netdev - Re: [PATCH net-next-2.6] sfc: Implement ethtool register dump operation

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Message-Id: <1277142725.2100.36.camel@achroite.uk.solarflarecom.com>
Date:	Mon, 21 Jun 2010 18:52:05 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Jeff Garzik <jeff@...zik.org>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-net-drivers@...arflare.com
Subject: Re: [PATCH net-next-2.6] sfc: Implement ethtool register dump
 operation

On Mon, 2010-06-21 at 13:39 -0400, Jeff Garzik wrote:
> On 06/21/2010 09:06 AM, Ben Hutchings wrote:
> > Signed-off-by: Ben Hutchings<bhutchings@...arflare.com>
> > ---
> >   drivers/net/sfc/ethtool.c |   16 +++
> >   drivers/net/sfc/io.h      |    7 +
> >   drivers/net/sfc/nic.c     |  266 +++++++++++++++++++++++++++++++++++++++++++++
> >   drivers/net/sfc/nic.h     |    3 +
> >   4 files changed, 292 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/net/sfc/ethtool.c b/drivers/net/sfc/ethtool.c
> > index 22026bf..81b7f39 100644
> > --- a/drivers/net/sfc/ethtool.c
> > +++ b/drivers/net/sfc/ethtool.c
> > @@ -242,6 +242,20 @@ static void efx_ethtool_get_drvinfo(struct net_device *net_dev,
> >   	strlcpy(info->bus_info, pci_name(efx->pci_dev), sizeof(info->bus_info));
> >   }
> >
> > +static int efx_ethtool_get_regs_len(struct net_device *net_dev)
> > +{
> > +	return efx_nic_get_regs_len(netdev_priv(net_dev));
> > +}
> > +
> > +static void efx_ethtool_get_regs(struct net_device *net_dev,
> > +				 struct ethtool_regs *regs, void *buf)
> > +{
> > +	struct efx_nic *efx = netdev_priv(net_dev);
> > +
> > +	regs->version = efx->type->revision;
> > +	efx_nic_get_regs(efx, buf);
> 
> regs->version is really the version of hardware register dump exported 
> to userspace.  You might want to hardcode this in the driver, to be 
> changed when efx_nic_regs[] array changes, rather than tying 
> regs->version directly to the SFC hardware architecture revision.
>
> However, if that limitation is OK with you, ie. ethtool register dump 
> code will change when h/w arch rev changes, then

This is exactly what we want, as the set of defined registers (and
fields within each register) will change in each architecture revision.
(It may not change in each chip revision, but efx_nic_type::revision is
supposed to reflect the architecture revision.)

Although this code doesn't include an explicit format version, we can
consider the current format to be version 0 and increment it if we ever
want to make changes to the format for existing NIC revisions.

> 	Acked-by: Jeff Garzik <jgarzik@...hat.com>
> 
> This is a ABI-related choice, so it deserves a bit of consideration.

I *think* I know what I'm doing here. :-)

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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