@Maxdamantus: thanks a lot for that information.

@Pali: any chance of adding a kernel parameter kernel-power for this? This way one could, at his own risk, set-up an u-boot entry with this parameter to use as/when needed.

Oh, I just noted that omap_hsmmc is an actual module (not built-in the kernel), so this parameter could be set in /etc/init.d/ke-recv (and optionally in softupd.rcS).

So the module parameter could be set from the kernel command line or directly on the script loading the module (like "/etc/default/unmount_sd_when_cover_off" having "true" or "false").