To test the host controller and bus management code, it is currently required to have a physical SoundWire peripheral attached to the bus. To help with pre-silicon or early hardware enablement, it would be very useful to have a SoundWire 'mockup' device that is exposed in platform firmware but does not drive any signal on the bus. This is different to the existing ASoC 'dummy' codec uses for I2S/TDM, the SoundWire spec makes it clear that a device that is not attached to the bus is not permitted to interact with the bus, be it for command/control or data. This patch exposes a 'mockup' device, with a minimalist driver, with 4 partID values reserved by Intel for such test configurations. The mockup device exposes one full-duplex DAI based on 2 ports (DP1 for playback and DP8 for capture). The capture data port is just virtual, such a mockup device is prevented by the SoundWire specification from presenting any data generated by a Source port without being Attached. All the callbacks exposed by the SoundWire Slave interface are populated, even if they just return immediately. This is intentional to describe what a minimal codec driver should do and implement and help new codec vendors provide support for their devices. Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> Reviewed-by: Rander Wang <rander.wang@intel.com> Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com> Link: https://lore.kernel.org/r/20210714032209.11284-2-yung-chuan.liao@linux.intel.com Signed-off-by: Mark Brown <broonie@kernel.org>