comprehensive list of deprecated kernel features?

[xgivolari]

Hello everyone,

I am looking for information on which options, features, subsystems, etc.. are not in active development anymore and can be left out. For example, according to the Fedora 36 change notes, the entire framebuffer subsystem is deprecated. All fbdev drivers can be disabled and are replaced by CONFIG_DRM_SIMPLEDRM. The only reason for keeping the subsystem itself is for fbcon support. Where can I find out which other parts of the kernel are deprecated? Thank you!

[psycho]

Hi Xgivolari.

CONFIG_DRM_SIMPLEDRM has never worked for me: perhaps not surprisingly (given that the nvidia-driver messages say explicitly that it shouldn't be set), on my hardware it stops my nvidia kernel module from loading (so I use good old VESA for a high resolution console). Plenty of deprecated features are still useful or even necessary in some situations: just because the developers have flagged something as unlikely to be around in future doesn't mean you should definitely stop using it immediately. I imagine if you went through your kernel systematically disabling every deprecated feature you might give yourself some unnecessary headaches: it makes more sense to assess everything on a case-by-case basis, depending on what it is and whether the replacement's really a better solution for you.

The kernel source is quite well documented: generally speaking if you're selecting a deprecated feature via make menuconfig it will tell you (and even advise you re what to do instead)...so you probably don't need any additional documents (your custom kernel will already be informed by the guidance in the config menus themselves). If you're wanting a comprehensive list, all together in one place, I guess you could grep the source tree and make your own...but it sounds like you're assuming if something "is not in active development" (or at least is "deprecated") then it "can be left out"...but that's not the case. If it were that simple they'd just remove the features rather than leaving them in and flagging them as deprecated: they're still there because some people still use them, so you're probably better off just factoring it in as something to consider ("do I really want to keep using this deprecated feature or can I switch to the new alternative?") rather than aiming to identify and purge every bit of deprecated code.

To sum up, I don't know of any comprehensive up-to-date list of all deprecated kernel features, but I'm guessing nobody maintains one because it's not really necessary (deprecated code often works perfectly well...sometimes better, for some people, than the new code...your example of CONFIG_DRM_SIMPLEDRM being a good one, as Fedora's advice there just breaks my systems).

[Goverp]