netdev - Re: [PATCH v1 1/6] staging: qlge: Initialize devlink health dump framework for the dlge driver

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Message-ID: <20201012112406.6mxta2mapifkbeyw@Rk>
Date:   Mon, 12 Oct 2020 19:24:06 +0800
From:   Coiby Xu <coiby.xu@...il.com>
To:     Benjamin Poirier <benjamin.poirier@...il.com>
Cc:     devel@...verdev.osuosl.org, Shung-Hsi Yu <shung-hsi.yu@...e.com>,
        Manish Chopra <manishc@...vell.com>,
        "supporter:QLOGIC QLGE 10Gb ETHERNET DRIVER" 
        <GR-Linux-NIC-Dev@...vell.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:QLOGIC QLGE 10Gb ETHERNET DRIVER" <netdev@...r.kernel.org>
Subject: Re: [PATCH v1 1/6] staging: qlge: Initialize devlink health dump
 framework for the dlge driver

On Sat, Oct 10, 2020 at 10:48:55PM +0900, Benjamin Poirier wrote:
>On 2020-10-10 18:24 +0800, Coiby Xu wrote:
>> On Sat, Oct 10, 2020 at 04:35:14PM +0900, Benjamin Poirier wrote:
>> > On 2020-10-08 19:58 +0800, Coiby Xu wrote:
>> > > Initialize devlink health dump framework for the dlge driver so the
>> > > coredump could be done via devlink.
>> > >
>> > > Signed-off-by: Coiby Xu <coiby.xu@...il.com>
>> > > ---
>> > >  drivers/staging/qlge/Kconfig        |  1 +
>> > >  drivers/staging/qlge/Makefile       |  2 +-
>> > >  drivers/staging/qlge/qlge.h         |  9 +++++++
>> > >  drivers/staging/qlge/qlge_devlink.c | 38 +++++++++++++++++++++++++++++
>> > >  drivers/staging/qlge/qlge_devlink.h |  8 ++++++
>> > >  drivers/staging/qlge/qlge_main.c    | 28 +++++++++++++++++++++
>> > >  6 files changed, 85 insertions(+), 1 deletion(-)
>> > >  create mode 100644 drivers/staging/qlge/qlge_devlink.c
>> > >  create mode 100644 drivers/staging/qlge/qlge_devlink.h
>> > >
>> > > diff --git a/drivers/staging/qlge/Kconfig b/drivers/staging/qlge/Kconfig
>> > > index a3cb25a3ab80..6d831ed67965 100644
>> > > --- a/drivers/staging/qlge/Kconfig
>> > > +++ b/drivers/staging/qlge/Kconfig
>> > > @@ -3,6 +3,7 @@
>> > >  config QLGE
>> > >  	tristate "QLogic QLGE 10Gb Ethernet Driver Support"
>> > >  	depends on ETHERNET && PCI
>> > > +	select NET_DEVLINK
>> > >  	help
>> > >  	This driver supports QLogic ISP8XXX 10Gb Ethernet cards.
>> > >
>> > > diff --git a/drivers/staging/qlge/Makefile b/drivers/staging/qlge/Makefile
>> > > index 1dc2568e820c..07c1898a512e 100644
>> > > --- a/drivers/staging/qlge/Makefile
>> > > +++ b/drivers/staging/qlge/Makefile
>> > > @@ -5,4 +5,4 @@
>> > >
>> > >  obj-$(CONFIG_QLGE) += qlge.o
>> > >
>> > > -qlge-objs := qlge_main.o qlge_dbg.o qlge_mpi.o qlge_ethtool.o
>> > > +qlge-objs := qlge_main.o qlge_dbg.o qlge_mpi.o qlge_ethtool.o qlge_devlink.o
>> > > diff --git a/drivers/staging/qlge/qlge.h b/drivers/staging/qlge/qlge.h
>> > > index b295990e361b..290e754450c5 100644
>> > > --- a/drivers/staging/qlge/qlge.h
>> > > +++ b/drivers/staging/qlge/qlge.h
>> > > @@ -2060,6 +2060,14 @@ struct nic_operations {
>> > >  	int (*port_initialize)(struct ql_adapter *qdev);
>> > >  };
>> > >
>> > > +
>> > > +
>> > > +struct qlge_devlink {
>> > > +        struct ql_adapter *qdev;
>> > > +        struct net_device *ndev;
>> >
>> > This member should be removed, it is unused throughout the rest of the
>> > series. Indeed, it's simple to use qdev->ndev and that's what
>> > qlge_reporter_coredump() does.
>>
>> It reminds me that I forgot to reply to one of your comments in RFC and
>> sorry for that,
>> > > +
>> > > +
>> > > +struct qlge_devlink {
>> > > +        struct ql_adapter *qdev;
>> > > +        struct net_device *ndev;
>> >
>> > I don't have experience implementing devlink callbacks but looking at
>> > some other devlink users (mlx4, ionic, ice), all of them use devlink
>> > priv space for their main private structure. That would be struct
>> > ql_adapter in this case. Is there a good reason to stray from that
>> > pattern?
>
>Thanks for getting back to that comment.
>
>>
>> struct ql_adapter which is created via alloc_etherdev_mq is the
>> private space of struct net_device so we can't use ql_adapter as the
>> the devlink private space simultaneously. Thus struct qlge_devlink is
>> required.
>
>Looking at those drivers (mlx4, ionic, ice), the usage of
>alloc_etherdev_mq() is not really an obstacle. Definitely, some members
>would need to be moved from ql_adapter to qlge_devlink to use that
>pattern.
>
I see what you mean now. I thought we were going to use struct ql_adapter
as the shared private structure of devlink and net_device. If we are
going to use ql_adapter as the private structure of devlink then we have
to define another private structure for net_device.

>I think, but didn't check in depth, that in those drivers, the devlink
>device is tied to the pci device and can exist independently of the
>netdev, at least in principle.
>
You are right. Take drivers/net/ethernet/mellanox/mlxsw as an example,
devlink reload would first first unregister_netdev and then
register_netdev but struct devlink stays put. But I have yet to
understand when unregister/register_netdev is needed. Do we need to
add "devlink reload" for qlge?

>In any case, I see now that some other drivers (bnxt, liquidio) have a
>pattern similar to what you use so I guess that's acceptable too.

--
Best regards,
Coiby