hid: tmff2: add Thrustmaster T500RS wheel base driver

[cazzoo]

This driver has been built from scratch based the previous dirty driver (see #175) and on captures from ffbsdl tool ran in windows for all possible effects (through SDL2 library).

[cazzoo]

Hi @Kimplul ,

Here is a new version of the driver, fully rebuilt from scratch. I've been trying to do my best to get it done the right way, steering its content the best I could (with my knowledge). I'll discard the previous PR that is not optimal. This one should be supporting more effects, and should be better designed. I've been also working on documentation to make it more comprehensive and based on SDL2 real examples.

Again, I am fully open to your feedback (and also @MmAaXx500 ones) that were really valuable by the other PR, so when you will have time, I'd really happy to get to your review.

Thanks

[Kimplul]

Thanks for continuing on this project, I was getting worried that we scared you off :)

I did a quick overview. The documentation in particular looks a lot better, having clear examples of what each packet does and how they build up to a full effect upload helped greatly. I haven't done any cross-referencing between the docs and implementation, as I still found quite a lot of smaller issues I'd like taken care of first. I'll do a more thorough review after that.

Not entirely sure what you mean by 'from scratch', for instance the comment explaining the set_gain rationale is identical between this and the previous PR.

[cazzoo]

Got the code and the PR updated based on all your feedback. All were valid, the only ones I haven't worked on are the SQUARE effect I plan to work on later and the git version (that I can easily remove).
Let me know any other findings or your thoughts on this updated code

[cazzoo]

Hi @Kimplul ,

I've been working again on the PR, responding to all your points (almost all -- if not all -- were relevant), and introducing some missing features (FF_SQUARE missing and 0x05 conditional effect that was incorrectly done). If you mind having another pass, I'd be really happy.
Thanks

[Kimplul]

Sorry about the delay, bit busy before the end of the year. I had a look through the resolved comments, most looked good but there were a few that I decided to unresolve, please have a second look at them.

I still haven't cross-referenced documentation to the code, I'll try and get that done by the end of next week, but based on a cursory look the code looks a lot better now. Seems you managed to shave off ~400 lines of code, well done.

Please also add a copyright statement to the start of the files you created, something like https://elixir.bootlin.com/linux/v6.18.1/source/drivers/hid/hid-retrode.c for example. I really should do that as well to the bits I wrote, but this is the first 'major' new addition to the driver so I've never really had any reason to think about it before.

[cazzoo]

No worries, thank you for the feedback you provided. Take the necessary time for whatever need review. I am not in the hurry, and this driver does work for me already so It can last as long as necessary from your end.

I'm happy we trend to get somewhat a stable mergeable version.
I just pushed a new part of code that handled previously the mode switch (from boot/init to normal mode). This is the part where I have the least confidence. The logic is fully fine, it's working well, but I'm not sure at all on code quality and the compliance/integration with the base driver. If you may give a glance when you can, I'd be happy to send some more time if needed.

Cheers

[Kimplul]

I just pushed a new part of code that handled previously the mode switch (from boot/init to normal mode). This is the part where I have the least confidence.

That's the responsibility of hid-tminit, is it not working? Regardless, please revert and if needed, open up a separate PR in https://github.com/Kimplul/hid-tminit/tree/tspc.

[cazzoo]

I just pushed a new part of code that handled previously the mode switch (from boot/init to normal mode). This is the part where I have the least confidence.

That's the responsibility of hid-tminit, is it not working? Regardless, please revert and if needed, open up a separate PR in https://github.com/Kimplul/hid-tminit/tree/tspc.

It is indeed not working with the current code. I'll revert this. Not sure how I should update the init driver yet. Maybe just specifying the boot mode, will test.
Otherwise, if you have any idea based on my commit, let me know

---

EDIT: I just open a PR against hid-tminit for TSCP branch (even though it's t500rs code update): Kimplul/hid-tminit#2

I tested and it appears to work fine with that code and my driver (and the mode switch reverted from within the driver)

[Kimplul]

EDIT: I just open a PR against hid-tminit for TSCP branch (even though it's t500rs code update)

Yeah, I intended to merge tspc into usb as part of adding support for the TS-PC, but seems I forgot. I'll sort it out once we deal with this PR, don't want to start changing too many moving bits at the same time.

[cazzoo]

There we are @Kimplul , I've been addressing all the points I guess, and introduced some fix also here or there (you can check latest commits, small scoped). Take your time for the documentation cross-check and let me know, in parallel I'm trying to improve the bits where I can

[Kimplul]

Sorry about the delay, I've been busier than expected. I mainly focused on the docs and found some inaccuracies and points of improvement, please have a look at those.

I applied some style fixes myself, please cherry-pick them from https://github.com/Kimplul/hid-tmff2/tree/cazzoo-hardening/t500rs-driver. I don't have push access to your branch and opening a PR for a PR seemed a bit silly, but the changes were trivial enough that I didn't really want to request them explicitly. Kind of a clumsy part of the PR flow, but eh.

Regarding style, I've tried to follow the Linux Kernel style guide in this repo. Most significantly, it dictates a tab width of 8 spaces, whereas this has a width of 2, please fix that. You might also want to try running your code through clang-format with the kernel's style configuration, see https://www.kernel.org/doc/html/next/dev-tools/clang-format.html

[cazzoo]

Thank you @Kimplul for all the feedback. No worries for the delay, I also had a lot of parallel work to take care of in the meantime.
Your feedback were valuable, as usual, and it helped to find some odd things (fixed Saturation for instance) that I fixed I believe, making the driver more stable and robust.

Now I believe the code and much more ready, and the documentation updated appropriately and more accurately. Please have another pass and I'd be happy to change anything that's not fine by your POV.