On Tue, 2020-11-10 at 15:40 +0100, Bartosz Golaszewski wrote:

On Tue, Nov 10, 2020 at 3:31 PM Linus Walleij [off-list ref] wrote:

quoted

On Fri, Nov 6, 2020 at 12:27 PM Damien Le Moal [off-list ref] wrote:

quoted

It may not be the best interface for regular end users to
manipulate gpios, but it is definitely super useful for developers to do quick
tests of their setup/drivers (which is what I did for my work with the Kendryte
K210 RISC-V SoC support).

It is a bit discouraging that RISC-V, which was invented after we already
obsoleted the sysfs ABI, is deploying this for development and test.

We need to think about a similar facility for users which is less
damaging but fulfils the same needs. I think I saw something a while
back that looked promising and added some funky files in debugfs
in a hierarchical manner per-gpiochip instead. That is how debugfs
should be used.

Basically something like what gpio-mockup does for events? Was it
something out-of-tree or was it on the mailing list?

Also: quick tests have the tendency to become long-term solutions. :)

Is gpioget/gpioset duo difficult/cumbersome to use? It's a serious
question - I wrote it in a way that was as user-friendly as possible
but maybe I'm missing something about sysfs that makes users prefer it
over a command-line tool. To me sysfs was always a PITA with the
global numbers etc. but it still seems to stick with others.

In my particular case, I am using a simple busybox userspace that has nothing
else but a shell, so I did not have the gpioget/gpioset tools. And to be frank,
I did not even know what tool to use to control GPIOs. It is the first time I
am touching GPIOs with Linux and did not spent time to study what should be
used once I saw that sysfs allowed controlling the pins for tests.

Removing sysfs entirely would likely force people to look for these tools to do
tests, and I really am an example here :)

I am using buildroot to generate the toolchain and busybox userspace for the
board.  I now see that libgpiod and gpio tools packages are in there but for
whatever reasons, I cannot select them for my RISC-V build. Will need to
explore why.


-- 
Damien Le Moal
Western Digital