linux-kernel - Re: [PATCH net-next] net: mana: Add new device attributes for mana

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Message-ID: <fc345b4d-0747-4ca3-aee0-c53064cc7fe1@lunn.ch>
Date: Fri, 19 Apr 2024 20:51:02 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Shradha Gupta <shradhagupta@...ux.microsoft.com>
Cc: Jason Gunthorpe <jgg@...pe.ca>, Zhu Yanjun <yanjun.zhu@...ux.dev>,
	linux-kernel@...r.kernel.org, linux-hyperv@...r.kernel.org,
	linux-rdma@...r.kernel.org, netdev@...r.kernel.org,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Ajay Sharma <sharmaajay@...rosoft.com>,
	Leon Romanovsky <leon@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
	Long Li <longli@...rosoft.com>,
	Michael Kelley <mikelley@...rosoft.com>,
	Shradha Gupta <shradhagupta@...rosoft.com>,
	Yury Norov <yury.norov@...il.com>,
	Konstantin Taranov <kotaranov@...rosoft.com>,
	Souradeep Chakrabarti <schakrabarti@...ux.microsoft.com>
Subject: Re: [PATCH net-next] net: mana: Add new device attributes for mana

On Fri, Apr 19, 2024 at 09:59:26AM -0700, Shradha Gupta wrote:
> On Thu, Apr 18, 2024 at 08:42:59PM +0200, Andrew Lunn wrote:
> > > >From an RDMA perspective this is all available from other APIs already
> > > at least and I wouldn't want to see new sysfs unless there is a netdev
> > > justification.
> > 
> > It is unlikely there is a netdev justification. Configuration happens
> > via netlink, not sysfs.
> > 
> >     Andrew
> 
> Thanks. Sure, it makes sense to make the generic attribute configurable
> through the netdevice ops or netlink implementation. I will keep that in
> mind while adding the next set of configuration attributes for the driver.
> These attributes(from the patch) however, are hardware specific(that show
> the maximum supported values by the hardware in most cases).

        ndev->max_mtu = gc->adapter_mtu - ETH_HLEN;
        ndev->min_mtu = ETH_MIN_MTU;

This does not appear to be specific to your device. This is very
generic. We already have /sys/class/net/eth42/mtu, why not add
/sys/class/net/eth42/max_mtu and /sys/class/net/eth42/min_mtu for
every driver?

Are these values really hardware specific? Are they really unique to
your hardware? I have to wounder because you clearly did not think
much about MTU, and how it is actually generic...

     Andrew