[ 3.5.y.z extended stable ] Patch "staging: comedi: ni_65xx: (bug fix) confine insn_bits to one" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    staging: comedi: ni_65xx: (bug fix) confine insn_bits to one

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From cadbc522e77d5235d07c56d7591845ae41186071 Mon Sep 17 00:00:00 2001
From: Ian Abbott <abbotti at mev.co.uk>
Date: Wed, 2 Oct 2013 14:57:51 +0100
Subject: [PATCH] staging: comedi: ni_65xx: (bug fix) confine insn_bits to one
 subdevice

commit 677a31565692d596ef42ea589b53ba289abf4713 upstream.

The `insn_bits` handler `ni_65xx_dio_insn_bits()` has a `for` loop that
currently writes (optionally) and reads back up to 5 "ports" consisting
of 8 channels each.  It reads up to 32 1-bit channels but can only read
and write a whole port at once - it needs to handle up to 5 ports as the
first channel it reads might not be aligned on a port boundary.  It
breaks out of the loop early if the next port it handles is beyond the
final port on the card.  It also breaks out early on the 5th port in the
loop if the first channel was aligned.  Unfortunately, it doesn't check
that the current port it is dealing with belongs to the comedi subdevice
the `insn_bits` handler is acting on.  That's a bug.

Redo the `for` loop to terminate after the final port belonging to the
subdevice, changing the loop variable in the process to simplify things
a bit.  The `for` loop could now try and handle more than 5 ports if the
subdevice has more than 40 channels, but the test `if (bitshift >= 32)`
ensures it will break out early after 4 or 5 ports (depending on whether
the first channel is aligned on a port boundary).  (`bitshift` will be
between -7 and 7 inclusive on the first iteration, increasing by 8 for
each subsequent operation.)

Signed-off-by: Ian Abbott <abbotti at mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
[ Ian: This patch applies to kernels 2.6.34.y through to 3.5.y inclusive.
  Similar patch already queued for 3.10.y and 3.11.y by Greg-KH.
  I can post similar patches for kernels 3.6.y to 3.9.y on request.
  Similar patch for 2.6.32.y ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/staging/comedi/drivers/ni_65xx.c | 26 +++++++++++---------------
 1 file changed, 11 insertions(+), 15 deletions(-)

diff --git a/drivers/staging/comedi/drivers/ni_65xx.c b/drivers/staging/comedi/drivers/ni_65xx.c
index 0d27a93..c36efe0 100644
--- a/drivers/staging/comedi/drivers/ni_65xx.c
+++ b/drivers/staging/comedi/drivers/ni_65xx.c
@@ -411,29 +411,25 @@ static int ni_65xx_dio_insn_bits(struct comedi_device *dev,
 				 struct comedi_subdevice *s,
 				 struct comedi_insn *insn, unsigned int *data)
 {
-	unsigned base_bitfield_channel;
-	const unsigned max_ports_per_bitfield = 5;
+	int base_bitfield_channel;
 	unsigned read_bits = 0;
-	unsigned j;
+	int last_port_offset = ni_65xx_port_by_channel(s->n_chan - 1);
+	int port_offset;
+
 	if (insn->n != 2)
 		return -EINVAL;
 	base_bitfield_channel = CR_CHAN(insn->chanspec);
-	for (j = 0; j < max_ports_per_bitfield; ++j) {
-		const unsigned port_offset =
-			ni_65xx_port_by_channel(base_bitfield_channel) + j;
-		const unsigned port =
-			sprivate(s)->base_port + port_offset;
-		unsigned base_port_channel;
+	for (port_offset = ni_65xx_port_by_channel(base_bitfield_channel);
+	     port_offset <= last_port_offset; port_offset++) {
+		unsigned port = sprivate(s)->base_port + port_offset;
+		int base_port_channel = port_offset * ni_65xx_channels_per_port;
 		unsigned port_mask, port_data, port_read_bits;
-		int bitshift;
-		if (port >= ni_65xx_total_num_ports(board(dev)))
+		int bitshift = base_port_channel - base_bitfield_channel;
+
+		if (bitshift >= 32)
 			break;
-		base_port_channel = port_offset * ni_65xx_channels_per_port;
 		port_mask = data[0];
 		port_data = data[1];
-		bitshift = base_port_channel - base_bitfield_channel;
-		if (bitshift >= 32 || bitshift <= -32)
-			break;
 		if (bitshift > 0) {
 			port_mask >>= bitshift;
 			port_data >>= bitshift;
--
1.8.3.2