Re: [PATCH v3 1/5] fpga: dfl: rename the bus type "dfl" to "fpga-dfl"

[Greg KH]

On Sat, Sep 26, 2020 at 10:23:46AM +0800, Xu Yilun wrote:
> Hi greg,
> 
> About the bus naming, I summarized some questions we've discussed to check
> with you. See inline.
> 
> On Thu, Sep 24, 2020 at 10:27:00AM -0700, Moritz Fischer wrote:
> > Hi Xu,
> > 
> > On Fri, Sep 25, 2020 at 12:59:57AM +0800, Xu Yilun wrote:
> > > Now the DFL device drivers could be made as independent modules and put
> > > in different subsystems according to their functionalities. So the name
> > > should be descriptive and unique in the whole kernel.
> > > 
> > > The patch changes the naming of dfl bus related structures, functions,
> > > APIs and documentations.
> > > 
> > > Signed-off-by: Xu Yilun <yilun.xu@xxxxxxxxx>
> > > ---
> > >  Documentation/ABI/testing/sysfs-bus-dfl      |  15 --
> > >  Documentation/ABI/testing/sysfs-bus-fpga-dfl |  15 ++
> > >  MAINTAINERS                                  |   2 +-
> > >  drivers/fpga/dfl.c                           | 254 ++++++++++++++-------------
> > >  drivers/fpga/dfl.h                           |  77 ++++----
> > >  5 files changed, 184 insertions(+), 179 deletions(-)
> > >  delete mode 100644 Documentation/ABI/testing/sysfs-bus-dfl
> > >  create mode 100644 Documentation/ABI/testing/sysfs-bus-fpga-dfl
> > > 
> > > diff --git a/Documentation/ABI/testing/sysfs-bus-dfl b/Documentation/ABI/testing/sysfs-bus-dfl
> > > deleted file mode 100644
> > > index 23543be..0000000
> > > --- a/Documentation/ABI/testing/sysfs-bus-dfl
> > > +++ /dev/null
> > > @@ -1,15 +0,0 @@
> > > -What:		/sys/bus/dfl/devices/dfl_dev.X/type
> > > -Date:		Aug 2020
> > > -KernelVersion:	5.10
> > > -Contact:	Xu Yilun <yilun.xu@xxxxxxxxx>
> > > -Description:	Read-only. It returns type of DFL FIU of the device. Now DFL
> > > -		supports 2 FIU types, 0 for FME, 1 for PORT.
> > > -		Format: 0x%x
> > > -
> > > -What:		/sys/bus/dfl/devices/dfl_dev.X/feature_id
> > > -Date:		Aug 2020
> > > -KernelVersion:	5.10
> > > -Contact:	Xu Yilun <yilun.xu@xxxxxxxxx>
> > > -Description:	Read-only. It returns feature identifier local to its DFL FIU
> > > -		type.
> > > -		Format: 0x%x
> > 
> > You're changing userland facing ABI. I think that's something to avoid,
> > please check with Greg on the rules since this hasn't been in a release yet.
> > 
> 
> I'm going to change the name of bus stuff for other subsystems, to be
> aligned, I also consider change the bus_type.name and dfl dev_name. But
> it will cause the changing of user ABIs. No user case for these user ABI
> now cause they are just queued, is it good I change them?

Why change the user name here?  No need for that, right?  Unless you
really want to, and think that no one will notice.  If so, fine, change
them :)

> It is mentioned that although Device Feature List is introduced in FPGA,
> but it doesn't limit the usage in FPGA only. It's just a method to
> discover features from a device, for sure it can be extended and used
> in other devices too. So it can be bigger namespace than FPGA. Like in
> our existing code, we picked dfl_fpga (DFL based FPGA) for uapi (ioctl)
> and internal functions. This is suggested by Alan (The previous FPGA
> maintainer). It's possible to have "DFL based XXX" in the future, even
> currently only FPGA uses DFL. This is the reason we thought just "dfl"
> in the whole kernel space is OK.
> So, is there a chance we keep the "dfl" naming in the whole kernel?

No one knows what "DFL" is, and odds are, if a different subsystem wants
to use it, they will have their own variant, right?

And why didn't you all use device tree?  How did this sneak in past
everyone?

thanks,

greg k-h