Re: rtw88, rtw89 -- options for bringing a couple rtw standalone GitHub repos into backports.git

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Hi Brian,

> lwfinger/rtw89 is an out-of-tree backport of the in-tree rtw89. outside
> of documentation, files needed to build/manage the driver, and inserted
> #if #else #endif statements for compatibility. It attempts to be a
> "copy" of the upstream rtw89. there is no new hardware support or
> capabilities built into it as far as I understand.
> The purpose of this repo shares the same stated goal of Linux Backports
> which is "taking code from newer Linux kernel versions and adapting
> them so they can be compiled and run on older kernel versions."

Right, OK.

> Right now, the main way Larry does this is by filtering new rtw89
> patches out of `wireless-next` and then incrementally applying them
> via a git workflow using quilt and wiggle while applying #if #else
> #endif for the changes between versions.


> What I am trying to achieve:
> 1. Compatibility that reaches back further. Right now lwfinger/rtw89
> repo only extends back to kernel version 5.7.

We did keep pushing the cut-off for backports, but I think it's at
4.something now? Also, some drivers have a higher cut-off, per the
'dependencies' file. The only RTL thing I see mentioned though is
RTL8723BS with 5.4.

> Ok, I need test this properly with rtw89 and a few different older
> kernels. There were a few things that were unclear to me about how
> backports works that are now more clear.
> When I check for the rtw89 cards, I see:
>      $ pwd
>      /home/user/backports/backport/defconfigs
>      $ cat check_for_rtw89_cards.awk
>      BEGIN { found = 0 } # print line
>      if found /8852AE|8851BE|8852BE|8852CE/ {
>          print $0 found = 1 exit
>      } END { if (found == 0) { print "not found" } }
>      $ awk -f check_for_rtw89_cards.awk rtlwifi
>      not found

Well not having anything in the defconfig doesn't mean much - we used to
at least try to build _all_ drivers that were possible (i.e. where
dependencies could be satisfied), and "allmodconfig" works here I think.

The copy-list takes all of the drivers under drivers/net/wireless/ (and
even some from staging), so it should be included.

> I will start looking into getting rtw89 running in backports.git if
> my tests show they are not yet supported.

Sure, please do try.

Also if you run into any missing backports let us know - there currently
aren't any not applied yet [1] and there are almost certainly some
integrated into iwlwifi [2] not sent as backports.git patches yet.


> Otherwise, alot of my understanding of how backports work was not
> completely wrong and you made some important clarifications re:
> usage and options that are available re: commit history.
> So as far as how I can decide what I will do with the lwfinger/rtw89
> repo and others like it entails figuring out the current state of
> these drivers within the Linux backports project and how that can
> fit in with our current users and how we support them.

Makes sense.

> Initially, I was just committed to putting in the work on these drivers
> in their standalone GitHub repos, but it seems like consolidating
> those efforts seems like the best approach if I can make it work. 

Yeah, there's probably no good reason to have a repo per driver, doing
effectively the same thing more than once.

> Ok, I am going to start actually running backports against different
> setups to see what I can get a handle on and then follow-up
> accordingly.


> If there is anything specific to look into, let me know.

Don't think so.

To get a better feel for how backports works and what all the
transformations look like etc., you can run gentree with --git-debug
command line, then it creates a git tree in the output and tracks there
individual *changes* it makes, for debug. Not to be confused with
tracking the input commits, of course, that's git-tracker's job.

If you do decide to use git-tracker, let me know, I'll check if we have
some additional changes internally to how it handles merges etc. We

Have fun exploring! :-)
And do let us know if you hit any snags.

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