From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161490AbaJ3WkO (ORCPT ); Thu, 30 Oct 2014 18:40:14 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:38886 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161474AbaJ3WkJ (ORCPT ); Thu, 30 Oct 2014 18:40:09 -0400 Date: Thu, 30 Oct 2014 15:39:51 -0700 From: Guenter Roeck To: Andrew Lunn Cc: netdev@vger.kernel.org, "David S. Miller" , Florian Fainelli , linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 09/15] net: dsa: Add support for switch EEPROM access Message-ID: <20141030223951.GA19489@roeck-us.net> References: <1414604707-22407-1-git-send-email-linux@roeck-us.net> <1414604707-22407-10-git-send-email-linux@roeck-us.net> <20141030211131.GB32139@lunn.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141030211131.GB32139@lunn.ch> User-Agent: Mutt/1.5.21 (2010-09-15) X-Authenticated_sender: guenter@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-CTCH-PVer: 0000001 X-CTCH-Spam: Unknown X-CTCH-VOD: Unknown X-CTCH-Flags: 0 X-CTCH-RefID: str=0001.0A020209.5452BE48.02A1,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0 X-CTCH-Score: 0.000 X-CTCH-ScoreCust: 0.000 X-CTCH-Rules: C_4847, X-CTCH-SenderID: linux@roeck-us.net X-CTCH-SenderID-Flags: 0 X-CTCH-SenderID-TotalMessages: 5 X-CTCH-SenderID-TotalSpam: 0 X-CTCH-SenderID-TotalSuspected: 0 X-CTCH-SenderID-TotalConfirmed: 0 X-CTCH-SenderID-TotalBulk: 0 X-CTCH-SenderID-TotalVirus: 0 X-CTCH-SenderID-TotalRecipients: 0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: mailgid no entry from get_relayhosts_entry X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 30, 2014 at 10:11:31PM +0100, Andrew Lunn wrote: > > +static int dsa_slave_get_eeprom_len(struct net_device *dev) > > +{ > > + struct dsa_slave_priv *p = netdev_priv(dev); > > + struct dsa_switch *ds = p->parent; > > + > > + if (ds->pd->eeprom_len) > > + return ds->pd->eeprom_len; > > + > > + if (ds->drv->get_eeprom_len) > > + return ds->drv->get_eeprom_len(ds); > > + > > + return 0; > > +} > > + > > Hi Guenter > > I just started doing some testing with this patchset. A bit late since > David just accepted it, but... > > root@dir665:~# ethtool -e lan4 > Cannot get EEPROM data: Invalid argument > root@dir665:~# ethtool -e eth0 > Cannot get EEPROM data: Operation not supported > > There is no eeprom for the hardware i'm testing. Operation not > supported seems like a better error code and Invalid argument, and is > what other network drivers i tried returned. > Hi Andrew, I think the problem is that the infrastructure code (net/core/ethtool.c) does not accept an error from the get_eeprom_len function, but instead assumes that reporting eeprom data is supported if a driver provides the access functions. The get_eeprom_len function returns 0 in your case, which in ethtool_get_any_eeprom() translates to -EINVAL because user space either requests no data or more data than available. I wonder why user space requests anything in the first place; I would have assumed that it reads the driver information first and is told that the eeprom length is 0, but I guess that is a different question. I quickly browsed through a couple of other drivers supporting get_eprom_len, and they all return 0 if there is no eeprom. Doesn't that mean that they all end up reporting -EINVAL if an attempt is made to read the eeprom ? The only solution that comes to my mind would be to have the infrastructure code check the return value from get_eeprom_len and return -EOPNOTSUPP if the reported eeprom length is 0. That would be an infrastructure change, though. Does that sound reasonable, or do you have a better idea ? In parallel, I'll have a look into the ethtool command to see why it requests eeprom data even though the reported eeprom length is 0. Thanks, Guenter