I was going through this patch of ours "gralloc: Use FBIOPAN_DISPLAY instead of FBIOPUT_VSCREENINFO to refresh display" http://android.git.linaro.org/gitweb?p=platform/hardware/libhardware.git%3Ba... and was wondering if we need to update this patch. The rationale behind this patch is that the PUT_VSCREENINFO implementation of iMX53 Fb driver was broken at that time https://bugs.launchpad.net/linaro-android/+bug/824506 so we switched to PAN_DISPLAY.

Here is an old but relevant discussion on this topic on android-porting list https://groups.google.com/d/msg/android-porting/6Tn36GpVWJI which say that the correct way to go forward is PAN_DISPLAY and put PUT_VSCREENINFO as a fallback option. Which sounds about right.

The only thing which is confusing here is that the fb kernel documentation suggest to use PAN_DISPLAY if we want to pan the screen only (i.e. only xoffset and/or yoffset are modified) and use PUT_VSCREENINFO otherwise. And in this particular case we modify other screen info variables as well (e.g. activate), should we still be doing PAN_DISPLAY then?

Regards, Amit Pundir