netdev - Re: [RFC PATCH 0/4] r8169: support dash

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Date:   Sat,  4 Dec 2021 02:08:29 +0100
From:   Alexander Lobakin <alexandr.lobakin@...el.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Alexander Lobakin <alexandr.lobakin@...el.com>,
        Hayes Wang <hayeswang@...ltek.com>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        nic_swsd <nic_swsd@...ltek.com>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>
Subject: Re: [RFC PATCH 0/4] r8169: support dash

From: Jakub Kicinski <kuba@...nel.org>
Date: Fri, 3 Dec 2021 07:04:10 -0800

> On Fri, 3 Dec 2021 07:57:08 +0000 Hayes Wang wrote:
> > Jakub Kicinski <kuba@...nel.org>
> > > I'm not sure how relevant it will be to you but this is the
> > > documentation we have:
> > > 
> > > https://www.kernel.org/doc/html/latest/networking/devlink/index.html
> > > https://www.kernel.org/doc/html/latest/networking/devlink/devlink-params.ht
> > > ml
> > > 
> > > You'll need to add a generic parameter (define + a short description)
> > > like 325e0d0aa683 ("devlink: Add 'enable_iwarp' generic device param")
> > > 
> > > In terms of driver changes I think the most relevant example to you
> > > will be:
> > > 
> > > drivers/net/ethernet/ti/cpsw_new.c
> > > 
> > > You need to call devlink_alloc(), devlink_register and
> > > devlink_params_register() (and the inverse functions).  
> > 
> > I have studied the devlink briefly.
> > 
> > However, I find some problems. First, our
> > settings are dependent on the design of
> > both the hardware and firmware. That is,
> > I don't think the others need to do the
> > settings as the same as us. The devlink
> > seems to let everyone could use the same
> > command to do the same setting. However,
> > most of our settings are useless for the
> > other devices.
> > 
> > Second, according to the design of our
> > CMAC, the application has to read and
> > write data with variable length from/to
> > the firmware. Each custom has his own
> > requests. Therefore, our customs would
> > get different firmware with different
> > behavior. Only the application and the
> > firmware know how to communicate with
> > each other. The driver only passes the
> > data between them. Like the Ethernet
> > driver, it doesn't need to know the
> > contend of the packet. I could implement
> > the CMAC through sysfs, but I don't
> > know how to do by devlink.
> > 
> > In brief, CMAC is our major method to
> > configure the firmware and get response
> > from the firmware. Except for certain information,
> > the other settings are not standard and useless
> > for the other vendors.
> > 
> > Is the devlink the only method I could use?
> > Actually, we use IOCTL now. We wish to
> > convert it to sysfs for upstream driver.
> 
> Ah, I've only spotted the enable/disable knob in the patch. 
> If you're exchanging arbitrary binary data with the FW we 
> can't help you. It's not going to fly upstream.

Uhm. I'm not saying sysfs is a proper way to do that, not at all,
buuut...
We have a ton of different subsystems providing a communication
channel between userspace and HW/FW. Chardevices all over the
tree, highly used rpmsg for remoteproc, uio. We have register
dump in Ethtool, as well as get/set for EEPROM, I'd count them
as well.
So it probably isn't a bad idea to provide some standard API for
network drivers to talk to HW/FW from userspace, like get/set or
rx/tx (when having enough caps for sure)? It could be Devlink ops
or Ethtool ops, the latter fits more to me.

Al