Comment 3 for bug 1187867

There are two problems here. I don't believe either of them are powerd's.

1. Setting the backlight level to 0 doesn't disable it, and it doesn't disable when the fb is blanked either. The only way to actually turn it off seems to be to suspend. I've got a kernel patch that makes brightnes=0 == screen off which at least masks the issue, but I'm still wondering what Android does.

Okay, so it turns out Android does exactly what my patch does. Apparently we patched the kernel a long time ago so that 0 brightness doesn't turn the screen off. I'll change it back.

2. Something in the graphics driver is failing to suspend. So what happens is that the kernel keeps trying to suspend over and over again. Each time some of the devices suspend, then the graphics driver fails and the already suspended devices are resumed. One of the ones getting repeatedly suspended and resumed is the backlight device, which is what causes it to cycle on and off. It's masked by my patch for issue #1, but fixing the failed suspends will require more investigation.