Why was kmod-spi-gpio-custom discontinued

crispyoz

Does anyone know why kmod-spi-gpio-custom was discontinued? I can't find any details in the sources but I have a recollection it related to a kernel change. I need full duplex spi and I'm better at software than hardware so I'm thinking about whether it's worth trying to revive it.

luz

I guess because the kernel changes are such that this is not very easy to do. I remember looking into it, finding some attempts from others trying without success, and then decided going the DTS overlay route was much more future proof (and enables not just what the few *-custom could do, but any standard driver).

Since then, I use software SPI as described in this post.

But I realize that by now it also comes pre-packaged and documented in the onion docs

Lazar Demin

@crispyoz I don't remember the exact reasoning, but in one kernel release all of the bitbang implementations of hw buses were taken out.
I really liked how flexible these modules were - you could specify which GPIOs did what in the insmod command that loaded the kernel module.

Like @luz mentioned, DT overlays are the best game in town for this at the moment.
We have the onion-dt-overlay-sw-spi package available, and we also recently put out a onion-dt-overlay-sw-spi-alt package that uses more readily accessible GPIOs:

sck -> gpio3
cs0 -> gpio2
mosi -> gpio1
miso -> gpio0

~~(coming soon to the documentation)~~ See the Software SPI bus article in the new documentation for more details.

It's not as easy as using kmod-spi-gpio-custom , but if you're comfortable using the OnionIoT/openwrt-sdk-wrapper, you can work off onion-dt-overlay-sw-spi to spin your own software spi package that uses GPIOs that work for you!

crispyoz

Thanks @Lazar-Demin and @luz . I'll look at the swd-spi overlay to see if it works for me, I need it on owrt 24.10 so hopefully it works there.

I'm not quite there with wrapper(s) yet, I agree they are great for standardisation but owrt 24.10 stable is already released and since rc5 performs well so I'm trying to keep more current.

Lazar Demin

@crispyoz DT overlay packages unfortunately won't work in vanilla 24.10

DT overlay depends on a few patches to the kernel that we add to the build system (See patches 251-253 at https://github.com/OnionIoT/openwrt-buildsystem-wrapper/tree/openwrt-23.05/onion/patches)

crispyoz

Thanks @Lazar-Demin saved me some work.