nv-fermi-drv

An independent out-of-tree Linux kernel module (DRM/KMS) for NVIDIA Fermi-architecture GPUs, specifically the GeForce GT 430 (GF108 chip).

Goal

Full support for NVIDIA Fermi cards on modern Linux kernels (6.x+), fixing key power-management (reclocking) gaps that remain unaddressed in the existing nouveau driver for this generation of hardware.

Design principles

• Isolation from nouveau. The driver is written as a standalone module built on the standard Linux Kernel DRM API, not as a fork of the nouveau codebase.
• Reference-only approach. The nouveau and envytools codebases are used strictly as a specification and reference for MMIO registers, VBIOS table structures, and the I2C bus algorithms. No code is copied directly.
• Portability. The build is based on DKMS, ensuring the driver is portable across distributions (Arch, Ubuntu, Mint, Fedora).

Target hardware

Parameter	Value
Card	GeForce GT 430
Chip	GF108 (Fermi)
Vendor ID	0x10de
Device ID	0x0de1

Source layout

• nv_fermi_drv.h -- shared macros, register defines, data structures (nv_fermi_priv, nv_dcb_header), function prototypes.
• core.c -- module init/exit, PCI driver registration, probe/remove.
• vbios.c -- VBIOS parsing: expansion ROM read, BIT table, DCB table.
• i2c.c -- GPIO/I2C engine (in progress).
• Makefile -- Kbuild build file, links core.o vbios.o i2c.o into nv_fermi_drv.ko.

Current status

The project is currently in Phase 3 (see the table below).

Phase 1 -- project skeleton and hardware detection (complete)

• Repository structure and Makefile for building on Arch Linux.
• PCI ID registration for the device (10de:0de1).
• Module load/unload functions with dmesg logging.
• Confirmed device takeover from the stock kernel driver.

Phase 2 -- card memory access: MMIO and BAR (complete)

• Device activation via pci_enable_device().
• Region reservation via pci_request_regions().
• Mapping of BAR0 (registers) and BAR1 (video memory) via pci_ioremap_bar().
• Basic register read/write macros (ioread32/iowrite32).
• Reading and decoding NV_PMC_BOOT_0, confirming the chipset ID (0xC1 = GF108).

Phase 3 -- VBIOS parser: complete. I2C/SMBus engine: not started.

VBIOS parsing (complete, verified on real hardware):

• VBIOS location and read via pci_map_rom(), with option ROM signature validation.
• BIT (BIOS Information Table) parser: signature search, header parsing, enumeration of all subsystem tokens, header checksum check.
• DCB (Device Configuration Table) location: tries the BIT token i first, falls back to the legacy pointer at 0x36, and picks whichever candidate produces a plausible DCB header (on this hardware, the BIT i pointer turned out to be wrong -- the legacy pointer is the one that works).
• DCB header parsing (version, header size, entry count and size), plus DCB entry table hex-dump.
• I2C table offset confirmed at DCB header+0x04 (verified against real table content, not just header shape).
• GPIO table offset confirmed at DCB header+0x0a (verified against real table content -- the header+0x06 field, which some references suggest, turned out to point at executable code on this VBIOS, not a table).

Not yet done (this is the part still open):

• Decoding the individual I2C and GPIO table entries (bitfields for line/function/address).
• I2C/SMBus engine initialization in i2c.c -- currently a stub that logs and returns.

Phase 4 -- power and clock management (reclocking) (not started)

Extracting PSTATE performance profiles, writing a PWM voltage-control driver, PLL clock control code, a basic in-kernel power-management daemon.

Phase 5 -- graphics output and Mesa Gallium3D (not started)

DRM/KMS subsystem integration for display init and video output management, GEM/TTM memory manager for framebuffer allocation, a minimal userspace Mesa Gallium3D state tracker.

Building

Requires the headers for your currently running kernel to be installed.

git clone https://github.com/eco1kd/NovaFermi.git
cd nv-fermi-drv
make

Loading the module

sudo make load

If the card is already claimed by the stock driver (nouveau), unbind it first:

echo "0000:XX:00.0" | sudo tee /sys/bus/pci/drivers/nouveau/unbind
echo "0000:XX:00.0" | sudo tee /sys/bus/pci/drivers/nv_fermi_drv/bind

Find the device's bus address with lspci -nn | grep 10de.

Viewing logs

sudo make log

or directly:

sudo dmesg -w | grep nv_fermi_drv

Unloading the module

sudo make unload

Warning

This project is at an early development stage and works with undocumented NVIDIA hardware via direct MMIO and VBIOS access. The current phases (1-3) are limited to read operations and do not change the card's power or clock state. Starting with Phase 4, the driver will write to registers controlling voltage and frequency -- use at that stage will come with additional warnings and safety guards.

License

GPL-2.0