linux-kernel - [PATCH 1/2] xhci: Use ilog2() rather than __ffs() for calculating SEGMENT

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Message-ID: <20130328184827.29679.62426.stgit@warthog.procyon.org.uk>
Date:	Thu, 28 Mar 2013 18:48:28 +0000
From:	David Howells <dhowells@...hat.com>
To:	sarah.a.sharp@...ux.intel.com
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] xhci: Use ilog2() rather than __ffs() for calculating
 SEGMENT_SHIFT

Use ilog2() rather than __ffs() for calculating SEGMENT_SHIFT as ilog2() can
be worked out at compile time, whereas __ffs() must be calculated at runtime.

Signed-off-by: David Howells <dhowells@...hat.com>
cc: Sarah Sharp <sarah.a.sharp@...ux.intel.com>
cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
cc: linux-usb@...r.kernel.org
---

 drivers/usb/host/xhci.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index 2c510e4..558ba50 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1235,7 +1235,7 @@ union xhci_trb {
 /* Allow two commands + a link TRB, along with any reserved command TRBs */
 #define MAX_RSVD_CMD_TRBS	(TRBS_PER_SEGMENT - 3)
 #define SEGMENT_SIZE		(TRBS_PER_SEGMENT*16)
-#define SEGMENT_SHIFT		(__ffs(SEGMENT_SIZE))
+#define SEGMENT_SHIFT		(ilog2(SEGMENT_SIZE))
 /* TRB buffer pointers can't cross 64KB boundaries */
 #define TRB_MAX_BUFF_SHIFT		16
 #define TRB_MAX_BUFF_SIZE	(1 << TRB_MAX_BUFF_SHIFT)

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