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

From: Bryan Wu
Date: Thu Jan 02 2014 - 19:17:09 EST

On Sun, Dec 29, 2013 at 3:21 AM, Pavel Machek <pavel@xxxxxx> wrote:
> Hi!
>> > 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?

What about send those binary stuff as firmware through kernel firmware
interface and LED trigger sysfs is just for parameters setup and
enable/disable controlling.

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