Bare metal VGA: pass video mode information via struct mman

This should hopefully help us adapt the VGA console code, to
work with video modes other than 80 × 25 × 16 text.

libc/intrin/mman.greg.c

@@ -148,6 +148,12 @@ noasan textreal void __setup_mman(struct mman *mm, uint64_t *pml4t) {
   export_offsetof(struct mman, e820);
   export_offsetof(struct mman, e820_end);
   export_offsetof(struct mman, bad_idt);
+  export_offsetof(struct mman, pc_video_type);
+  export_offsetof(struct mman, pc_video_scan_width);
+  export_offsetof(struct mman, pc_video_width);
+  export_offsetof(struct mman, pc_video_height);
+  export_offsetof(struct mman, pc_video_framebuffer);
+  export_offsetof(struct mman, pc_video_framebuffer_size);
   __normalize_e820(mm);
   __invert_memory(mm, pml4t);
 }

libc/runtime/mman.internal.h

@@ -18,8 +18,25 @@ struct mman {
   unsigned char pc_drive_last_head;      /* 0x1d21 */
   unsigned char pc_drive;                /* 0x1d22 */
   char bad_idt[6];                       /* 0x1d23 */
+  unsigned char pc_video_type;           /* 0x1d29 */
+  unsigned short pc_video_scan_width;    /* 0x1d2a — line width including any
+                                                     invisible "pixels" */
+  unsigned short pc_video_width;         /* 0x1d2c — width in chars. (text)
+                                                     or pixels (graphics) */
+  unsigned short pc_video_height;        /* 0x1d2e — height in chars. (text)
+                                                     or pixels (graphics) */
+  uint32_t pc_video_framebuffer;         /* 0x1d30 */
+  uint32_t pc_video_framebuffer_size;    /* 0x1d34 */
 };
 
 COSMOPOLITAN_C_END_
 #endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
+
+/* Values for mman::pc_video_type.  TODO: implement graphics modes. */
+#define PC_VIDEO_TEXT     0
+#define PC_VIDEO_BGR565   1
+#define PC_VIDEO_BGRX5551 2
+#define PC_VIDEO_BGRX8888 3
+#define PC_VIDEO_RGBX8888 4
+
 #endif /* COSMOPOLITAN_LIBC_RUNTIME_MMAN_H_ */

libc/vga/rlinit-vga.S

@@ -25,6 +25,7 @@
 │ OTHER DEALINGS IN THE SOFTWARE.                                              │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/macros.internal.h"
+#include "libc/runtime/mman.internal.h"
 #include "libc/vga/vga.internal.h"
 
 //	Code snippet for initializing the VGA video mode for bare metal.
@@ -42,6 +43,8 @@
 //	@see	sys_writev_vga (libc/vga/writev-vga.c)
 	.section .sort.text.real.init.2,"ax",@progbits
 	.code16
+	call	_rlinit_vesafb
+	jnc	9f
 	mov	$0x4f03,%ax		# get current video mode via VESA
 	int	$0x10
 	cmp	$0x004f,%ax		# is VESA a thing here?
@@ -58,7 +61,15 @@
 	mov	$0x0500,%ax		# just make sure we are on display
 					# page 0
 2:	int	$0x10			# otherwise, change the video mode
-	mov	$0x1003,%ax		# enable/disable VGA text blinking
+	.set	mm,0x0500		# note down video mode parameters
+	movb	$PC_VIDEO_TEXT,mm+"struct mman::pc_video_type"
+	mov	$80,%ax
+	movw	%ax,mm+"struct mman::pc_video_scan_width"
+	movw	%ax,mm+"struct mman::pc_video_width"
+	movw	$25,mm+"struct mman::pc_video_height"
+	movl	$0xb8000,mm+"struct mman::pc_video_framebuffer"
+	movl	$8*(80*25*2),mm+"struct mman::pc_video_framebuffer_size"
+9:	mov	$0x1003,%ax		# enable/disable VGA text blinking
 #ifdef VGA_USE_BLINK
 	mov	$1,%bx
 #else
@@ -66,6 +77,12 @@
 #endif
 	int	$0x10
 	.previous
+	.real
+_rlinit_vesafb_stub:
+	stc
+	ret
+	.alias	_rlinit_vesafb_stub,_rlinit_vesafb
+	.previous
 	.code64
 	.section .rodata,"a",@progbits
 vga_console:

libc/vga/vga.internal.h

@@ -2,21 +2,11 @@
 #define COSMOPOLITAN_LIBC_VGA_VGA_INTERNAL_H_
 
 /*
- * VGA_TTY_HEIGHT, VGA_TTY_WIDTH, VGA_USE_WCS, & VGA_PERSNICKETY_STATUS are
+ * VGA_USE_WCS, VGA_USE_BLINK, & VGA_PERSNICKETY_STATUS are configuration
- * configuration knobs which can potentially be used to tweak the features
+ * knobs which can potentially be used to tweak the features to be compiled
- * to be compiled into our VGA teletypewriter support.
+ * into our VGA teletypewriter support.
  */
 
-/**
- * Height of the video screen, in character units.  Undefine if the height
- * may vary at runtime.
- */
-#define VGA_TTY_HEIGHT 25
-/**
- * Width of the video screen, in character units.  Undefine if the width may
- * vary at runtime.
- */
-#define VGA_TTY_WIDTH 80
 /**
  * If VGA_USE_WCS is defined, the tty code can maintain an array of the
  * Unicode characters "underlying" the 8-bit (or 9-bit) characters that are
@@ -114,12 +104,7 @@ struct VgaTextCharCell {
 
 struct Tty {
   unsigned short y, x;
-#ifndef VGA_TTY_HEIGHT
+  unsigned short yn, xn;
-  unsigned short yn;
-#endif
-#ifndef VGA_TTY_WIDTH
-  unsigned short xn;
-#endif
   uint32_t u8;
   uint32_t n8;
   uint32_t pr;

libc/vga/writev-vga.c

@@ -60,7 +60,9 @@ ssize_t sys_writev_vga(struct Fd *fd, const struct iovec *iov, int iovlen) {
 
 __attribute__((__constructor__)) static textstartup void _vga_init(void) {
   if (IsMetal()) {
-    void * const vid_buf = (void *)(BANE + 0xb8000ull);
+    struct mman *mm = (struct mman *)(BANE + 0x0500);
+    unsigned short height = mm->pc_video_height, width = mm->pc_video_width;
+    void *vid_buf = (void *)(BANE + mm->pc_video_framebuffer);
     /*
      * Get the initial cursor position from the BIOS data area.  Also get
      * the height (in scan lines) of each character; this is used to set the
@@ -78,7 +80,7 @@ __attribute__((__constructor__)) static textstartup void _vga_init(void) {
      * Initialize our tty structure from the current screen contents,
      * current cursor position, & character height.
      */
-    _StartTty(&_vga_tty, VGA_TTY_HEIGHT, VGA_TTY_WIDTH, pos.row, pos.col,
+    _StartTty(&_vga_tty, height, width, pos.row, pos.col, chr_ht,
-              chr_ht, vid_buf, vga_wcs);
+              vid_buf, vga_wcs);
   }
 }