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    SubjectRe: best way to handle LEDs
    On Wed, November 2, 2005 3:51 am, Pavel Machek said:
    > Hi!
    >> > I think even slow blinking was used somewhere. I have some code from
    >> > John Lenz (attached); it uses sysfs interface, exports led collor, and
    >> > allows setting different frequencies.
    >> >
    >> > Is that acceptable, or should some other interface be used?
    >> there is already an LED interface for linux-arm, which is
    >> used by a number of the extant machines in the sa11x0 and
    >> pxa range.
    > Where is that interface? I think that making collie use it is obvious
    > first step...
    > Pavel

    I originally wrote the collie led code to use that interface, and you
    might look at some of the old versions of the patch on my web site. The
    actual code is in arch/arm/kernel/time.c, but this code calls out to an
    individual machine function through say arch/arm/mach-sa1100/leds.c...
    The problem for collie was that the device model for locomo did not allow
    an easy way to do it... as you can see, in my patch it implements a driver
    for those leds and the driver model takes care of it.

    I just looked, and contins
    the implementation of the arm led interface for collie.... not sure if it
    will still work anymore, but...

    I then grew the led code to support more than four leds, multi color leds,
    more than just the arm architecture, etc... Russell has been very critical
    of my patch on the "waste" of memory (a struct device for each led, along
    with a bunch of struct attributes for each led), where by contrast the arm
    one has a single attribute.

    But this led interface and the one arm provides can almost not even be
    compared. My patch correctly implements the sysfs model of one attribute,
    one file (instead of all leds controlled through a single file). My patch
    also is more flexible and provides needed options for many leds. The
    downside is, it makes the leds hard to use for debugging, which is the
    primary purpose of the original arm led code.

    For debugging, the arm specific led code is a great tool, and I am not
    meaning to replace it. For debugging, you can just specifiy


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