Ability to rotate the display without Xorg (framebuffer with GBM/KMS)

[natinusala]

There is currently no way to rotate the fb0 framebuffer (used with GBM/KMS).

• echo 3 > /sys/class/graphics/fb0/rotate flickers the screen but doesn't actually do anything
• fbcon is however correctly rotated, as you already know
• our application (RetroArch) sees a framebuffer of 720x1280px
• fbset (of busybox 1.25.1) gives :
  • a 720x1280px screen instead of 1280x720px
  • all timings are set to 0
  • fbset can't be used to change the resolution because of an ioctl issue
  • however, fbset seems to be outdated - see this issue