[PATCH] Keyboard backlight driver for Oct 2005 PowerBooks

Michael Hanselmann linux-kernel at hansmi.ch
Mon Aug 28 09:24:52 EST 2006

On Mon, Aug 28, 2006 at 09:11:03AM +1000, Benjamin Herrenschmidt wrote:
> > Drivers are there to abstract hardware. Userland shouldn't know about
> > hardware specific commands (PMU commands in this case).

> This is a bit of a broad statement :) If I were to follow you, thinks
> like USB scanner or printer drivers should all be in the kernel :)
> Well... they happen not to be.

True. But then again, a printer driver does little more than configuring
a single PWM value.

If there wasn't an I²C variant, we could even export these things as PMU
sub-devices. But there is one and a driver could easily hide these
differences from userland, because they simply don't matter there.

> Then the best is to do a library.

There was some effort ongoing on that a few months ago (at least on
IRC). Was there anything coming out of it?

> Yeah, separate program or library would do the trick just fine. Also,
> your driver doesn't handle reading the light sensors, does it ?

No, it doesn't. The light sensor is a different device and doesn't
belong into a LED driver. I plan to do a driver for it separately.

So the target is to have one driver for backlight and one for sensors,
each handling the I²C and PMU variants. MacBooks have some other
variant, which could be included, theoretically. Lacking the hardware, I
can't do that, tough.

The main reason I did not do all at once is that I feared a discussion
like we have it now. I'm not going to invest much time for unused code
anymore like I did with the ctrl+click patch.


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