The config patches for the latest mainline V4.11 Ubuntu builds (as in http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.11-rc3/ for example) omit setting CONFIG_HDMI_LPE_AUDIO which is required for the new audio support over HDMI patch set included in v4.11 specifically for BYT/CHT SoC based Intel devices. Currently as CONFIG_SND_X86 is unset then CONFIG_HDMI_LPE_AUDIO is not defined.
Change request: Set CONFIG_SND_X86=m and CONFIG_HDMI_LPE_AUDIO=m in the configs for v4.11 mainline builds so audio over HDMI will work for BYT/CHT SoC based Intel devices in addition to existing devices where audio over HDMI works by default. This is a result of a new driver introduced in v4.11. The current v4.11 config is defined from patch 0006-configs-based-on-Ubuntu-4.10.0-6.8.patch (see http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.11-rc3/0006-configs-based-on-Ubuntu-4.10.0-6.8.patch) and this patch would require regenerating with the addition of CONFIG_SND_X86=m and CONFIG_HDMI_LPE_AUDIO=m