feat(drivers): bitfield register structs for 8237 DMA + FDC DOR#434
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Adds typed bitfield-struct definitions for the 8237A single-channel
mask register (port 0x0A / 0xD4), the 8237A mode register
(port 0x0B / 0xD6), and the 82077AA floppy digital output register
(port 0x3F2) to src/include/registers.h.
fdc and sb16 — the only drivers that touch the shared DMA
controller — replace every magic-byte kernel_outb on those ports
with named-field literals:
struct dma_mode m = { .channel = 1, .transfer = 2,
.autoinit = 1, .mode = 1 };
kernel_outb(0x0B, *(uint8_t *)&m);
fdc_init's DOR reset sequence now uses struct fdc_dor literals
instead of the bare 0 / 0x0C bytes, and fdc_read_sector /
fdc_write_sector construct dma_mode locals at the call site (0x46
for floppy-read, 0x4A for floppy-write). sb16_open / sb16_close
drop the multi-line bit-table comment that documented 0x59 — every
field now reads as its datasheet name.
Each designated init folds to a single ``mov byte [ebp-K], <const>``
via the bitfield const-fold peepholes from the previous release, so
there's no codegen regression versus the magic-byte form.
Tests:
- tests/test_bboefs.py (exercises fdc_read_sector / fdc_write_sector
end-to-end through bbfs)
- tests/test_asm.py (full boot path including fdc_init's DOR reset)
- tests/test_programs.py
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Summary
struct dma_mask,struct dma_mode, andstruct fdc_dortosrc/include/registers.hcovering the 8237A single-channel mask (port 0x0A/0xD4), the 8237A mode register (port 0x0B/0xD6), and the 82077AA floppy digital output register (port 0x3F2).kernel_outbinfdc.candsb16.cthat touches those ports — DMA channel mask/unmask, channel mode bytes (0x46 / 0x4A for floppy, 0x59 for audio), and the FDC reset DOR sequence — to designated-init struct literals with datasheet field names. Each literal still folds to a singlemov byte [ebp-K], <const>via the existing bitfield-collapse peephole.Test plan
tests/test_bboefs.py(exercisesfdc_read_sector/fdc_write_sectorend-to-end via bbfs)tests/test_asm.py(full boot path includingfdc_init's DOR reset)tests/test_programs.py🤖 Generated with Claude Code