[patch 39/46] USB: EHCI: fix divide-by-zero bug

[Greg KH <gregkh@suse.de>]

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2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Alan Stern <stern@rowland.harvard.edu>

commit 372dd6e8ed924e876f3beb598721e813ad7fa323 upstream.

This patch (as1164) fixes a bug in the EHCI scheduler.  The interval
value it uses is already in linear format, not logarithmically coded.
The existing code can sometimes crash the system by trying to divide
by zero.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 drivers/usb/host/ehci-sched.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -918,7 +918,7 @@ iso_stream_init (
 		 */
 		stream->usecs = HS_USECS_ISO (maxp);
 		bandwidth = stream->usecs * 8;
-		bandwidth /= 1 << (interval - 1);
+		bandwidth /= interval;
 
 	} else {
 		u32		addr;
@@ -951,7 +951,7 @@ iso_stream_init (
 		} else
 			stream->raw_mask = smask_out [hs_transfers - 1];
 		bandwidth = stream->usecs + stream->c_usecs;
-		bandwidth /= 1 << (interval + 2);
+		bandwidth /= interval << 3;
 
 		/* stream->splits gets created from raw_mask later */
 		stream->address = cpu_to_hc32(ehci, addr);

--