linux-kernel - Re: [PATCH] iommu-common: Do not use 64 bit constant 0xffffffffffffffffl for computing align

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Date:	Sun, 19 Jul 2015 22:41:42 +0200
From:	Sowmini Varadhan <sowmini.varadhan@...cle.com>
To:	Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:	Guenter Roeck <linux@...ck-us.net>, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, benh@...nel.crashing.org,
	davem@...emloft.net
Subject: Re: [PATCH] iommu-common: Do not use 64 bit  constant
 0xffffffffffffffffl for computing align_mask

On (07/19/15 22:25), Rasmus Villemoes wrote:
> 
> Wouldn't GENMASK(align_order-1, 0) work for all cases (assuming
> align_order has a sane value)?

Devices with limits on DMA masks are uncommon, so I'm personally
not an expert at all the variations in this space, but I was thinking
that this doing 

   align_mask = 0xffffffffffffffffull >> (64 - align_order); 

would be the compact answer for both 32 and 64 bit cases here? 

--Sowmini

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