netdev - RE: [PATCH net-next 1/6] ethtool: Extend link modes settings uAPI with lanes

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Message-ID: <DM6PR12MB3865D0B8F8F1BD32532D1DDFD81D0@DM6PR12MB3865.namprd12.prod.outlook.com>
Date:   Thu, 22 Oct 2020 06:15:48 +0000
From:   Danielle Ratson <danieller@...dia.com>
To:     Michal Kubecek <mkubecek@...e.cz>
CC:     Jiri Pirko <jiri@...nulli.us>, Andrew Lunn <andrew@...n.ch>,
        "Jakub Kicinski" <kuba@...nel.org>,
        Ido Schimmel <idosch@...sch.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Jiri Pirko <jiri@...dia.com>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        mlxsw <mlxsw@...dia.com>, Ido Schimmel <idosch@...dia.com>,
        "johannes@...solutions.net" <johannes@...solutions.net>
Subject: RE: [PATCH net-next 1/6] ethtool: Extend link modes settings uAPI
 with lanes



> -----Original Message-----
> From: Michal Kubecek <mkubecek@...e.cz>
> Sent: Wednesday, October 21, 2020 11:48 AM
> To: Danielle Ratson <danieller@...dia.com>
> Cc: Jiri Pirko <jiri@...nulli.us>; Andrew Lunn <andrew@...n.ch>; Jakub
> Kicinski <kuba@...nel.org>; Ido Schimmel <idosch@...sch.org>;
> netdev@...r.kernel.org; davem@...emloft.net; Jiri Pirko
> <jiri@...dia.com>; f.fainelli@...il.com; mlxsw <mlxsw@...dia.com>; Ido
> Schimmel <idosch@...dia.com>; johannes@...solutions.net
> Subject: Re: [PATCH net-next 1/6] ethtool: Extend link modes settings uAPI
> with lanes
> 
> On Wed, Oct 21, 2020 at 07:20:22AM +0000, Danielle Ratson wrote:
> > > -----Original Message-----
> > > From: Michal Kubecek <mkubecek@...e.cz>
> > > Sent: Wednesday, October 21, 2020 10:08 AM
> > >
> > > On Tue, Oct 20, 2020 at 07:39:13AM +0000, Danielle Ratson wrote:
> > > > > -----Original Message-----
> > > > > From: Michal Kubecek <mkubecek@...e.cz>
> > > > > Sent: Monday, October 19, 2020 4:25 PM
> > > > >
> > > > > As I said, I meant the extension suggested in my mail as
> > > > > independent of what this series is about. For lanes count
> > > > > selector, I find proposed
> > > > >
> > > > >   ethtool -s <dev> ... lanes <lanes_num> ...
> > > > >
> > > > > the most natural.
> > > > >
> > > > > From purely syntactic/semantic point of view, there are three
> > > > > types of
> > > > > requests:
> > > > >
> > > > >   (1) enable specific set of modes, disable the rest
> > > > >   (2) enable/disable specific modes, leave the rest as they are
> > > > >   (3) enable modes matching a condition (and disable the rest)
> > > > >
> > > > > What I proposed was to allow the use symbolic names instead of
> > > > > masks (which are getting more and more awful with each new mode)
> > > > > also for (1), like they can already be used for (2).
> > > > >
> > > > > The lanes selector is an extension of (3) which I would prefer
> > > > > not to mix with
> > > > > (1) or (2) within one command line, i.e. either "advertise" or
> > > > > "speed / duplex / lanes".
> > > > >
> > > > > IIUC Jakub's and Andrew's comments were not so much about the
> > > > > syntax and semantic (which is quite clear) but rather about the
> > > > > question if the requests like "advertise exactly the modes with
> > > > > (100Gb/s speed
> > > > > and) two lanes" would really address a real life need and
> > > > > wouldn't be more often used as shortcuts for "advertise
> 100000baseKR2/Full".
> > > > > (On the other hand, I suspect existing speed and duplex
> > > > > selectors are often used the same way.)
> > > > >
> > > > > Michal
> > > >
> > > > So, do you want to change the current approach somehow or we are
> > > > good to go with this one, keeping in mind the future extension you
> > > > have suggested?
> > >
> > > As far as I'm concerned, it makes sense as it is. The only thing I'm
> > > not happy about is ETHTOOL_A_LINKMODES_LANES being a "write only"
> > > attribute (unlike _SPEED and _DUPLEX) but being able to query this
> > > information would require extensive changes far beyond the scope of
> this series.
> >
> > If I understood you correctly, patch #5 does that query, isn't it?
> > "mlxsw: ethtool: Expose the number of lanes in use"
> 
> Ah, right, it does. But as you extend struct ethtool_link_ksettings and drivers
> will need to be updated to provide this information, wouldn't it be more
> useful to let the driver provide link mode in use instead (and derive number
> of lanes from it)?
> 
> Michal

This is the way it is done with the speed parameter, so I have aligned it to it. Why the lanes should be done differently comparing to the speed?