| 1 | VBE Display API
|
|---|
| 2 | -------------------------------------------------------------------------------------------------------------
|
|---|
| 3 | This document is part of the Bochs/VBEBios documentation,
|
|---|
| 4 | it specifies the bochs host <-> vbebios client communication.
|
|---|
| 5 |
|
|---|
| 6 | That means, the display code implementation and the vbebios code depend
|
|---|
| 7 | very heavily on each other. As such, this documents needs be synchronised
|
|---|
| 8 | between bochs CVS and the vgabios CVS.
|
|---|
| 9 |
|
|---|
| 10 | This document does not describe how the VBEBios implements the VBE2/3 spec.
|
|---|
| 11 | This document does not describe how the Bochs display code will display gfx based upon this spec.
|
|---|
| 12 |
|
|---|
| 13 |
|
|---|
| 14 | API History
|
|---|
| 15 | -----------
|
|---|
| 16 | 0xb0c0 supports the following VBE_DISPI_ interfaces (present in Bochs 1.4):
|
|---|
| 17 | VBE_DISPI_INDEX_ID
|
|---|
| 18 | VBE_DISPI_INDEX_XRES
|
|---|
| 19 | VBE_DISPI_INDEX_YRES
|
|---|
| 20 | VBE_DISPI_INDEX_BPP
|
|---|
| 21 | VBE_DISPI_INDEX_ENABLE
|
|---|
| 22 | VBE_DISPI_INDEX_BANK
|
|---|
| 23 |
|
|---|
| 24 | Bpp format supported is:
|
|---|
| 25 | VBE_DISPI_BPP_8
|
|---|
| 26 |
|
|---|
| 27 | 0xb0c1 supports 0xb0c0 VBE_DISPI_ interfaces, additional interfaces (present in Bochs 2.0):
|
|---|
| 28 | VBE_DISPI_INDEX_VIRT_WIDTH
|
|---|
| 29 | VBE_DISPI_INDEX_VIRT_HEIGHT
|
|---|
| 30 | VBE_DISPI_INDEX_X_OFFSET
|
|---|
| 31 | VBE_DISPI_INDEX_Y_OFFSET
|
|---|
| 32 |
|
|---|
| 33 | 0xb0c2 supports 0xb0c1 VBE_DISPI_ interfaces, interfaces updated for
|
|---|
| 34 | additional features (present in Bochs 2.1):
|
|---|
| 35 | VBE_DISPI_INDEX_BPP supports >8bpp color depth (value = bits)
|
|---|
| 36 | VBE_DISPI_INDEX_ENABLE supports new flags VBE_DISPI_NOCLEARMEM and VBE_DISPI_LFB_ENABLED
|
|---|
| 37 | VBE i/o registers changed from 0xFF80/81 to 0x01CE/CF
|
|---|
| 38 |
|
|---|
| 39 | 0xb0c3 supports 0xb0c2 VBE_DISPI_ interfaces, interfaces updated for
|
|---|
| 40 | additional features:
|
|---|
| 41 | VBE_DISPI_INDEX_ENABLE supports new flags VBE_DISPI_GETCAPS and VBE_DISPI_8BIT_DAC
|
|---|
| 42 |
|
|---|
| 43 | 0xb0c4 VBE video memory increased to 8 MB
|
|---|
| 44 |
|
|---|
| 45 |
|
|---|
| 46 | History
|
|---|
| 47 | -------
|
|---|
| 48 | Version 0.6 2002 Nov 23 Jeroen Janssen
|
|---|
| 49 | - Added LFB support
|
|---|
| 50 | - Added Virt width, height and x,y offset
|
|---|
| 51 |
|
|---|
| 52 | Version 0.5 2002 March 08 Jeroen Janssen
|
|---|
| 53 | - Added documentation about panic behaviour / current limits of the data values.
|
|---|
| 54 | - Changed BPP API (in order to include future (A)RGB formats)
|
|---|
| 55 | - Initial version (based upon extended display text of the vbe bochs display patch)
|
|---|
| 56 |
|
|---|
| 57 |
|
|---|
| 58 | Todo
|
|---|
| 59 | ----
|
|---|
| 60 | Version 0.6+ [random order]
|
|---|
| 61 | - Add lots of different (A)RGB formats
|
|---|
| 62 |
|
|---|
| 63 | References
|
|---|
| 64 | ----------
|
|---|
| 65 | [VBE3] VBE 3 Specification at
|
|---|
| 66 | http://www.vesa.org/vbe3.pdf
|
|---|
| 67 |
|
|---|
| 68 | [BOCHS] Bochs Open Source IA-32 Emulator at
|
|---|
| 69 | http://bochs.sourceforge.net
|
|---|
| 70 |
|
|---|
| 71 | [VBEBIOS] VBE Bios for Bochs at
|
|---|
| 72 | http://savannah.gnu.org/projects/vgabios/
|
|---|
| 73 |
|
|---|
| 74 | [Screenshots] Screenshots of programs using the VBE Bios at
|
|---|
| 75 | http://japj.org/projects/bochs_plex86/screenshots.html
|
|---|
| 76 |
|
|---|
| 77 | Abbreviations
|
|---|
| 78 | -------------
|
|---|
| 79 | VBE Vesa Bios Extension
|
|---|
| 80 | DISPI (Bochs) Display Interface
|
|---|
| 81 | BPP Bits Per Pixel
|
|---|
| 82 | LFB Linear Frame Buffer
|
|---|
| 83 |
|
|---|
| 84 |
|
|---|
| 85 | #defines
|
|---|
| 86 | --------
|
|---|
| 87 | vbetables-gen.c
|
|---|
| 88 | #define VBE_DISPI_TOTAL_VIDEO_MEMORY_MB 8
|
|---|
| 89 |
|
|---|
| 90 | vbe.h
|
|---|
| 91 | #define VBE_DISPI_BANK_ADDRESS 0xA0000
|
|---|
| 92 | #define VBE_DISPI_BANK_SIZE_KB 64
|
|---|
| 93 |
|
|---|
| 94 | #define VBE_DISPI_MAX_XRES 1024
|
|---|
| 95 | #define VBE_DISPI_MAX_YRES 768
|
|---|
| 96 |
|
|---|
| 97 | #define VBE_DISPI_IOPORT_INDEX 0x01CE
|
|---|
| 98 | #define VBE_DISPI_IOPORT_DATA 0x01CF
|
|---|
| 99 |
|
|---|
| 100 | #define VBE_DISPI_INDEX_ID 0x0
|
|---|
| 101 | #define VBE_DISPI_INDEX_XRES 0x1
|
|---|
| 102 | #define VBE_DISPI_INDEX_YRES 0x2
|
|---|
| 103 | #define VBE_DISPI_INDEX_BPP 0x3
|
|---|
| 104 | #define VBE_DISPI_INDEX_ENABLE 0x4
|
|---|
| 105 | #define VBE_DISPI_INDEX_BANK 0x5
|
|---|
| 106 | #define VBE_DISPI_INDEX_VIRT_WIDTH 0x6
|
|---|
| 107 | #define VBE_DISPI_INDEX_VIRT_HEIGHT 0x7
|
|---|
| 108 | #define VBE_DISPI_INDEX_X_OFFSET 0x8
|
|---|
| 109 | #define VBE_DISPI_INDEX_Y_OFFSET 0x9
|
|---|
| 110 |
|
|---|
| 111 | #define VBE_DISPI_ID0 0xB0C0
|
|---|
| 112 | #define VBE_DISPI_ID1 0xB0C1
|
|---|
| 113 | #define VBE_DISPI_ID2 0xB0C2
|
|---|
| 114 | #define VBE_DISPI_ID3 0xB0C3
|
|---|
| 115 | #define VBE_DISPI_ID4 0xB0C4
|
|---|
| 116 |
|
|---|
| 117 | #define VBE_DISPI_DISABLED 0x00
|
|---|
| 118 | #define VBE_DISPI_ENABLED 0x01
|
|---|
| 119 | #define VBE_DISPI_VBE_ENABLED 0x40
|
|---|
| 120 | #define VBE_DISPI_NOCLEARMEM 0x80
|
|---|
| 121 |
|
|---|
| 122 | #define VBE_DISPI_LFB_PHYSICAL_ADDRESS 0xE0000000
|
|---|
| 123 |
|
|---|
| 124 | API
|
|---|
| 125 | ---
|
|---|
| 126 | The display api works by using a index (VBE_DISPI_IOPORT_INDEX) and
|
|---|
| 127 | data (VBE_DISPI_IOPORT_DATA) ioport. One writes the index of the parameter to the index port.
|
|---|
| 128 | Next, the parameter value can be read or written.
|
|---|
| 129 |
|
|---|
| 130 | [0xb0c0]
|
|---|
| 131 | * VBE_DISPI_INDEX_ID : WORD {R,W}
|
|---|
| 132 | This parameter can be used to detect the current display API (both bochs & vbebios).
|
|---|
| 133 | The bios writes VBE_DISPI_ID0 to the dataport and reads it back again.
|
|---|
| 134 | This way, the display code knows the vbebios 'ID' and the vbebios can check if the correct
|
|---|
| 135 | display code is present.
|
|---|
| 136 | As a result, a PANIC can be generated if an incompatible vbebios/display code combination is detected.
|
|---|
| 137 | This panic can be generated from the bochs display code (NOT the bios, see Notes).
|
|---|
| 138 |
|
|---|
| 139 | Example values: VBE_DISPI_ID0
|
|---|
| 140 |
|
|---|
| 141 | * VBE_DISPI_INDEX_XRES : WORD {R,W}
|
|---|
| 142 | This parameter can be used to read/write the vbe display X resolution (in pixels).
|
|---|
| 143 | It's illegal to set the XRES when the VBE is enabled (display code should generate PANIC).
|
|---|
| 144 |
|
|---|
| 145 | If the value written exceeds VBE_DISPI_MAX_XRES, the display code needs to generate a PANIC.
|
|---|
| 146 |
|
|---|
| 147 | Example values: 320,640,800,1024
|
|---|
| 148 |
|
|---|
| 149 | * VBE_DISPI_INDEX_YRES : WORD {R,W}
|
|---|
| 150 | This parameter can be used to read/write the vbe display Y resolution (in pixels).
|
|---|
| 151 | It's illegal to set the YRES when the VBE is enabled (display code should generate PANIC).
|
|---|
| 152 |
|
|---|
| 153 | If the value written exceeds VBE_DISPI_MAX_YRES, the display code needs to generate a PANIC.
|
|---|
| 154 |
|
|---|
| 155 | Example values: 200,400,480,600,768
|
|---|
| 156 |
|
|---|
| 157 | * VBE_DISPI_INDEX_BPP : WORD {R,W}
|
|---|
| 158 | This parameter can be used to read/write the vbe display BPP.
|
|---|
| 159 | It's illegal to set the BPP when the VBE is enabled (display code should generate PANIC).
|
|---|
| 160 |
|
|---|
| 161 | If the value written is an incompatible BPP, the display code needs to generate a PANIC.
|
|---|
| 162 |
|
|---|
| 163 | Example values: VBE_DISPI_BPP_8
|
|---|
| 164 |
|
|---|
| 165 | * VBE_DISPI_INDEX_ENABLE : WORD {R,W}
|
|---|
| 166 | This parameter can be used to read/write the vbe ENABLED state.
|
|---|
| 167 | If the bios writes VBE_DISPI_ENABLED then the display code will setup a hostside display mode
|
|---|
| 168 | with the current XRES, YRES and BPP settings.
|
|---|
| 169 | If the bios write VBE_DISPI_DISABLED then the display code will switch back to normal vga mode behaviour.
|
|---|
| 170 |
|
|---|
| 171 | Example values: VBE_DISPI_ENABLED, VBE_DISPI_DISABLED
|
|---|
| 172 |
|
|---|
| 173 | * VBE_DISPI_INDEX_BANK : WORD {R,W}
|
|---|
| 174 | This parameter can be used to read/write the current selected BANK (at 0xA0000).
|
|---|
| 175 | This can be used for switching banks in banked mode.
|
|---|
| 176 |
|
|---|
| 177 | [0xb0c1]
|
|---|
| 178 | * VBE_DISPI_INDEX_VIRT_WIDTH : WORD {R,W}
|
|---|
| 179 | This parameter can be used to read/write the current virtual width.
|
|---|
| 180 | Upon enabling a mode, this will be set to the current xres
|
|---|
| 181 | Setting this field during enabled mode will result in the virtual width to be changed.
|
|---|
| 182 | Value will be adjusted if current setting is not possible.
|
|---|
| 183 |
|
|---|
| 184 | * VBE_DISPI_INDEX_VIRT_HEIGHT : WORD {R}
|
|---|
| 185 | This parameter can be read in order to obtain the current virtual height.
|
|---|
| 186 | This setting will be adjusted after setting a virtual width in order to stay within limit of video memory.
|
|---|
| 187 |
|
|---|
| 188 | * VBE_DISPI_INDEX_X_OFFSET : WORD {R,W}
|
|---|
| 189 | The current X offset (in pixels!) of the visible screen part.
|
|---|
| 190 | Writing a new offset will also result in a complete screen refresh.
|
|---|
| 191 |
|
|---|
| 192 | * VBE_DISPI_INDEX_Y_OFFSET : WORD {R,W}
|
|---|
| 193 | The current Y offset (in pixels!) of the visible screen part.
|
|---|
| 194 | Writing a new offset will also result in a complete screen refresh.
|
|---|
| 195 |
|
|---|
| 196 |
|
|---|
| 197 | [0xb0c2]
|
|---|
| 198 | * VBE_DISPI_INDEX_BPP : WORD {R,W}
|
|---|
| 199 | The value written is now the number of bits per pixel. A value of 0 is treated
|
|---|
| 200 | the same as 8 for backward compatibilty. These values are supported: 8, 15,
|
|---|
| 201 | 16, 24 and 32. The value of 4 is not yet handled in the VBE code.
|
|---|
| 202 | * VBE_DISPI_INDEX_ENABLE : WORD {R,W}
|
|---|
| 203 | The new flag VBE_DISPI_NOCLEARMEM allows to preserve the VBE video memory.
|
|---|
| 204 | The new flag VBE_DISPI_LFB_ENABLED indicates the usage of the LFB.
|
|---|
| 205 |
|
|---|
| 206 | [0xb0c3]
|
|---|
| 207 | * VBE_DISPI_INDEX_ENABLE : WORD {R,W}
|
|---|
| 208 | If the new flag VBE_DISPI_GETCAPS is enabled, the xres, yres and bpp registers
|
|---|
| 209 | return the gui capabilities.
|
|---|
| 210 | The new flag VBE_DISPI_8BIT_DAC switches the DAC to 8 bit mode.
|
|---|
| 211 |
|
|---|
| 212 | [0xb0c4]
|
|---|
| 213 | * VBE_DISPI_TOTAL_VIDEO_MEMORY_MB set to 8 (moved to auto-generated vbetables.h)
|
|---|
| 214 |
|
|---|
| 215 | Displaying GFX (banked mode)
|
|---|
| 216 | --------------
|
|---|
| 217 | What happens is that the total screen is devided in banks of 'VBE_DISPI_BANK_SIZE_KB' KiloByte in size.
|
|---|
| 218 | If you want to set a pixel you can calculate its bank by doing:
|
|---|
| 219 |
|
|---|
| 220 | offset = pixel_x + pixel_y * resolution_x;
|
|---|
| 221 | bank = offset / 64 Kb (rounded 1.9999 -> 1)
|
|---|
| 222 |
|
|---|
| 223 | bank_pixel_pos = offset - bank * 64Kb
|
|---|
| 224 |
|
|---|
| 225 | Now you can set the current bank and put the pixel at VBE_DISPI_BANK_ADDRESS + bank_pixel_pos
|
|---|
| 226 |
|
|---|
| 227 | Displaying GFX (linear frame buffer mode)
|
|---|
| 228 | --------------
|
|---|
| 229 | NOT WRITTEN YET
|
|---|
| 230 |
|
|---|
| 231 | Notes
|
|---|
| 232 | -----
|
|---|
| 233 | * Since the XRES/YRES/BPP may not be written when VBE is enabled, if you want to switch from one VBE mode
|
|---|
| 234 | to another, you will need to disable VBE first.
|
|---|
| 235 |
|
|---|
| 236 | * Note when the bios doesn't find a valid DISPI_ID, it can disable the VBE functions. This allows people to
|
|---|
| 237 | use the same bios for both vbe enabled and disabled bochs executables.
|
|---|
