linux-kernel - Re: [PATCH] leds: Introduce userspace leds driver

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Date:   Thu, 15 Sep 2016 14:41:03 +0200
From:   Pavel Machek <pavel@....cz>
To:     Jacek Anaszewski <j.anaszewski@...sung.com>
Cc:     David Lechner <david@...hnology.com>,
        Richard Purdie <rpurdie@...ys.net>,
        linux-kernel@...r.kernel.org, linux-leds@...r.kernel.org,
        Marcel Holtmann <marcel@...tmann.org>
Subject: Re: [PATCH] leds: Introduce userspace leds driver

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/?

> >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...

Best regards,
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html