Hi moritz: On Sun, Sep 27, 2020 at 04:36:47PM +0800, Xu Yilun wrote: > Hi Greg, > > On Sun, Sep 27, 2020 at 09:54:01AM +0200, Greg KH wrote: > > On Sun, Sep 27, 2020 at 03:37:54PM +0800, Xu Yilun wrote: > > > Hi Greg, > > > > > > On Sun, Sep 27, 2020 at 07:51:08AM +0200, Greg KH wrote: > > > > On Sat, Sep 26, 2020 at 12:22:19PM -0700, Moritz Fischer wrote: > > > > > Hi Greg, > > > > > > > > > > On Sat, Sep 26, 2020 at 08:09:13AM +0200, Greg KH wrote: > > > > > > 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 :) > > > > > > > > > > Let's leave it as is -- An FPGA is one possible implementation and as for > > > > > other buses, you wouldn't call it fpga-usb or usb-fpga just because the > > > > > USB bus is implemented in an FPGA if it behaves like a normal USB bus. > > > > > Having an ASIC based DFL bus show up under dfl-fpga / fpga-dfl in sysfs > > > > > would be super confusing. > > I thought we have consensus that "dfl" could be used out of fpga domain. > And we are all good that we keep the user ABIs & the bus name - "dfl", so "dfl" > is good as a global name from linux user's point of view, is it? > > But why we reject the "dfl" in kernel code domain? I thought it is very > similar situation. > > > I think we have 2 options, to make the dfl self-consistent: > > 1. "dfl-fpga" for everything - bus name, user ABIs, structures & APIs for > other kernel subsystems. Then we lose the chance to support ASIC based DFL, > it would be hard if we change user ABIs later. > > 2. "dfl" for everything. > > BTW, no ASIC based DFL devices in kernel today. > > I fully understand the word "naming is hard" now, help me :) Seems now we have different opinions on this: - Hao thinks self-consistent is important to dfl framework. - "dfl" for everything seems not preferable to Greg. - From your previous mail, I assume you prefer to keep the bus name as "dfl" but change the stuff for other subsystem, is it? So I got a little stuck here. Do you think "dfl-fpga" for everything would be an acceptable solution for you? Thanks, Yilun > > > > > > > > > > > > > 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? > > > > > > DFL is a method to discover devices. If a different subsystem (e.g. ASIC based > > > DFL bus) want to use DFL and follows the DFL spec, they could just use the DFL > > > stuff for enumeration, no need to have new variants. > > > > > > > > > > > > > > > And why didn't you all use device tree? How did this sneak in past > > > > > > everyone? > > > > > > > > > > DFL is a pretty efficient implementation in terms of resource > > > > > utilization on the FPGA end (a couple of registers / memories) vs > > > > > several kilobytes of memory for a device-tree blob. > > > > > > > > > > The hardware using DFL to describe its internal structure exists in the > > > > > form of deployed accelerator cards and telling all its users to go and > > > > > change their hardware design would be feasible -- If you think about an > > > > > FPGA as a (albeit reconfigurable) ASIC you wouldn't go and tell people > > > > > to redesign their ASIC to use Device-Tree? :) > > > > > > > > > > I'm not sure where the 'sneaking in' anything comes from. It's been > > > > > reviewed on the list (and by yourself back then). If you feel any of > > > > > this wasn't kosher, let's talk about it, to make sure it doesn't happen > > > > > again. > > > > > > > > I can't remember reviewing it, sorry, too many patches, I probably was > > > > only worrying about functionality issues, not what the code actually did > > > > :) > > > > > > > > So it's fine, just a surprise to me, no big deal. > > > > > > I'm glad that we made it clear. And the bus name & user APIs cound be > > > kept as "dfl". So I assume the name "dfl" is OK to be used and could > > > be recognized by people out of FPGA domain, is it? > > > > > > If so, I still want to keep the name "dfl_device_id" in mod_devicetable.h > > > as well. > > > > No, this is specific to the fpga subsystem, right? So please put fpga > > in the name. > > I put my comments under Moritz's lines above, hope it makes clear. > > > > > > We want to keep the device id name of the bus aligned with the > > > bus name. And it would be confusing as well if a driver for ASIC based > > > DFL device uses the "dfl_fpga_device_id" structure. > > > > Do we have that in the kernel today? > > Actually no. > > Thanks, > Yilun > > > > > thanks, > > > > greg "naming is hard" k-h
