netdev - Re: [RFC net-next 1/1] ethtool: Add support for set eeprom metadata.

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Message-ID: <1465130957.2847.195.camel@decadent.org.uk>
Date:	Sun, 05 Jun 2016 13:49:17 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Yuval Mintz <Yuval.Mintz@...gic.com>,
	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>,
	Sudarsana Kalluru <Sudarsana.Kalluru@...gic.com>
Subject: Re: [RFC net-next 1/1] ethtool: Add support for set eeprom metadata.

On Sun, 2016-06-05 at 10:16 +0000, Yuval Mintz wrote:
> > 
> > Currently ethtool implementation does not have a way to pass the metadata for
> > eeprom related operations. Some adapters have a complicated non-volatile
> > memory implementation that requires additional information – there are drivers
> > [bnx2x and bnxt] that use the ‘magic’ field in the {G,S}EEPROM  for that purpose,
> > although that’s not its intended usage.
> > 
> > This patch adds a provision to pass the eeprom metadata for
> > %ETHTOOL_SEEPROM/%ETHTOOL_GEEPROM implementations. User provided
> > metadata will be cached by the driver and assigns a magic value which the
> > application need to use for the subsequent {G,S}EEPROM command.
> 
> Hi Dave,
> 
> This got no comments at all.
> What do you want us to with it next? Should we re-send it as a patch?

Here's a comment: I really dislike this.

- It doesn't specify any semantics for the 'metadata'.  The comment
hints that they are driver-specific identifiers for different NVRAM
partitions.

- It doesn't provide a way for userland to enumerate the valid metadata
values.

- It's not clear whether the driver is supposed to maintain just one
metadata:magic mapping, or more than that.

Is the ethtool API really the right interface for access to flash?  The
sfc driver exposes a large number of flash partitions using MTD
instead.  These can be enumerated (through /proc/mtd or sysfs) and they
can be read and written through block devices.

Ben.

-- 
Ben Hutchings
Everything should be made as simple as possible, but not simpler.
                                                           - Albert
Einstein

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