netdev - RE: [PATCH net] mlx4_en: set number of rx rings used by RSS using ethtool

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Date:	Tue, 17 Jan 2012 17:22:18 -0000
From:	"David Laight" <David.Laight@...LAB.COM>
To:	"David Miller" <davem@...emloft.net>, <yevgenyp@...lanox.co.il>
Cc:	<netdev@...r.kernel.org>, <amirv@...lanox.co.il>
Subject: RE: [PATCH net] mlx4_en: set number of rx rings used by RSS using ethtool

 
> > +	/* RSS table size must be an order of 2 */
> > +	if (rss_rings != (1 << order_base_2(rss_rings)))
> > +		return -EINVAL;
> 
> This is an obscure way to make this kind of test.
> 
> The canonical way is:
> 
> 	if (is_power_of_2(rss_rings))

Which is probably (x & {x-1)) == 0

	David


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