Re: how to represent sequence of brightnesses in /sys (was Re:[PATCH] Add the LED burst trigger)

From: Pavel Machek
Date: Sun Dec 29 2013 - 06:21:41 EST


> > Idea would be "sequence of brigtnesses" (one file) and "delay between
> > changes" (second file).
> Ick.
> > Reason to do it in kernel is that some machines actually have
> > "coprocessor" on i2c that can do it while main CPU is suspended. (For
> > more reasons, see beggining of thread).
> Ick ick.
> > Binary attribute with array of bytes should be acceptable, rights?
> Not at all.
> > (IOW write(..., buf, size) )
> >
> > Ascii array of decimal integers -- no so, right?
> >
> > (IOW printf("%d %d ..", buf[0], buf[1]) )
> Use an ioctl with a structure to get things correct as a character
> device. As odds are, you aren't going to be able to create a "generic"
> format for all of this for all types of devices that support such a
> "co-processor".

Well, we already do have hw-specific driver in the tree,
drivers/leds/leds-lp55xx-common.c . But the interface is
"interesting" and I believe we should have generic interface and it
should use existing trigger framework -- array of brightnesses does
not seem too complicated.

Do you have suggestion how to pass the brightnesses over sysfs?

(cesky, pictures)
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at