VK_BAR_CHAN_WR
vktty->wr = vkread32(vk, BAR_1, VK_BAR_CHAN_WR(vktty, to));
vkwrite32(vk, vktty->wr, BAR_1, VK_BAR_CHAN_WR(vktty, to));
wr = vkread32(vk, BAR_1, VK_BAR_CHAN_WR(vktty, from));