netdev - Re: [PATCH net-next 3/4] ethtool: Support for configurable RSS hash key.

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Message-ID: <1390156048.16433.114.camel@deadeye.wl.decadent.org.uk>
Date:	Sun, 19 Jan 2014 18:27:28 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Venkata Duvvuru <VenkatKumar.Duvvuru@...lex.Com>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 3/4] ethtool: Support for configurable RSS hash
 key.

On Fri, 2014-01-17 at 13:02 +0000, Venkata Duvvuru wrote:
> This ethtool patch primarily copies the ioctl command data structures from/to the User space and invokes the driver hook.
[...]
> --- a/include/uapi/linux/ethtool.h
> +++ b/include/uapi/linux/ethtool.h
> @@ -678,6 +678,22 @@ struct ethtool_rx_ntuple {
>  	struct ethtool_rx_ntuple_flow_spec	fs;
>  };
>  
> +
> +/**
> + * struct ethtool_rss_hkey - command to set/get RSS hash key of the device.
> + * @cmd: Command number - %ETHTOOL_SET_RSS_HKEY/ETHTOOL_GET_RSS_HKEY
> + * @data: 40 or 16 byte rss hash key
> + * @data_len: rss hash key length
> + */
> +
> +#define RSS_HASH_KEY_LEN	40

This should have an 'ETHTOOL_' or 'ETH_' prefix.  But I wonder whether
there should actually be a static maximum length.

> +/* RSS Hash key */
> +struct ethtool_rss_hkey {
> +	__u32   cmd;            /* ETHTOOL_SET/GET_RSS_HKEY */
> +	__u8    data[RSS_HASH_KEY_LEN];
> +	__u32	data_len;
> +};
[...]

How about putting data after the data_len and giving it a length of 0,
so this is extensible to an arbitrary length key?

If we're extending the RSS configuration interface, there are a few
other things that might be worth doing at the same time:

- Single commands to get/set both the key and the indirection table at
the same time
- Add a field to distinguish multiple RSS contexts (some hardware can
use RSS contexts together with filters, though RX NFC does not support
that yet)

Ben.

-- 
Ben Hutchings
friends: People who know you well, but like you anyway.

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