Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the nvfd utility by introducing per-GPU fan mode switching capabilities via the command-line interface. This allows for granular control over individual NVIDIA GPU fan behavior, enabling users to select between driver-controlled 'auto' mode, a custom 'curve' mode, or a fixed 'manual' speed. The changes also include a practical example script that showcases how this new functionality can be used to implement an intelligent, temperature-aware fan control system, ultimately improving acoustic comfort during periods of low GPU activity.

Highlights

• Enhanced CLI for Per-GPU Fan Control: New command-line interface options have been added to nvfd, allowing users to set individual GPUs to 'auto', 'curve', or 'manual' fan modes directly from the CLI.
• Dynamic Fan Mode Switching Script Example: An example bash script (nvfd-fan-control.sh) is provided, demonstrating how to leverage the new CLI features to automatically switch GPU fan modes between 'auto' and 'curve' based on temperature thresholds, aiming for quieter operation during low GPU utilization.

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Thanks for the contribution and the detailed explanation!

I'll review the PR and test it on my setup tomorrow morning and get back to you with feedback.

@ricky-chaoju Thank you for the review, I'm going to check this later today

@ricky-chaoju It got quite big from where it started, I took the freedom to add a new root folder : utils, to store the script and systemd unit, which can be optionally installed.

The main.c code is much cleaner now, based on your review.

The original description were updated to reflect actual state of this PR.

@ricky-chaoju : I've processed your pertinent remarks, and have a few ones :

• I see a small problem : we don't keep track of an utils installation, so a user (that would not have RTFM) could uninstall but keep utils unit that would then fail at least until next boot where the After=nvfd.service hook would never trigger.
• The config.json (or a new utils.json) could track installed utils to automatically remove them when main uninstall is called. It makes sense to uninstall only utils, but none to uninstall main and keep utils.
• This may be out of scope for this PR

Thanks for addressing all the previous review items — the code is much cleaner now.

A few remaining nits before we merge:

1. Duplicate .PHONY in Makefile — There are two .PHONY lines (the new one and the original). Please merge them into one.

2. nvfd-fan-control.service missing trailing newline — The file doesn't end with a newline character.

3. argc == 4 error message is misleading — Running nvfd 99 manual 50 (invalid GPU index) prints "Invalid command: manual", but manual is valid — it's the GPU index that's wrong. Please split the checks:

   } else if (argc == 4) {
       int gpu_idx = atoi(argv[1]);
       if (strcmp(argv[2], "manual") != 0) {
           printf("Invalid command: %s\n", argv[2]);
           // ...
       } else if (gpu_idx < 0 || gpu_idx >= (int)device_count) {
           printf("Invalid GPU index. Use 'nvfd list' to see available GPUs.\n");
           // ...
       } else {
           speed = atoi(argv[3]);
           gpu_index = gpu_idx;
       }
   }

4. README.zh-TW.md has simplified Chinese — "二进制文件" should be "二進位檔案".

Regarding the utils uninstall tracking issue you raised — good catch, I agree that uninstalling main while keeping utils makes no sense and would leave a broken service. Let's handle that in a follow-up issue to keep this PR focused.

LGTM! Thanks for the fix.