drivers/built-in.o: In function `exynos_drm_attach_lcd_bridge':
.../drivers/gpu/drm/exynos/exynos_dp_core.c:1004:
undefined reference to `ptn3460_init'
This is because ptn3460_init can't be implemented in a module while
its caller is built into the kernel. So add the proper dependency in
Kconfig so that the above can't happen.
I moved DRM_PTN3460 earlier in Kconfig, next to the I2C helper module
section, so that the user has a chance to select it before moving to
the Exynos-specific section.
IMHO the proper way to solve the problem would be to turn ptn3460 into
a clean I2C driver, similar to the other I2C helper chip drivers. It's
the only way to not sink into impossible-to-guess dependencies. Then
ptn3460 could even be moved together with the other I2C helper chip
drivers.