Re: [PATCH] leds: Introduce userspace leds driver

[Jacek Anaszewski]

Hi Pavel,

On 09/15/2016 02:41 PM, Pavel Machek wrote:
> Hi!
>
> > Thanks for the patch. It is very nice. I have only one minor remark
> > in the code.
> >
> > I think that it would be good to add a documentation for this
> > driver to Documentation/leds, with exemplary C program instead
> > of python one. The program could poll the dev node in a loop,
> > which allows to conveniently check the impact of setting particular
> > triggers and all other brightness change events.
>
> Actually, I'd say that python is fine -- it is used heavily in tools/.
>
> But perhaps the example program should go to tools/?

I see python scripts only in perf tools. Let's stay by C application.

David, could you please prepare another version of the patch, that
splits test app code to the separate file in tools/leds (the directory
doesn't exist so far), also providing suitable Makefile?

> > > def change_brightness(b):
> > >    with open('/sys/class/leds/{}/brightness'.format(name) , 'w') as f:
> > >       f.write(str(b))
> > >
> > >
> > > with open('/dev/uleds', 'rb+', 0) as uleds:
> > >    bname = name.encode("ascii")
> > >    # create the leds class device
> > >    uleds.write(bname + b'\0' * (ULEDS_MAX_NAME_SIZE - len(bname)))
>
> Umm. I don't see it in the kernel code. You let userspace provide a
> LED name?
>
> Where is the LED name tested for sanity? I guess there could be a lot
> of fun naming a led ".." for example...

Good point.

--
Best regards,
Jacek Anaszewski