On 18/12/2020 16:58:56-0400, Jason Gunthorpe wrote: > On Fri, Dec 18, 2020 at 08:32:11PM +0000, Mark Brown wrote: > > > > So, I strongly suspect, MFD should create mfd devices on a MFD bus > > > type. > > > > Historically people did try to create custom bus types, as I have > > pointed out before there was then pushback that these were duplicating > > the platform bus so everything uses platform bus. > > Yes, I vaugely remember.. > > I don't know what to say, it seems Greg doesn't share this view of > platform devices as a universal device. > > Reading between the lines, I suppose things would have been happier > with some kind of inheritance scheme where platform device remained as > only instantiated directly in board files, while drivers could bind to > OF/DT/ACPI/FPGA/etc device instantiations with minimal duplication & > boilerplate. > > And maybe that is exactly what we have today with platform devices, > though the name is now unfortunate. > > > I can't tell the difference between what it's doing and what SOF is > > doing, the code I've seen is just looking at the system it's running > > on and registering a fixed set of client devices. It looks slightly > > different because it's registering a device at a time with some wrapper > > functions involved but that's what the code actually does. > > SOF's aux bus usage in general seems weird to me, but if you think > it fits the mfd scheme of primarily describing HW to partition vs > describing a SW API then maybe it should use mfd. > > The only problem with mfd as far as SOF is concerned was Greg was not > happy when he saw PCI stuff in the MFD subsystem. > But then again, what about non-enumerable devices on the PCI device? I feel this would exactly fit MFD. This is a collection of IPs that exist as standalone but in this case are grouped in a single device. Note that I then have another issue because the kernel doesn't support irq controllers on PCI and this is exactly what my SoC has. But for now, I can just duplicate the irqchip driver in the MFD driver. > This whole thing started when Intel first proposed to directly create > platform_device's in their ethernet driver and Greg had a quite strong > NAK to that. Let me point to drivers/net/ethernet/cadence/macb_pci.c which is a fairly recent example. It does exactly that and I'm not sure you could do it otherwise while still not having to duplicate most of macb_probe. -- Alexandre Belloni, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
