Il giorno lun 20 gen 2025 alle ore 14:42 Caleb James DeLisle via
openwrt-devel <openwrt-devel@lists.openwrt.org> ha scritto:
The sender domain has a DMARC Reject/Quarantine policy which disallows
sending mailing list messages using the original "From" header.
To mitigate this problem, the original message has been wrapped
automatically by the mailing list software.
---------- Forwarded message ----------
From: Caleb James DeLisle <c...@cjdns.fr>
To: OpenWrt Development List <openwrt-devel@lists.openwrt.org>
Cc:
Bcc:
Date: Mon, 20 Jan 2025 14:41:15 +0100
Subject: Porting the EN75xx platform - code style questions.
Hello folks,
I'm back to my old time-waster, trying to port to an EN7526.
I'd like some advice on what is the "best" way to code this so that it's easily
merged, and not
excluded from upstreaming for quality reasons.
Well most of the time... Nothing hardcoded or minimal and every patch MUST pass
scripts/checkpatch.sh Anything in mach-* is a no no and everything should be
correctly supported in DT.
First question: I'm planning on pretty much rewriting everything from scratch,
so I'd like to know
what is the Gold Standard of MIPS platforms that I should be emulating. I'm
currently trying to
pattern off of the ralink platform in linux upstream, but I don't know if what
I'm copying is the best.
This really depends... Hope other can answer to this.
Second question: What's the appropriate balance between hard-coding the system
type, and trying to
detect and roll with whatever you have?
The appropriate balance is not hard-coding anything... As said,
support everything in DT well documented
make it modular.
At one extreme, I could make the build be for one SoC only, e.g. EN7526G, and
make it panic if it
boots on anything else (even like an EN7526C which would probably boot ok). At
the other extreme, I
could make the code use runtime detection only and let the user choose from a
menu of SoCs and have
them mutually exclude if they have major differences like byte order.
I feel both solution are not ok... Just make different subtarget if
they are different enough.
Or a big .dtsi and different device for each kind of board.
The 2nd direction makes a lot of sense to me because I can make it so you can
select Generic and
you'll get an OS which tries really hard to boot on whatever you put it on, but
if you select a
specific processor then some function like `static inline bool en75_soc_is(enum
en75_soc_type t)`
will be constant folded, so dead code elimination will clean up any if block
that references an
another SoC.
That kind of function are downstream SDK hacks and laziness... Again
correct DT compatible and
of_device_is_compatible should be the correct way.
The problem is device trees. These boards use an old trx loader so FIT is out
of the question, but
what I could do is append multiple DTs and have plat_mem_setup() just walk them
like a linked list
looking for the index of the identified SoC, but I wanted to ask for opinions
first before doing
something "smart" that might just lead to code nobody wants to go near.
Apply KIS (keep it simple) rule. We don't want massive generic
firmware that can boot on any
kind of router/SoC in the world. We want small image suited for the task.
With this in mind, we build one image for the SoC with the appended
appropriate DTS and be
done with it. No detection and selection of the DTS based on the
strange value detected at
runtime. What should be really understood is how different they are.
If they are GT or E variant (with for example the fact that one board
have wifi chip and another
have an additional ethernet port) then these can be handled with
modular .dtsi and the final
device will include the related dtsi.
If they are different CPU, most of the time it's a different subtarget
if they are different enough.
For the sake of CPU init for first stage, it's DT compatible way and a
switch case in mips march.
Third question: Anybody going to be at FOSDEM?
A big maybe for me.
Thanks,
Caleb
_______________________________________________
openwrt-devel mailing list
openwrt-devel@lists.openwrt.org
https://lists.openwrt.org/mailman/listinfo/openwrt-devel
