stdvga: Add comments to interface functions in stdvga.c
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
diff --git a/vgasrc/stdvga.c b/vgasrc/stdvga.c
index eac0357..149c88a 100644
--- a/vgasrc/stdvga.c
+++ b/vgasrc/stdvga.c
@@ -1,6 +1,6 @@
// Standard VGA driver code
//
-// Copyright (C) 2009 Kevin O'Connor <kevin@koconnor.net>
+// Copyright (C) 2009-2024 Kevin O'Connor <kevin@koconnor.net>
// Copyright (C) 2001-2008 the LGPL VGABios developers Team
//
// This file may be distributed under the terms of the GNU LGPLv3 license.
@@ -44,29 +44,35 @@
stdvga_attr_mask(i, 0x01, palid & 0x01);
}
+// Set the VGA palette index register for the "overscan" area
void
stdvga_set_overscan_border_color(u8 color)
{
stdvga_attr_write(0x11, color);
}
+// Get the VGA palette index register for the "overscan" area
u8
stdvga_get_overscan_border_color(void)
{
return stdvga_attr_read(0x11);
}
+// Set the VGA palette index registers
void
stdvga_set_all_palette_reg(u16 seg, u8 *data_far)
{
+ // Set palette indexes (offset into DAC colors)
int i;
for (i = 0; i < 0x10; i++) {
stdvga_attr_write(i, GET_FARVAR(seg, *data_far));
data_far++;
}
+ // Set "overscan" palette index (offset into DAC colors)
stdvga_attr_write(0x11, GET_FARVAR(seg, *data_far));
}
+// Get the VGA palette index registers
void
stdvga_get_all_palette_reg(u16 seg, u8 *data_far)
{
@@ -78,6 +84,7 @@
SET_FARVAR(seg, *data_far, stdvga_attr_read(0x11));
}
+// Set blinking mode (when enabled, palette index bit 0x08 indicates blinking)
void
stdvga_toggle_intensity(u8 flag)
{
@@ -116,6 +123,7 @@
* DAC control
****************************************************************/
+// Convert all loaded colors to shades of gray
void
stdvga_perform_gray_scale_summing(u16 start, u16 count)
{
@@ -141,6 +149,7 @@
* Memory control
****************************************************************/
+// Set the video memory location of the start of character fonts
void
stdvga_set_text_block_specifier(u8 spec)
{
@@ -210,6 +219,7 @@
* CRTC registers
****************************************************************/
+// Return the IO port used to access the CRTC register
u16
stdvga_get_crtc(void)
{
@@ -234,6 +244,7 @@
}
}
+// Set cursor shape (when in text mode)
void
stdvga_set_cursor_shape(u16 cursor_type)
{
@@ -242,6 +253,7 @@
stdvga_crtc_write(crtc_addr, 0x0b, cursor_type);
}
+// Set the position of the text cursor (as offset into system framebuffer)
void
stdvga_set_cursor_pos(int address)
{
@@ -251,6 +263,7 @@
stdvga_crtc_write(crtc_addr, 0x0f, address);
}
+// Set the character height (when in text mode)
void
stdvga_set_scan_lines(u8 lines)
{
@@ -268,15 +281,19 @@
return vde;
}
+// Get offset into framebuffer accessible from real-mode 64K segment
int
stdvga_get_window(struct vgamode_s *curmode_g, int window)
{
return -1;
}
+// Set offset into framebuffer that is accessible from real-mode 64K
+// segment (in units of VBE_win_granularity windows)
int
stdvga_set_window(struct vgamode_s *curmode_g, int window, int val)
{
+ // Stdvga does not support changing window offset
return -1;
}
@@ -325,15 +342,18 @@
return 0;
}
+// Report if using 8bit per rgb (24bit total) or 6bit per rgb (18bit total)
int
stdvga_get_dacformat(struct vgamode_s *curmode_g)
{
return -1;
}
+// Set 8bit per rgb (24bit total) or 6bit per rgb (18bit total)
int
stdvga_set_dacformat(struct vgamode_s *curmode_g, int val)
{
+ // Stdvga only supports 6bits for each color channel
return -1;
}
@@ -477,6 +497,7 @@
* Misc
****************************************************************/
+// Enable/disable system access to the video memory
void
stdvga_enable_video_addressing(u8 disable)
{
