From: Doug Berger <opendmb@gmail.com>
To: Michal Kubecek <mkubecek@suse.cz>, netdev@vger.kernel.org
Cc: Andrew Lunn <andrew@lunn.ch>,
"David S. Miller" <davem@davemloft.net>,
Florian Fainelli <f.fainelli@gmail.com>,
Heiner Kallweit <hkallweit1@gmail.com>,
Russell King <linux@armlinux.org.uk>,
bcm-kernel-feedback-list@broadcom.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next 1/4] net: ethernet: validate pause autoneg setting
Date: Tue, 12 May 2020 19:37:01 -0700 [thread overview]
Message-ID: <2afd5ca8-c913-6b58-7085-365036098468@gmail.com> (raw)
In-Reply-To: <20200512190855.GB9071@lion.mk-sys.cz>
On 5/12/2020 12:08 PM, Michal Kubecek wrote:
> On Tue, May 12, 2020 at 11:31:39AM -0700, Doug Berger wrote:
>> On 5/11/2020 5:47 PM, Andrew Lunn wrote:
>>> On Mon, May 11, 2020 at 05:24:07PM -0700, Doug Berger wrote:
>>>> A comment in uapi/linux/ethtool.h states "Drivers should reject a
>>>> non-zero setting of @autoneg when autoneogotiation is disabled (or
>>>> not supported) for the link".
>>>>
>>>> That check should be added to phy_validate_pause() to consolidate
>>>> the code where possible.
>>>>
>>>> Fixes: 22b7d29926b5 ("net: ethernet: Add helper to determine if pause configuration is supported")
>>>
>>> Hi Doug
>>>
>>> If this is a real fix, please submit this to net, not net-next.
>>>
>>> Andrew
>>>
>> This was intended as a fix, but I thought it would be better to keep it
>> as part of this set for context and since net-next is currently open.
>>
>> The context is trying to improve the phylib support for offloading
>> ethtool pause configuration and this is something that could be checked
>> in a single location rather than by individual drivers.
>>
>> I included it here to get feedback about its appropriateness as a common
>> behavior. I should have been more explicit about that.
>>
>> Personally, I'm actually not that fond of this change since it can
>> easily be a source of confusion with the ethtool interface because the
>> link autonegotiation and the pause autonegotiation are controlled by
>> different commands.
>>
>> Since the ethtool -A command performs a read/modify/write of pause
>> parameters, you can get strange results like these:
>> # ethtool -s eth0 speed 100 duplex full autoneg off
>> # ethtool -A eth0 tx off
>> Cannot set device pause parameters: Invalid argument
>> #
>> Because, the get read pause autoneg as enabled and only the tx_pause
>> member of the structure was updated.
>
> This would be indeed unfortunate. We could use extack to make the error
> message easier to understand but the real problem IMHO is that
> ethtool_ops::get_pauseparam() returns value which is rejected by
> ethtool_ops::set_pauseparam(). This is something we should avoid.
>
> If we really wanted to reject ethtool_pauseparam::autoneg on when
> general autonegotiation is off, we would have to disable pause
> autonegotiation whenever general autonegotiation is disabled. I don't
> like that idea, however, as that would mean that
>
> ethtool -s dev autoneg off ...
> ethtool -s dev autoneg on ...
>
> would reset the setting of pause autonegotiation.
>
> Therefore I believe the comment should be rather replaced by a warning
> that even if ethtool_pauseparam::autoneg is enabled, pause
> autonegotiation is only active if general autonegotiation is also
> enabled.
>
> Michal
>
Thanks for your reply.
I agree with your concerns and will remove this commit from the set when
I resubmit. I also favor replacing the comment in ethtool.h.
-Doug
next prev parent reply other threads:[~2020-05-13 2:34 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-12 0:24 [PATCH net-next 0/4] Extend phylib implementation of pause support Doug Berger
2020-05-12 0:24 ` [PATCH net-next 1/4] net: ethernet: validate pause autoneg setting Doug Berger
2020-05-12 0:47 ` Andrew Lunn
2020-05-12 18:31 ` Doug Berger
2020-05-12 18:37 ` Andrew Lunn
2020-05-12 18:55 ` Russell King - ARM Linux admin
2020-05-13 3:48 ` Doug Berger
2020-05-13 5:34 ` Russell King - ARM Linux admin
2020-05-13 9:20 ` Russell King - ARM Linux admin
2020-05-13 13:49 ` Andrew Lunn
2020-05-13 14:59 ` Michal Kubecek
2020-05-13 17:14 ` Russell King - ARM Linux admin
2020-05-13 22:09 ` Doug Berger
2020-05-13 21:31 ` Doug Berger
2020-05-13 21:27 ` Doug Berger
2020-05-12 19:08 ` Michal Kubecek
2020-05-13 2:37 ` Doug Berger [this message]
2020-05-12 3:16 ` Florian Fainelli
2020-05-12 0:24 ` [PATCH net-next 2/4] net: add autoneg parameter to linkmode_set_pause Doug Berger
2020-05-12 0:24 ` [PATCH net-next 3/4] net: ethernet: introduce phy_set_pause Doug Berger
2020-05-12 0:51 ` Andrew Lunn
2020-05-12 18:46 ` Doug Berger
2020-05-12 3:22 ` Florian Fainelli
2020-05-13 9:42 ` Russell King - ARM Linux admin
2020-05-13 21:39 ` Doug Berger
2020-05-12 0:24 ` [PATCH net-next 4/4] net: bcmgenet: add support for ethtool flow control Doug Berger
2020-05-12 3:24 ` Florian Fainelli
2020-05-13 9:52 ` Russell King - ARM Linux admin
2020-05-13 22:00 ` Doug Berger
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