You could trace AOSP for how android framework handle the power key event.
As for the part how it talk with kernel driver, most of time, this is
handled in HAL, the DisplayManagerService would response to the PowerState
Change and call the setPowerMode function at SurfaceFlinger, and then
with these codes:
if (hwcHasApiVersion(mHwc, HWC_DEVICE_API_VERSION_1_4)) {
return (status_t)mHwc->setPowerMode(mHwc, disp, mode);
} else {
return (status_t)mHwc->blank(mHwc, disp, mode ==
HWC_POWER_MODE_OFF ? 1 : 0);
On hwcomposer, it would talk with kernel driver through ioctls like this:
ioctl(_contextAnchor->fbFd, FBIOBLANK, fb_blank);
For some devices, there may have sys nodes exported to control the screen
power， it depends on the reality of your kernel driver.
在 2016年12月1日星期四 UTC+8下午2:56:32，ranchu写道：
>
> Hello,
>
> I'm struglling for some days now to turn off screen.
> I can do that with "input keyevent 26", but I rather do it directly to
> kernel.
> If I had known which sysfs maybe is called on doing " input keyevent 26"
> it could have helped me a lot.
> Is it with ftrace ? ftrace not enabled in my manufacture's kernel.
>
> I made *many* trials in sort of "echo 0 > brightness", but I get only
> darker screen, but not a screen turned off.
>
> Trying to understand why "input keyevent 26" works, while others trials
> fails...
> I appreciate any feedback on this.
> I'm using android 5.1.1 with kernel 3.4.0-perf
>
> Regards,
> Ranchu
>
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