netdev - Re: [PATCH net-next v6 1/7] net: ethtool: pass ethtool_rxfh to get/set

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Message-ID: <20231121152906.2dd5f487@kernel.org>
Date: Tue, 21 Nov 2023 15:29:06 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Ahmed Zaki <ahmed.zaki@...el.com>
Cc: netdev@...r.kernel.org, intel-wired-lan@...ts.osuosl.org,
 corbet@....net, jesse.brandeburg@...el.com, anthony.l.nguyen@...el.com,
 davem@...emloft.net, edumazet@...gle.com, pabeni@...hat.com,
 vladimir.oltean@....com, andrew@...n.ch, horms@...nel.org,
 mkubecek@...e.cz, willemdebruijn.kernel@...il.com, gal@...dia.com,
 alexander.duyck@...il.com, linux-doc@...r.kernel.org, Igor Bagnucki
 <igor.bagnucki@...el.com>, Jacob Keller <jacob.e.keller@...el.com>
Subject: Re: [PATCH net-next v6 1/7] net: ethtool: pass ethtool_rxfh to
 get/set_rxfh ethtool ops

On Mon, 20 Nov 2023 13:56:08 -0700 Ahmed Zaki wrote:
>  	u32	(*get_rxfh_key_size)(struct net_device *);
>  	u32	(*get_rxfh_indir_size)(struct net_device *);
> -	int	(*get_rxfh)(struct net_device *, u32 *indir, u8 *key,
> -			    u8 *hfunc);
> -	int	(*set_rxfh)(struct net_device *, const u32 *indir,
> -			    const u8 *key, const u8 hfunc);
> +	int	(*get_rxfh)(struct net_device *, struct ethtool_rxfh *,
> +			    u32 *indir, u8 *key);
> +	int	(*set_rxfh)(struct net_device *, struct ethtool_rxfh *,
> +			    const u32 *indir, const u8 *key);
>  	int	(*get_rxfh_context)(struct net_device *, u32 *indir, u8 *key,
>  				    u8 *hfunc, u32 rss_context);
>  	int	(*set_rxfh_context)(struct net_device *, const u32 *indir,

This conversion looks 1/4th done. You should do the following:

 - First simplify the code by always providing a pointer to all params
   (indir, key and func); the fact that some of them may be NULL seems
   like a weird historic thing or a premature optimization.
   It will simplify the drivers if all pointers are always present.
   You don't have to remove the if () checks in the existing drivers.

 - Then make the functions take a dev pointer, and a pointer to a
   single struct wrapping all arguments. The set_* should also take
   an extack.

 - Add a rss_context member to the argument struct and a capability
   like cap_link_lanes_supported to indicate whether driver supports
   rss contexts, then you can remove *et_rxfh_context functions,
   and instead call *et_rxfh() with a non-zero rss_context.

 - Add your new member to the struct wrapping all params.

If you just expose struct ethtool_rxfh to the drivers (a) there are
fields in there drivers shouldn't touch, and (b) that struct is uAPI
so we can't add netlink-only fields easily.