-----Original Message----- From: Pierre-Louis Bossart pierre-louis.bossart@linux.intel.com Sent: Thursday, October 1, 2020 7:07 AM To: Mark Brown broonie@kernel.org; Ertman, David M david.m.ertman@intel.com Cc: alsa-devel@alsa-project.org; tiwai@suse.de; gregkh@linuxfoundation.org; Sridharan, Ranjani ranjani.sridharan@intel.com; parav@nvidia.com; jgg@nvidia.com Subject: Re: [PATCH 0/6] Ancillary bus implementation and SOF multi-client support
are controlled by DT/ACPI. The same argument applies for not using MFD in this scenario as it relies on individual function devices being physical devices that are DT enumerated.
MFD has no reliance on devices being DT enumerated, it works on systems that don't have DT and in many cases it's not clear that the split you'd want for the way Linux describes devices is a sensible one for other operating systems so we don't want to put it into DT. Forcing things to be DT enumerated would just create needless ABIs.
I agree the "DT enumerated" part should be removed.
To the best of my knowledge, the part of 'individual function devices being physical devices' is correct though. MFDs typically expose different functions on a single physical bus, and the functions are separated out by register maps. In the case where there's no physical bus/device and no register map it's unclear how MFDs would help?
The MFD bus also uses parts of the platform bus in the background, including platform_data and the such. We submitted a version of the RDMA/LAN solution using MFD and it was NACK'd by GregKH.
-DaveE