Hi Greg, > Subject: Re: [PATCH v2 1/3] platform/x86: Add Intel Input Output Manager > (IOM) driver > > Hi Greg, > > On Fri, Aug 28, 2020 at 09:43:59AM +0200, Greg Kroah-Hartman wrote: > > I still find this crazy that a whole separate driver is created just > > to read a single 32bit value. > > > > Why not put this logic in the driver that wants to read that value? > > That would be much simpler, smaller, and more obvious. > > That would mean that we start maintaining something like DMI quirk table in > those drivers. Unfortunately the IOM device is not available on every > platform. > Also, even on platforms that do have it, there is no guarantee that the > device is > always going to be mapped to the same address. > > Nevertheless, I was originally hoping that we could hide the handling of IOM > somehow in ACPI without the need for an actual device object, but it now > turns out that the other features of the IOM chip have created interest. At > least our i915 guys probable have some use for it (I don't know exactly what > they are planning to use it for). > > So the fact that we may later need the device for something else, on top of > the > clumsiness and most importantly risks involved with using ACPI to take care of > extra tasks (ASL tends to have bugs - bugs that may never ever get fixed), I > think the IOM device object, and the driver that binds to it, do have a valid > reason for existing. >
Intel PMC USB mux device is part of the PCH, while IOM is part of the SoC. This was another reason we had to have a separate ACPI device. > > thanks, > > -- > heikki
