[3.16.y-ckt stable] Patch "staging: comedi: adv_pci1710: fix AI INSN_READ for non-zero channel" 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: adv_pci1710: fix AI INSN_READ for non-zero channel

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt9.

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

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From d1e19c935a9f1e1e9f2dbf13353c6c0832a0d1fa Mon Sep 17 00:00:00 2001
From: Ian Abbott <abbotti at mev.co.uk>
Date: Fri, 27 Feb 2015 16:04:42 +0000
Subject: staging: comedi: adv_pci1710: fix AI INSN_READ for non-zero channel

commit abe46b8932dd9a6dfc3698e3eb121809b7b9ed28 upstream.

Reading of analog input channels by the `INSN_READ` comedi instruction
is broken for all except channel 0.  `pci171x_ai_insn_read()` calls
`pci171x_ai_read_sample()` with the wrong value for the third parameter.
It is supposed to be the current index in a channel list (which is
always of length 1 in this case, so the index should be 0), but instead
it is passing the actual channel number.  `pci171x_ai_read_sample()`
checks the channel number encoded in the raw sample value read from the
hardware matches the channel number stored in the specified index of the
previously set up channel list and returns `-ENODATA` if it doesn't
match.  Since the index should always be 0 in this case, the match will
fail unless the channel number is also 0.  Fix it by passing 0 as the
channel index.

Note that when the bug first appeared, it was `pci171x_ai_dropout()`
that was called with the wrong parameter value.  `pci171x_ai_dropout()`
got replaced with `pci171x_ai_read_sample()` in commit 7fd2dae2500d
("staging: comedi: adv_pci1710: introduce pci171x_ai_read_sample()").

Fixes: 16c7eb6047bb ("staging: comedi: adv_pci1710: always enable PCI171x_PARANOIDCHECK code")
Signed-off-by: Ian Abbott <abbotti at mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
[ luis: backported to 3.16: used Ian's backport ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/staging/comedi/drivers/adv_pci1710.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/staging/comedi/drivers/adv_pci1710.c b/drivers/staging/comedi/drivers/adv_pci1710.c
index 602b7a1e40e6..89de43ffc110 100644
--- a/drivers/staging/comedi/drivers/adv_pci1710.c
+++ b/drivers/staging/comedi/drivers/adv_pci1710.c
@@ -456,7 +456,6 @@ static int pci171x_insn_read_ai(struct comedi_device *dev,
 				struct comedi_insn *insn, unsigned int *data)
 {
 	struct pci1710_private *devpriv = dev->private;
-	unsigned int chan = CR_CHAN(insn->chanspec);
 	int ret = 0;
 	int i;

@@ -478,7 +477,7 @@ static int pci171x_insn_read_ai(struct comedi_device *dev,
 			break;

 		val = inw(dev->iobase + PCI171x_AD_DATA);
-		ret = pci171x_ai_dropout(dev, s, chan, val);
+		ret = pci171x_ai_dropout(dev, s, 0, val);
 		if (ret)
 			break;