On Mon, Aug 22, 2022 at 01:21:47PM +0000, Gupta, Nipun wrote: > [AMD Official Use Only - General] > > > > > -----Original Message----- > > From: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> > > Sent: Wednesday, August 17, 2022 9:03 PM > > To: Gupta, Nipun <Nipun.Gupta@xxxxxxx> > > Cc: robh+dt@xxxxxxxxxx; krzysztof.kozlowski+dt@xxxxxxxxxx; rafael@xxxxxxxxxx; > > eric.auger@xxxxxxxxxx; alex.williamson@xxxxxxxxxx; cohuck@xxxxxxxxxx; > > Gupta, Puneet (DCG-ENG) <puneet.gupta@xxxxxxx>; > > song.bao.hua@xxxxxxxxxxxxx; mchehab+huawei@xxxxxxxxxx; maz@xxxxxxxxxx; > > f.fainelli@xxxxxxxxx; jeffrey.l.hugo@xxxxxxxxx; saravanak@xxxxxxxxxx; > > Michael.Srba@xxxxxxxxx; mani@xxxxxxxxxx; yishaih@xxxxxxxxxx; > > jgg@xxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; > > kvm@xxxxxxxxxxxxxxx; okaya@xxxxxxxxxx; Anand, Harpreet > > <harpreet.anand@xxxxxxx>; Agarwal, Nikhil <nikhil.agarwal@xxxxxxx>; > > Simek, Michal <michal.simek@xxxxxxx>; git (AMD-Xilinx) <git@xxxxxxx> > > Subject: Re: [RFC PATCH v2 2/6] bus/cdx: add the cdx bus driver > > > > [CAUTION: External Email] > > > > On Wed, Aug 17, 2022 at 08:35:38PM +0530, Nipun Gupta wrote: > > > CDX bus driver manages the scanning and populating FPGA > > > based devices present on the CDX bus. > > > > > > The bus driver sets up the basic infrastructure and fetches > > > the device related information from the firmware. These > > > devices are registered as platform devices. > > > > Ick, why? These aren't platform devices, they are CDX devices. Make > > them real devices here, don't abuse the platform device interface for > > things that are not actually on the platform bus. > > CDX is a virtual bus (FW based) which discovers FPGA based platform > devices based on communication with FW. virtual busses are fine to have as a real bus in the kernel, no problem there. > These devices are essentially platform devices as these are memory mapped > on system bus, but having a property that they are dynamically discovered > via FW and are rescannable. If they are dynamically discoverable and rescannable, then great, it's a bus in the kernel and NOT a platform device. > I think your point is correct in the sense that CDX bus is not an actual bus, > but a FW based mechanism to discover FPGA based platform devices. > > Can you kindly suggest us if we should have the CDX platform device scanning > code as a CDX bus in "drivers/bus/" folder OR have it in "drivers/fpga/" or > "drivers/platform/" or which other suitable location? drivers/cdx/ ? thanks, greg k-h
