From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Sowmini Varadhan <sowmini.varadhan@oracle.com>,
linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
benh@kernel.crashing.org, davem@davemloft.net
Subject: Re: [PATCH] iommu-common: Do not use 64 bit constant 0xffffffffffffffffl for computing align_mask
Date: Mon, 20 Jul 2015 19:57:18 +0200 [thread overview]
Message-ID: <87oaj6ogox.fsf@rasmusvillemoes.dk> (raw)
In-Reply-To: <55AC55AD.6070608@roeck-us.net> (Guenter Roeck's message of "Sun, 19 Jul 2015 18:58:05 -0700")
On Mon, Jul 20 2015, Guenter Roeck <linux@roeck-us.net> wrote:
> So either case ~0l appears to be wrong; it should be ~0ul.
Yes, right-shifting -1 of any type is probably always wrong, as it will
always give -1 again. Probably one should add a smatch/sparse warning
for that.
> I don't know if ~0ull makes a difference for some architectures.
I highly doubt it. The result is truncated to unsigned long
anyway. Assuming align_order always has a value between 0 and
BITS_PER_LONG, GENMASK should be exactly what is wanted.
Rasmus
next prev parent reply other threads:[~2015-07-20 17:57 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-19 12:20 Sowmini Varadhan
2015-07-19 15:27 ` Guenter Roeck
2015-07-19 20:25 ` Rasmus Villemoes
2015-07-19 20:41 ` Sowmini Varadhan
2015-07-20 1:58 ` Guenter Roeck
2015-07-20 17:57 ` Rasmus Villemoes [this message]
2015-07-20 19:25 ` Sowmini Varadhan
2015-07-20 23:28 ` Andrew Morton
2015-07-21 0:26 ` Guenter Roeck
2015-07-20 14:44 ` Sowmini Varadhan
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