Controller: verify Alpha addressing enabled */
+                if (in_idx(0x3ce, 0x06) & 0x01)
+                        continue;
+
+                /* CRTC cursor location low should be zero(?) */
+                if (in_idx(crtc, 0x0f))
+                        continue;
+
+                mi = GET_HEAP(struct mode_info, 1);
+                mi->mode = VIDEO_FIRST_BIOS+mode;
+                mi->x = rdfs16(0x44a);
+                mi->y = rdfs8(0x484)+1;
+                nmodes++;
+        }
+
+        set_bios_mode(saved_mode);
+
+        return nmodes;
+}
+
+__videocard video_bios =
+{
+        .card_name      = "BIOS (scanned)",
+        .probe          = bios_probe,
+        .set_mode       = bios_set_mode,
+        .unsafe         = 1,
+        .xmode_first    = VIDEO_FIRST_BIOS,
+        .xmode_n        = 0x80,
+};