Add VgaInb() helper function to read vga registers. With that in place
fix the unblanking. We need to put the ATT_ADDRESS_REGISTER flip flop
into a known state, which is done by reading the
INPUT_STATUS_1_REGISTER. Reading the INPUT_STATUS_1_REGISTER only works
when the device is in color mode, so make sure that bit (0x01) is set in
MISC_OUTPUT_REGISTER.
Currently the mode setting works more by luck because
ATT_ADDRESS_REGISTER flip flop happens to be in the state we need.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
512042eba8