Re: [dpdk-dev] [EXT] Re: [PATCH v2 1/7] lib/librte_pci: add rte_pci_regs.h

[Jerin Jacob <jerinjacobk@gmail.com>]

On Sun, Jul 19, 2020 at 1:12 AM Manish Chopra <manishc@marvell.com> wrote:
>
> > -----Original Message-----
> > From: dev <dev-bounces@dpdk.org> On Behalf Of Manish Chopra
> > Sent: Friday, July 17, 2020 2:19 AM
> > To: Gaëtan Rivet <grive@u256.net>; Thomas Monjalon
> > <thomas@monjalon.net>
> > Cc: Jerin Jacob <jerinjacobk@gmail.com>; Ferruh Yigit
> > <ferruh.yigit@intel.com>; Igor Russkikh <irusskikh@marvell.com>; dpdk-dev
> > <dev@dpdk.org>
> > Subject: Re: [dpdk-dev] [EXT] Re: [PATCH v2 1/7] lib/librte_pci: add
> > rte_pci_regs.h
> >
> > > -----Original Message-----
> > > From: Gaëtan Rivet <grive@u256.net>
> > > Sent: Thursday, July 16, 2020 11:26 PM
> > > To: Thomas Monjalon <thomas@monjalon.net>
> > > Cc: Jerin Jacob <jerinjacobk@gmail.com>; Manish Chopra
> > > <manishc@marvell.com>; Ferruh Yigit <ferruh.yigit@intel.com>; Igor
> > > Russkikh <irusskikh@marvell.com>; dpdk-dev <dev@dpdk.org>
> > > Subject: [EXT] Re: [dpdk-dev] [PATCH v2 1/7] lib/librte_pci: add
> > > rte_pci_regs.h
> > >
> > > External Email
> > >
> > > ----------------------------------------------------------------------
> > > On 16/07/20 18:57 +0200, Thomas Monjalon wrote:
> > > > 16/07/2020 18:43, Jerin Jacob:
> > > > > On Thu, Jul 16, 2020 at 9:25 PM Thomas Monjalon
> > > <thomas@monjalon.net> wrote:
> > > > > >
> > > > > > 16/07/2020 15:02, Jerin Jacob:
> > > > > > > On Thu, Jul 16, 2020 at 6:20 PM Thomas Monjalon
> > > <thomas@monjalon.net> wrote:
> > > > > > > >
> > > > > > > > 16/07/2020 13:55, Jerin Jacob:
> > > > > > > > > On Thu, Jul 16, 2020 at 4:57 PM Thomas Monjalon
> > > <thomas@monjalon.net> wrote:
> > > > > > > > > >
> > > > > > > > > > 16/07/2020 12:27, Jerin Jacob:
> > > > > > > > > > > On Thu, Jul 16, 2020 at 3:48 PM Gaëtan Rivet
> > > <grive@u256.net> wrote:
> > > > > > > > > > > >
> > > > > > > > > > > > On 16/07/20 12:08 +0200, Gaëtan Rivet wrote:
> > > > > > > > > > > > > Re-CCing dev@dpdk.org as it was removed from the
> > reply.
> > > > > > > > > > > > >
> > > > > > > > > > > > > On 13/07/20 08:13 -0700, Manish Chopra wrote:
> > > > > > > > > > > > > > This is merely copy of latest linux/pci_regs.h
> > > > > > > > > > > > > > in order to avoid dependency of dpdk on user headers.
> > > > > > > > > > > > > >
> > > > > > > > > > > > >
> > > > > > > > > > > > > I guess this dependency is an issue on non-linux
> > > > > > > > > > > > > systems, when you must use those defines in a
> > > > > > > > > > > > > generic implementation. Can you confirm this is
> > > > > > > > > > > > > the
> > > motivation here?
> > > > > > > > > > > > >
> > > > > > > > > > > > > If so, I think it would be clearer to state "in
> > > > > > > > > > > > > order to avoid dependency of DPDK on linux headers".
> > > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > > > To add to it, if this is actually the motivation to
> > > > > > > > > > > > add this header, I don't think it is sufficient.
> > > > > > > > > > > >
> > > > > > > > > > > > You can restrict the function definition to the
> > > > > > > > > > > > linux part of the PCI bus driver instead, using
> > > > > > > > > > > > stubs for other
> > > systems.
> > > > > > > > > > > >
> > > > > > > > > > > > > > Signed-off-by: Manish Chopra
> > > > > > > > > > > > > > <manishc@marvell.com>
> > > > > > > > > > > > > > Signed-off-by: Igor Russkikh
> > > > > > > > > > > > > > <irusskikh@marvell.com>
> > > > > > > > > > > > > > ---
> > > > > > > > > > > > > >  drivers/bus/pci/linux/pci_uio.c     |    2 +-
> > > > > > > > > > > > > >  drivers/bus/pci/linux/pci_vfio.c    |    2 +-
> > > > > > > > > > > > > >  drivers/net/bnx2x/bnx2x.h           |    2 +-
> > > > > > > > > > > > > >  drivers/net/hns3/hns3_ethdev_vf.c   |    2 +-
> > > > > > > > > > > > > >  drivers/vdpa/ifc/base/ifcvf_osdep.h |    2 +-
> > > > > > > > > > > > > >  lib/librte_pci/Makefile             |    1 +
> > > > > > > > > > > > > >  lib/librte_pci/meson.build          |    2 +-
> > > > > > > > > > > > > >  lib/librte_pci/rte_pci_regs.h       | 1075
> > > +++++++++++++++++++++++++++
> > > > > > > > > > > > > >  8 files changed, 1082 insertions(+), 6
> > > > > > > > > > > > > > deletions(-)  create mode 100644
> > > > > > > > > > > > > > lib/librte_pci/rte_pci_regs.h
> > > > > > > > > > > > > >
> > > > > > > > > > > > >
> > > > > > > > > > > > > [...]
> > > > > > > > > > > > >
> > > > > > > > > > > > > > diff --git a/lib/librte_pci/rte_pci_regs.h
> > > > > > > > > > > > > > b/lib/librte_pci/rte_pci_regs.h new file mode
> > > > > > > > > > > > > > 100644 index 000000000..1d11f4de5
> > > > > > > > > > > > > > --- /dev/null
> > > > > > > > > > > > > > +++ b/lib/librte_pci/rte_pci_regs.h
> > > > > > > > > > > > > > @@ -0,0 +1,1075 @@
> > > > > > > > > > > > > > +/* SPDX-License-Identifier: GPL-2.0 WITH
> > > > > > > > > > > > > > +Linux-syscall-note */
> > > > > > > > > > > > > > +/*
> > > > > > > > > > > > >
> > > > > > > > > > > > > This file is delivered alongside the PCI lib,
> > > > > > > > > > > > > targeting
> > > userspace.
> > > > > > > > > > > > > This seems to be an exception to the license
> > > > > > > > > > > > > policy described in license/README. Code shared
> > > > > > > > > > > > > between kernel and userspace is expected to be
> > > > > > > > > > > > > dual-licensed BSD-3
> > > and GPL-2.0.
> > > > > > > > > > > > >
> > > > > > > > > > > > > As it is a copy of Linux user includes,
> > > > > > > > > > > > > re-licensing it as BSD-3 as well is not possible.
> > > > > > > > > > > > >
> > > > > > > > > > > > > So I think it might require a techboard +
> > > > > > > > > > > > > governing board exception approval. Ferruh or
> > > > > > > > > > > > > Thomas, what do you
> > > think?
> > > > > > > > > > >
> > > > > > > > > > > I think, instead of importing GPL-2.0 file, We can add
> > > > > > > > > > > the constants as need by the DPDK as symbols start
> > > > > > > > > > > from RTE_PCI_*(It will fix up the namespace as well).
> > > > > > > > > >
> > > > > > > > > > If symbols can be found in /usr/include/, don't add anything.
> > > > > > > > >
> > > > > > > > > Not by default on all the distros. It is part of pciutils library.
> > > > > > > > > Moreover, we need these symbols for Windows OS as well.
> > > > > > > > > IMO, We should add absolute minimum constants that needed
> > > > > > > > > for DPDK as RTE_PCI_*
> > > > > > > >
> > > > > > > > I am for mandating the dependency instead of copying it.
> > > > > > >
> > > > > > > You mean _pciutils_ package as a mandatory dependency to  DPDK.
> > > > > >
> > > > > > There is already this dependency:
> > > > > >         #include <linux/pci_regs.h>
> > > > >
> > > > > I just checked in archlinux, PCI headers can be provided by
> > > > >
> > > > > # pacman -F /usr/include/pci/header.h usr/include/pci/header.h is
> > > > > owned by core/pciutils 3.7.0-
> > > > >
> > > > > # pacman -F /usr/include/linux/pci.h usr/include/linux/pci.h is
> > > > > owned by core/linux-api-headers 5.4.17-1
> > > > >
> > > > >
> > > > > > I'm missing the real justification for this patch.
> > > > >
> > > > > See below.
> > > > >
> > > > > > Is there some missing definitions?
> > > > > > Is there some environments where this file is missing?
> > > > > >
> > > > > > > > pciutils cannot be installed on Windows?
> > > > > > > > Why do you care about Windows?
> > > > > > > > I don't see any contribution for qede on Windows.
> > > > > > >
> > > > > > > You closely review the patch, it not about qede. The proposed
> > > > > > > file comes at lib/librte_pci/rte_pci_regs.h which is common to
> > > Windows.
> > > > > >
> > > > > > The series is for qede. I'm trying to understand the motivation.
> > > > >
> > > > > First version of qede driver sent with defined generic PCI symbols
> > > > > and generic PCI function like pci_find_next_ext_capability() in
> > > > > qede
> > > driver.
> > > >
> > > > That's a pity the v2 is not threaded with v1, I would have found
> > > > these explanations easily myself.
> > > >
> > > > > In the review, I suggested using generic rte_ function as
> > > > > a) It is not specific to qede.
> > > > > b) Other drivers also doing the same thing in their own driver
> > > > > space as there is no dpdk API for the same.
> > > > > This patches create generic API for pci_find_next_ext_capability()
> > > > > and remove duplicate implementation from the drivers.
> > > > > https://urldefense.proofpoint.com/v2/url?u=http-3A__patches.dpdk.o
> > > > > rg
> > > > >
> > >
> > _patch_73959_&d=DwIDaQ&c=nKjWec2b6R0mOyPaz7xtfQ&r=bMTgx2X48QVX
> > > yXOEL8
> > > > > ALyI4dsWoR-m74c5n3d-
> > > ruJI8&m=eNuzGYhB7u2Wzru3VeBTY7QDZSSb9VQ9eQXW56D4
> > > > > 64Y&s=eatY5xyw-474yS0cBJXyG7gLyPXFo243P2LmBDDsXd8&e=
> > > >
> > > > I agree it's good to have an API for such thing.
> > > >
> > > > So far such feature is supported in drivers on Linux, requiring only
> > > > Linux headers to be installed.
> > > > Do we need more?
> > > >
> > > >
> > >
> > > +1 to make it generic, no question here.
> > >
> > > On linux, the dependency is already there (either from linux headers
> > > or
> > > pciutils) to have the original. So including this header in DPDK is
> > > only useful for other OSes.
> > >
> > > I think right now we should only add pci_find_next_ext_capability()
> > > full implementation within linux part of PCI bus, other systems being
> > stubs.
> > >
> > > We can go with your suggestion Jerin about adding only the specific
> > > symbols needed, prefixed with RTE_, once we decide to have windows
> > support.
> > > Question is whether we need it right now. Is there a driver that would
> > > make use of it support more than linux currently?
> > >
> > > --
> >
> > I don't know if there are any drivers which will require this other than linux
> > as of today -
> >
> > My only motivation of adding these symbols in dpdk via rte_pci_regs.h (new
> > file in lib/librte_pci/) was to avoid any dependency of dpdk on
> > /usr/include/../pci_regs.h, since I was little unsure whether in all
> > distributions (linux/windows) supported will have the required PCI defines
> > available in /usr/include/../pci_regs.h file or not in order to implement
> > rte_pci_find_next_ext_capability().  (unless user to bound for updating
> > headers by mean of installing any latest _pciutils_/packages). Moreover, for
> > not just this API, but if going forward if we have to add any new APIs which
> > could rely/depend on PCI defines availability under /usr/include.
> >
> > From the discussion so far -
> >
> > 1. Define the function under drivers/bus/pci/linux/pci.c only and add
> > empty/stub implementation for windows/pci.c and bsd/pci.c ?
> > 2.  Just relying on /usr/include/ is perfectly okay without adding any defines
> > anywhere for now ?, it will just require <linux/pci_regs.h> inclusion in
> >      drivers/bus/pci/linux/pci.c. OR Shall I add (may be in
> > lib/librte_pci/rte_pci.h ?) only required PCI defines with RTE_ prefixed and
> > use them instead ?
> >
>
> Hello Gaetan/Jerin,
>
> Could you please comment on above - what's sufficient to be incorporated in v3 for now ?
> I will work on the changes accordingly.

I am for introducing a handful(Not the completed list, Only add what
is needed for DPDK) of PCI constants as RTE_PCI_ in our public API.
And implement rte_pci_find_next_ext_capability() as common routine as
it is not specific to Linux.(I.e reading the config registers should
be only Linux/Windows-specific)

I leave the final decision to PCI and other maintainers.




>
> Thanks,
> Manish