The I2C transfer chain was stubbed end-to-end:
- i2cd's transfer path returned 'not implemented yet' for every
transfer, and its wire format didn't match the only in-tree consumer
(i2c-hidd sends a bare I2cTransferRequest, i2cd expected
I2cControlRequest::Transfer).
- intel-lpss-i2cd / dw-acpi-i2cd / amd-mp2-i2cd registered an adapter
name and parked forever without initializing the controller or
executing a transfer.
- intel-lpss-i2cd matched only legacy ACPI HIDs, which do not exist on
Meteor Lake / Arrow Lake platforms (LPSS I2C binds by PCI ID there,
per Linux drivers/mfd/intel-lpss-pci.c).
Replace with real implementations:
- New shared crate drivers/i2c/designware (dw-i2c): DesignWare I2C
master engine ported from Linux 7.1 i2c-designware-master.c and
i2c-designware-common.c — IC_CON + SCL timing computed from ic_clk
with Linux's exact hcnt/lcnt formulas (bxt_i2c_info 133 MHz for
LPSS, 100 MHz for ACPI-designated blocks), SDA hold with RX-hold
workaround, polling transfer engine with RESTART/STOP sequencing,
TX_ABRT decode (Nack/arbitration-lost/abort/timeout), 7/10-bit
addressing, bounded timeouts. Also provides the shared
/scheme/<name> transfer endpoint with register-then-ready ordering.
- intel-lpss-i2cd: PCI discovery for ARL-H (0x7750/0x7751,
0x7778-0x777b) and MTL-P (0x7e50/0x7e51, 0x7e78-0x7e7b) with 32/64-bit
BAR0 decode, ACPI alias resolution via FixedMemory32 == BAR0 across
/scheme/acpi/resources, legacy ACPI-HID path kept, i2cd registration
with bounded retry, serves /scheme/i2c-lpss.
- dw-acpi-i2cd: converted from register-and-park to the shared engine,
serves /scheme/dw-acpi-i2c.
- i2cd: real transfer routing — adapter resolution by name/alias
(exact, normalized, last-component) and forwarding to the provider
daemon's /scheme/<provider>/transfer endpoint.
- i2c-interface: I2cAdapterInfo gains provider_scheme + aliases
(serde-default, wire-compatible).
Tests: dw-i2c 3, intel-lpss-i2cd 3; full workspace cargo check clean;
base cooks for x86_64-unknown-redox.
Refs: local/docs/LG-GRAM-16Z90TP-COMPATIBILITY-PLAN.md Phase 4
Red Bear OS
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