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diff --git a/vgabios/vbe_display_api.txt b/vgabios/vbe_display_api.txt new file mode 100644 index 0000000..fddb78b --- /dev/null +++ b/vgabios/vbe_display_api.txt @@ -0,0 +1,237 @@ +VBE Display API +------------------------------------------------------------------------------------------------------------- + This document is part of the Bochs/VBEBios documentation, + it specifies the bochs host <-> vbebios client communication. + + That means, the display code implementation and the vbebios code depend + very heavily on each other. As such, this documents needs be synchronised + between bochs CVS and the vgabios CVS. + + This document does not describe how the VBEBios implements the VBE2/3 spec. + This document does not describe how the Bochs display code will display gfx based upon this spec. + + +API History +----------- +0xb0c0 supports the following VBE_DISPI_ interfaces (present in Bochs 1.4): + VBE_DISPI_INDEX_ID + VBE_DISPI_INDEX_XRES + VBE_DISPI_INDEX_YRES + VBE_DISPI_INDEX_BPP + VBE_DISPI_INDEX_ENABLE + VBE_DISPI_INDEX_BANK + + Bpp format supported is: + VBE_DISPI_BPP_8 + +0xb0c1 supports 0xb0c0 VBE_DISPI_ interfaces, additional interfaces (present in Bochs 2.0): + VBE_DISPI_INDEX_VIRT_WIDTH + VBE_DISPI_INDEX_VIRT_HEIGHT + VBE_DISPI_INDEX_X_OFFSET + VBE_DISPI_INDEX_Y_OFFSET + +0xb0c2 supports 0xb0c1 VBE_DISPI_ interfaces, interfaces updated for + additional features (present in Bochs 2.1): + VBE_DISPI_INDEX_BPP supports >8bpp color depth (value = bits) + VBE_DISPI_INDEX_ENABLE supports new flags VBE_DISPI_NOCLEARMEM and VBE_DISPI_LFB_ENABLED + VBE i/o registers changed from 0xFF80/81 to 0x01CE/CF + +0xb0c3 supports 0xb0c2 VBE_DISPI_ interfaces, interfaces updated for + additional features: + VBE_DISPI_INDEX_ENABLE supports new flags VBE_DISPI_GETCAPS and VBE_DISPI_8BIT_DAC + +0xb0c4 VBE video memory increased to 8 MB + + +History +------- + Version 0.6 2002 Nov 23 Jeroen Janssen + - Added LFB support + - Added Virt width, height and x,y offset + + Version 0.5 2002 March 08 Jeroen Janssen + - Added documentation about panic behaviour / current limits of the data values. + - Changed BPP API (in order to include future (A)RGB formats) + - Initial version (based upon extended display text of the vbe bochs display patch) + + +Todo +---- + Version 0.6+ [random order] + - Add lots of different (A)RGB formats + +References +---------- + [VBE3] VBE 3 Specification at + http://www.vesa.org/vbe3.pdf + + [BOCHS] Bochs Open Source IA-32 Emulator at + http://bochs.sourceforge.net + + [VBEBIOS] VBE Bios for Bochs at + http://savannah.gnu.org/projects/vgabios/ + + [Screenshots] Screenshots of programs using the VBE Bios at + http://japj.org/projects/bochs_plex86/screenshots.html + +Abbreviations +------------- + VBE Vesa Bios Extension + DISPI (Bochs) Display Interface + BPP Bits Per Pixel + LFB Linear Frame Buffer + + +#defines +-------- +vbetables-gen.c + #define VBE_DISPI_TOTAL_VIDEO_MEMORY_MB 8 + +vbe.h + #define VBE_DISPI_BANK_ADDRESS 0xA0000 + #define VBE_DISPI_BANK_SIZE_KB 64 + + #define VBE_DISPI_MAX_XRES 1024 + #define VBE_DISPI_MAX_YRES 768 + + #define VBE_DISPI_IOPORT_INDEX 0x01CE + #define VBE_DISPI_IOPORT_DATA 0x01CF + + #define VBE_DISPI_INDEX_ID 0x0 + #define VBE_DISPI_INDEX_XRES 0x1 + #define VBE_DISPI_INDEX_YRES 0x2 + #define VBE_DISPI_INDEX_BPP 0x3 + #define VBE_DISPI_INDEX_ENABLE 0x4 + #define VBE_DISPI_INDEX_BANK 0x5 + #define VBE_DISPI_INDEX_VIRT_WIDTH 0x6 + #define VBE_DISPI_INDEX_VIRT_HEIGHT 0x7 + #define VBE_DISPI_INDEX_X_OFFSET 0x8 + #define VBE_DISPI_INDEX_Y_OFFSET 0x9 + + #define VBE_DISPI_ID0 0xB0C0 + #define VBE_DISPI_ID1 0xB0C1 + #define VBE_DISPI_ID2 0xB0C2 + #define VBE_DISPI_ID3 0xB0C3 + #define VBE_DISPI_ID4 0xB0C4 + + #define VBE_DISPI_DISABLED 0x00 + #define VBE_DISPI_ENABLED 0x01 + #define VBE_DISPI_VBE_ENABLED 0x40 + #define VBE_DISPI_NOCLEARMEM 0x80 + + #define VBE_DISPI_LFB_PHYSICAL_ADDRESS 0xE0000000 + +API +--- + The display api works by using a index (VBE_DISPI_IOPORT_INDEX) and + data (VBE_DISPI_IOPORT_DATA) ioport. One writes the index of the parameter to the index port. + Next, the parameter value can be read or written. + +[0xb0c0] + * VBE_DISPI_INDEX_ID : WORD {R,W} + This parameter can be used to detect the current display API (both bochs & vbebios). + The bios writes VBE_DISPI_ID0 to the dataport and reads it back again. + This way, the display code knows the vbebios 'ID' and the vbebios can check if the correct + display code is present. + As a result, a PANIC can be generated if an incompatible vbebios/display code combination is detected. + This panic can be generated from the bochs display code (NOT the bios, see Notes). + + Example values: VBE_DISPI_ID0 + + * VBE_DISPI_INDEX_XRES : WORD {R,W} + This parameter can be used to read/write the vbe display X resolution (in pixels). + It's illegal to set the XRES when the VBE is enabled (display code should generate PANIC). + + If the value written exceeds VBE_DISPI_MAX_XRES, the display code needs to generate a PANIC. + + Example values: 320,640,800,1024 + + * VBE_DISPI_INDEX_YRES : WORD {R,W} + This parameter can be used to read/write the vbe display Y resolution (in pixels). + It's illegal to set the YRES when the VBE is enabled (display code should generate PANIC). + + If the value written exceeds VBE_DISPI_MAX_YRES, the display code needs to generate a PANIC. + + Example values: 200,400,480,600,768 + + * VBE_DISPI_INDEX_BPP : WORD {R,W} + This parameter can be used to read/write the vbe display BPP. + It's illegal to set the BPP when the VBE is enabled (display code should generate PANIC). + + If the value written is an incompatible BPP, the display code needs to generate a PANIC. + + Example values: VBE_DISPI_BPP_8 + + * VBE_DISPI_INDEX_ENABLE : WORD {R,W} + This parameter can be used to read/write the vbe ENABLED state. + If the bios writes VBE_DISPI_ENABLED then the display code will setup a hostside display mode + with the current XRES, YRES and BPP settings. + If the bios write VBE_DISPI_DISABLED then the display code will switch back to normal vga mode behaviour. + + Example values: VBE_DISPI_ENABLED, VBE_DISPI_DISABLED + + * VBE_DISPI_INDEX_BANK : WORD {R,W} + This parameter can be used to read/write the current selected BANK (at 0xA0000). + This can be used for switching banks in banked mode. + +[0xb0c1] + * VBE_DISPI_INDEX_VIRT_WIDTH : WORD {R,W} + This parameter can be used to read/write the current virtual width. + Upon enabling a mode, this will be set to the current xres + Setting this field during enabled mode will result in the virtual width to be changed. + Value will be adjusted if current setting is not possible. + + * VBE_DISPI_INDEX_VIRT_HEIGHT : WORD {R} + This parameter can be read in order to obtain the current virtual height. + This setting will be adjusted after setting a virtual width in order to stay within limit of video memory. + + * VBE_DISPI_INDEX_X_OFFSET : WORD {R,W} + The current X offset (in pixels!) of the visible screen part. + Writing a new offset will also result in a complete screen refresh. + + * VBE_DISPI_INDEX_Y_OFFSET : WORD {R,W} + The current Y offset (in pixels!) of the visible screen part. + Writing a new offset will also result in a complete screen refresh. + + +[0xb0c2] + * VBE_DISPI_INDEX_BPP : WORD {R,W} + The value written is now the number of bits per pixel. A value of 0 is treated + the same as 8 for backward compatibilty. These values are supported: 8, 15, + 16, 24 and 32. The value of 4 is not yet handled in the VBE code. + * VBE_DISPI_INDEX_ENABLE : WORD {R,W} + The new flag VBE_DISPI_NOCLEARMEM allows to preserve the VBE video memory. + The new flag VBE_DISPI_LFB_ENABLED indicates the usage of the LFB. + +[0xb0c3] + * VBE_DISPI_INDEX_ENABLE : WORD {R,W} + If the new flag VBE_DISPI_GETCAPS is enabled, the xres, yres and bpp registers + return the gui capabilities. + The new flag VBE_DISPI_8BIT_DAC switches the DAC to 8 bit mode. + +[0xb0c4] + * VBE_DISPI_TOTAL_VIDEO_MEMORY_MB set to 8 (moved to auto-generated vbetables.h) + +Displaying GFX (banked mode) +-------------- + What happens is that the total screen is devided in banks of 'VBE_DISPI_BANK_SIZE_KB' KiloByte in size. + If you want to set a pixel you can calculate its bank by doing: + + offset = pixel_x + pixel_y * resolution_x; + bank = offset / 64 Kb (rounded 1.9999 -> 1) + + bank_pixel_pos = offset - bank * 64Kb + + Now you can set the current bank and put the pixel at VBE_DISPI_BANK_ADDRESS + bank_pixel_pos + +Displaying GFX (linear frame buffer mode) +-------------- + NOT WRITTEN YET + +Notes +----- + * Since the XRES/YRES/BPP may not be written when VBE is enabled, if you want to switch from one VBE mode + to another, you will need to disable VBE first. + + * Note when the bios doesn't find a valid DISPI_ID, it can disable the VBE functions. This allows people to + use the same bios for both vbe enabled and disabled bochs executables. |