not a direct answer to your mail but very related and raising other questions / problems:
jessie kernel already supports simplefb (simple framebuffer) together with newer u-boot, specific u-boot environment and a custom device tree it is possible to get a framebuffer. The specific u-boot environment is needed for the lcd display settings/timings. Would it be an option to build different u-boot configurations for the different board+display combinations? The custom device tree is needed to make the touchscreen known. It looks like such a device tree won't be accepted in mainline and one should use device tree overlays. Is there anything related already in debian? example here: http://karme.de/prisirah/ ┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┯━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓ ┃ Setup │ U‑Boot file name ┃ ┠──────────────────────────────────┼──────────────────────────────────────┨ ┃ A20‑OLinuXino‑MICRO │ ┃ ┃ + LCD‑OLinuXino‑7TS (or │ u-boot-A20-OLinuXino_MICRO-lcd7.bin ┃ ┃ A13‑LCD7‑TS) │ ┃ ┠──────────────────────────────────┼──────────────────────────────────────┨ ┃ A20‑OLinuXino‑MICRO │ ┃ ┃ + LCD‑OLinuXino‑10TS (or │ u-boot-A20-OLinuXino_MICRO-lcd10.bin ┃ ┃ A13‑LCD10‑TS) │ ┃ ┠──────────────────────────────────┼──────────────────────────────────────┨ ┃ A20‑OLinuXino‑MICRO + HDMI/DVI/ │ u-boot-A20-OLinuXino_MICRO.bin ┃ ┃ VGA │ ┃ ┠──────────────────────────────────┼──────────────────────────────────────┨ ┃ A20‑OLinuXino‑LIME2 │ u-boot-A20-OLinuXino-Lime2-lcd7.bin ┃ ┃ + LCD‑OLinuXino‑7TS │ ┃ ┠──────────────────────────────────┼──────────────────────────────────────┨ ┃ A20‑OLinuXino‑LIME2 │ u-boot-A20-OLinuXino-Lime2-lcd10.bin ┃ ┃ + LCD‑OLinuXino‑10TS │ ┃ ┠──────────────────────────────────┼──────────────────────────────────────┨ ┃ A20‑OLinuXino‑LIME2 + HDMI/DVI │ u-boot-A20-OLinuXino-Lime2.bin ┃ ┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┷━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛
