[UPSTREAM] Move backlight handling out of pcf50633 driver

Sean McNeil sean at mcneil.com
Sun Oct 19 20:59:09 CEST 2008

Hi Mike,

Once again you get totally pissed off without explanation. As stated by
Andy, most software stacks use the sysfs value to get the
max_brightness. Tell us what breaks? If it is new code, why not check
max_brightness? 0-63 for brightness? Come on, anyone hard-coding for
this is guaranteed not to be portable to other platforms - even GTA03
possibly. 0-255, however, has been in many kernels, for many years and
has been thought to be a safe assumption.

So, explain yourself and stop ranting. What will break? I wanted a
#define so I could build a kernel for any desired max. Andy thinks we
should just go with what is a de-facto standard. Either is OK with me.

Mike (mwester) wrote:
> Balaji Rao wrote:
>>> It is unfortunate, but there are still some very high profile software
>>> stacks that assume brightness ranges from 0-255. A smaller amount that
>>> expects 0-100. These will get fixed over time, but it is nice to be able
>>> to specify an arbitrary max value in the kernel and have it scale
>>> appropriately. I can live with just making it a max of 255, though, as
>>> that is what I'm dealing with here.
>> Ah, ok. Making it take 256 values hurts none but helps many. If no one 
>> objects to this, I'll go ahead and do it.
> I find it amazing that nobody actually checks with the existing public
> distros that currently actually run on the GTA01 and GTA02 devices.
> I guess one can take solace in the thought that this interface change
> will ensure that EVERYTHING that currently runs will probably break --
> at least that's fair, right?
> My thought (not that it counts for much here) is that until the person
> who is WANTING TO CHANGE AN EXISTING ABI makes the effort to check what
> the impact is on the EXISTING and RUNNING distros and software for the
> device, NO CHANGE should be made.
> So, go ahead and change it -- but don't be surprised if it pisses off
> yet more unhappy and frustrated users who have written code and expect
> (reasonably) that it should run on a newer kernel, especially when the
> newer kernel is just a minor update....
> (Oh -- and perhaps someone can clarify why any user of the GTA01 or
> GTA02 cares about this "very high profile software stack" more than they
> care about the software that they currently run on the device???  That's
> hardly a justification for ABI breakage, especially when these so-called
> "very high profile software stacks" are not named.)
> Once again, that attitude of STICK IT TO THE USERS!   C'mon Openmoko --
> Mike (mwester)

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