linux-kernel - [PATCH 7/8] firewire: ohci: fix IR/IT context mask mixup

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Date:	Sun, 21 Feb 2010 17:58:52 +0100 (CET)
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	linux1394-devel@...ts.sourceforge.net
cc:	linux-kernel@...r.kernel.org
Subject: [PATCH 7/8] firewire: ohci: fix IR/IT context mask mixup

This bug was present in firewire-ohci since day one:  The number of
available isochronous receive DMA contexts was mixed up with that of
available isochronous transmit DMA contexts.

This is harmless on a few chips which offer the same number of contexts
in both directions, but most chips nowadays implement only the standard
minimum of 4 IR contexts, but 8 IT contexts.  If a user attempted to run
a lot of IR contexts at once, results with more than four were therefore
unpredictable.  I suppose the controller would simply refuse to start
DMA of any unimplemented context.

Signed-off-by: Stefan Richter <stefanr@...6.in-berlin.de>
---
 drivers/firewire/ohci.c |   14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

Index: b/drivers/firewire/ohci.c
===================================================================
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -2395,17 +2395,17 @@ static int __devinit pci_probe(struct pc
 		     OHCI1394_AsRspTrContextControlSet, handle_at_packet);
 
 	reg_write(ohci, OHCI1394_IsoRecvIntMaskSet, ~0);
-	ohci->it_context_mask = reg_read(ohci, OHCI1394_IsoRecvIntMaskSet);
+	ohci->ir_context_channels = ~0ULL;
+	ohci->ir_context_mask = reg_read(ohci, OHCI1394_IsoRecvIntMaskSet);
 	reg_write(ohci, OHCI1394_IsoRecvIntMaskClear, ~0);
-	size = sizeof(struct iso_context) * hweight32(ohci->it_context_mask);
-	ohci->it_context_list = kzalloc(size, GFP_KERNEL);
+	size = sizeof(struct iso_context) * hweight32(ohci->ir_context_mask);
+	ohci->ir_context_list = kzalloc(size, GFP_KERNEL);
 
 	reg_write(ohci, OHCI1394_IsoXmitIntMaskSet, ~0);
-	ohci->ir_context_channels = ~0ULL;
-	ohci->ir_context_mask = reg_read(ohci, OHCI1394_IsoXmitIntMaskSet);
+	ohci->it_context_mask = reg_read(ohci, OHCI1394_IsoXmitIntMaskSet);
 	reg_write(ohci, OHCI1394_IsoXmitIntMaskClear, ~0);
-	size = sizeof(struct iso_context) * hweight32(ohci->ir_context_mask);
-	ohci->ir_context_list = kzalloc(size, GFP_KERNEL);
+	size = sizeof(struct iso_context) * hweight32(ohci->it_context_mask);
+	ohci->it_context_list = kzalloc(size, GFP_KERNEL);
 
 	if (ohci->it_context_list == NULL || ohci->ir_context_list == NULL) {
 		err = -ENOMEM;

-- 
Stefan Richter
-=====-==-=- --=- =-=-=
http://arcgraph.de/sr/

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