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Date: Thu, 30 Oct 2014 15:39:51 -0700 From: Guenter Roeck <linux@...ck-us.net> To: Andrew Lunn <andrew@...n.ch> Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>, Florian Fainelli <f.fainelli@...il.com>, linux-kernel@...r.kernel.org Subject: Re: [PATCH v3 09/15] net: dsa: Add support for switch EEPROM access 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@...665:~# ethtool -e lan4 > Cannot get EEPROM data: Invalid argument > root@...665:~# 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 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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