Questions about the backlight do not appear to have been addressed elsewhere.  For the record, I'm using an Earth and Palo 43, with the v0.92 palmtop image from http://www.gumstix.net/overo-gm-images/, which has backlight settings that don't, actually, control the backlight. (See missing driver, point 1, below). 
 
Here are my questions:
1) The backlight brightness is driven by a PWM (GPIO145_PWM10).  A PWM driver is not (apparently) available.  I can create the GPIO device (echo 145 > /sys/class/gpio/export; echo "out" > /sys/class/gpio/gpio145/direction, for those following along at home), but this only allows me to turn the backlight on or off (echo "1" > /sys/class/gpio/gpio145/value; echo "0"...).  QUESTION: how do I get control of the backlight as a PWM, instead?  (Please use small words; I'm a mechanical engineer by training, drowning in a world of CS bitbakes, linux, qt, and the like.  As a side note, my expectation was that these sorts of things were already available, so that I could focus on the interfaces with external equipment, which was the reason I got the Earth.)
2) I believe this is related, but... when my Earth goes to sleep, the screen is bright white (i.e., not sleeping).  I assume this stems from a broken (software) connection between the (missing) backlight device and the window manager.  Am I correct?  If/when I have a device that controls the backlight PWM, properly referenced, will this issue go away?  I'm using a Samsung 800x480, 4.8" touchscreen, so it's not exactly the same as the one sold directly by gumstix, but it's got (nearly) the same pinout (the backlight is currently bright enough using only one of the two sticks of LED's).
 
Thanks,
John