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Diffstat (limited to 'vds.h')
| -rw-r--r-- | vds.h | 125 |
1 files changed, 125 insertions, 0 deletions
@@ -0,0 +1,125 @@ +/* + * VBMouse - Interface to the Virtual DMA Service (VDS) + * Copyright (C) 2022 Javier S. Pedro + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2 + * of the License, or (at your option) any later version. + + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + */ + +#ifndef VDS_H +#define VDS_H + +#include <stdbool.h> +#include <stdint.h> + +typedef unsigned char vdserr; +enum { + VDS_SUCCESSFUL = 0, + VDS_REGION_NOT_CONTIGUOUS = 1, + VDS_REGION_NOT_ALIGNED = 2, + VDS_UNABLE_TO_LOCK = 3, + VDS_NO_BUFFER_AVAIL = 4, + VDS_REGION_TOO_LARGE = 5, + VDS_BUFFER_IN_USE = 6, + VDS_INVALID_REGION = 7, + VDS_REGION_NOT_LOCKED = 8, + VDS_TOO_MANY_PAGES = 9, + VDS_INVALID_BUFFER_ID = 0xA, + VDS_BUFFER_BOUNDARY = 0xB, + VDS_INVALID_DMA_CHANNEL = 0xC, + VDS_DISABLE_COUNT_OVRFLOW = 0xD, + VDS_DISABLE_COUNT_UNDFLOW = 0xE, + VDS_NOT_SUPPORTED = 0xF, + VDS_FLAGS_NOT_SUPPORTED = 0x10, +}; + +enum { +/* + Bit 1 = Automatically copy to/from buffer + Bit 2 = Disable automatic buffer allocation + Bit 3 = Disable automatic remap feature + Bit 4 = Region must not cross 64K physical alignment boundary + Bit 5 = Region must not cross 128K physical alignment boundary + Bit 6 = Copy page-table for scatter/gather remap + Bit 7 = Allow non-present pages for scatter/gather remap +*/ + VDS_AUTO_COPY_DATA = 1 << 1, + VDS_NO_AUTO_ALLOC = 1 << 2, + VDS_NO_AUTO_REMAP = 1 << 3, + VDS_ALIGN_64K = 1 << 4, + VDS_ALIGN_128K = 1 << 5 +}; + +/** DMA Descriptor structure. Describes a potentially DMA-lockable buffer. */ +typedef _Packed struct VDS_DDS +{ + /** Size of this buffer. */ + uint32_t regionSize; + /** Logical/segmented address of this buffer, offset part */ + uint32_t offset; + /** Segment of this buffer. */ + uint16_t segOrSelector; + /** Internal VDS buffer ID. */ + uint16_t bufferId; + /** Physical address of this buffer. */ + uint32_t physicalAddress; +} VDS_DDS; + +static bool vds_available(void); +#pragma aux vds_available = \ + "mov ax, 0x40" \ + "mov es, ax" \ + "mov al, es:[0x7B]" \ + "and al, 0x20" \ + "setnz al" \ + __value [al] \ + __modify [ax es] + +/** Locks an already allocated buffer into a physical memory location. + * regionSize, offset and segment must be valid in the DDS, + * while the physical address is returned. */ +static vdserr vds_lock_dma_buffer_region(VDS_DDS __far * dds, unsigned char flags); +#pragma aux vds_lock_dma_buffer_region = \ + "stc" /* If nothing happens, assume failure. */ \ + "mov ax, 0x8103" \ + "int 0x4B" \ + "jc fail" \ + "mov ah, 0" \ + "jmp end" \ + "fail: test ah, ah" \ + "jnz end" \ + "mov ah, 0xFF" /* Force a error code if there was none. */ \ + "end:" \ + __parm [es di] [dx] \ + __value [ah] \ + __modify [ax] + +/** Unlocks a locked buffer. */ +static vdserr vds_unlock_dma_buffer_region(VDS_DDS __far * dds, unsigned char flags); +#pragma aux vds_unlock_dma_buffer_region = \ + "stc" \ + "mov ax, 0x8104" \ + "int 0x4B" \ + "jc fail" \ + "mov ah, 0" \ + "jmp end" \ + "fail: test ah, ah" \ + "jnz end" \ + "mov ah, 0xFF" \ + "end:" \ + __parm [es di] [dx] \ + __value [ah] \ + __modify [ax] + +#endif |