VGA library (libvga)¶

General information¶

libvga is designed to interface with VGA-compatible display hardware. This library provides both low-level hardware access and high-level functionality to manage VGA display settings, modes, and memory.

Mode Adjustment Flags¶

Adjustment flags are used to modify the behavior of the VGA display modes.

VGA_HSYNCP: Set for HSync positive polarity.

VGA_VSYNCP: Set for VSync positive polarity.

VGA_CLKDIV: Indicates the pixel clock is divided by 2.

VGA_DBLSCAN: Enables double scanning.

VGA_INTERLACE: Activates interlace mode.

Structures¶

vga_cfg_t - Holds the configuration for a VGA mode, including pixel clock, horizontal and vertical timings, and mode adjustment flags.

typedef struct {
    /* Pixel clock */
    unsigned int clkidx; /* Pixel clock source index */
    unsigned int clk;    /* Pixel clock frequency (kHz) */
    /* Horizontal timings */
    unsigned int hres;   /* Horizontal resolution */
    unsigned int hsyncs; /* Horizontal sync start */
    unsigned int hsynce; /* Horizontal sync end */
    unsigned int htotal; /* Horizontal total pixels */
    /* Vertical timings */
    unsigned int vres;   /* Vertical resolution */
    unsigned int vsyncs; /* Vertical sync start */
    unsigned int vsynce; /* Vertical sync end */
    unsigned int vtotal; /* Vertical total lines */
    /* Mode adjustments */
    unsigned char flags; /* Mode adjustment flags */
} vga_cfg_t;

vga_state_t - Represents the state of the VGA, including various registers, color map, text, and font data.

typedef struct {
    unsigned char mr;     /* Miscellaneous register */
    unsigned char cr[25]; /* CRT controller registers */
    unsigned char sr[5];  /* Sequencer registers */
    unsigned char gr[9];  /* Graphics controller registers */
    unsigned char ar[21]; /* Attribute controller registers */
    unsigned char *cmap;  /* Color map */
    unsigned char *text;  /* Plane 0 and 1 text */
    unsigned char *font1; /* Plane 2 font */
    unsigned char *font2; /* Plane 3 font */
} vga_state_t;

Low-Level Interface (Hardware Abstraction Layer)¶

Memory and Register Access¶

vgahw_mem - Returns the mapped VGA memory address.
```
void *vgahw_mem(void *hwctx)
```
vgahw_status - Reads from the input status register.
```
unsigned char vgahw_status(void *hwctx)
```
vgahw_readfcr - Read operations for the feature control register.
```
unsigned char vgahw_readfcr(void *hwctx)
```
vgahw_writefcr - Write operations for the feature control register.
```
void vgahw_writefcr(void *hwctx, unsigned char val)
```
vgahw_readmisc - Read operations for the miscellaneous register.
```
unsigned char vgahw_readmisc(void *hwctx)
```
vgahw_readmisc - Write operations for the miscellaneous register.
```
void vgahw_writemisc(void *hwctx, unsigned char val)
```

vgahw_readcrtc - Read operations for CRT controller registers.

unsigned char vgahw_readcrtc(void *hwctx, unsigned char reg)

vgahw_writecrtc - Write operations for CRT controller registers.

void vgahw_writecrtc(void *hwctx, unsigned char reg, unsigned char val)

vgahw_readseq - Read operations for sequencer registers.

unsigned char vgahw_readseq(void *hwctx, unsigned char reg)

vgahw_writeseq - Write operations for sequencer registers.

void vgahw_writeseq(void *hwctx, unsigned char reg, unsigned char val)

vgahw_readgfx - Read operations for graphics controller registers.

unsigned char vgahw_readgfx(void *hwctx, unsigned char reg)

vgahw_writegfx - Write operations for graphics controller registers.

void vgahw_writegfx(void *hwctx, unsigned char reg, unsigned char val)

vgahw_readattr - Read operations for attribute controller registers.

unsigned char vgahw_readattr(void *hwctx, unsigned char reg)

vgahw_writeattr - Write operations for attribute controller registers.

void vgahw_writeattr(void *hwctx, unsigned char reg, unsigned char val)

vgahw_readdac - Read operations for DAC controller registers.

unsigned char vgahw_readdac(void *hwctx, unsigned char reg)

vgahw_writedac - Write operations for DAC controller registers.

void vgahw_writedac(void *hwctx, unsigned char reg, unsigned char val)

Color Map Management¶

vgahw_enablecmap - Enables the color map.
```
void vgahw_enablecmap(void *hwctx)
```
vgahw_disablecmap - Disables the color map.
```
void vgahw_disablecmap(void *hwctx)
```

VGA Handle Management¶

vgahw_init - Initializes the VGA handle.
```
int vgahw_init(void *hwctx)
```
vgahw_done - Destroys the VGA handle.
```
void vgahw_done(void *hwctx)
```

High-Level Interface¶

VGA Register and Mode Management¶

vga_lock - Lock CRTC[0-7] registers.
```
void vga_lock(void *hwctx)
```
vga_unlock - Unlock CRTC[0-7] registers.
```
void vga_unlock(void *hwctx)
```
vga_mlock - Protect/release VGA registers and memory during mode switch.
```
void vga_mlock(void *hwctx)
```
vga_munlock - Protect/release VGA registers and memory during mode switch.
```
void vga_munlock(void *hwctx)
```
vga_blank - Blanks the screen.
```
void vga_blank(void *hwctx)
```
vga_unblank - Un blanks the screen.
```
void vga_unblank(void *hwctx)
```

VGA State Management¶

vga_savemode - Save the VGA mode.

void vga_savemode(void *hwctx, vga_state_t *state)

vga_restoremode - Restore the VGA mode.

void vga_restoremode(void *hwctx, vga_state_t *state)

vga_savecmap - Save the VGA color map.

void vga_savecmap(void *hwctx, vga_state_t *state)

vga_restorecmap - Restore the VGA color map.

void vga_restorecmap(void *hwctx, vga_state_t *state)

vga_savetext - Save VGA fonts and text.

void vga_savetext(void *hwctx, vga_state_t *state)

vga_restoretext - Restore VGA fonts and text.

void vga_restoretext(void *hwctx, vga_state_t *state)

vga_save - Save all VGA settings.

void vga_save(void *hwctx, vga_state_t *state)

vga_restore - Restore all VGA settings.

void vga_restore(void *hwctx, vga_state_t *state)

VGA Configuration¶

vga_initstate - Initializes the VGA state for a given mode configuration.
```
void vga_initstate(vga_cfg_t *cfg, vga_state_t *state)
```

Using libvga¶

To use functions provided by libvga please add the library to the LIBS variable in Makefile and include the required header file.