H3 : mmap to /dev/fb0 failed after change resolution

Hello all, just new to here, I bought an Orangepi PC board and grabbed lastest Armbian pre-built image with legacy kernel.

I test my code that dynamically change the HDMI output resolution,  by something like this:

ioctl(disp, DISP_BLANK, true)

ioctl(disp, DISP_DEVICE_SWITCH)

ioctl(disp, DISP_BLANK, false)

and then update fbvar by ioctl(fb0, FBIOPUT_VSCREENINFO)

I can see output actually changed, everything goes well until I try to map framebuffer from /dev/fb0, it failed with errno EINVAL.

After check drivers source code I think it's because the display driver, it forget to notify the system to update framebuffer parameters, but I can't figure out the actual problem of the code.

If I use h3disp, after reboot I can map framebuffer as well, but I need to change it dynamically. Does anyone have a solution for this? Thank you very much!