staging: comedi: usbdux: bug fix for accessing 'ao_chanlist' in private data
authorH Hartley Sweeten <hsweeten@visionengravers.com>
Fri, 28 Mar 2014 16:20:58 +0000 (09:20 -0700)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 23 Apr 2014 23:20:15 +0000 (16:20 -0700)
commit2704f807f9498054b8153002bafa3e818079e9a5
treea4cca20ab339fcc3832a9c864bf02fd57ae2f2e7
parent8b425aa193439a2b60a988a9230f1de753e36902
staging: comedi: usbdux: bug fix for accessing 'ao_chanlist' in private data

In usbdux_ao_cmd(), the channels for the command are transfered from the
cmd->chanlist and stored in the private data 'ao_chanlist'. The channel
numbers are bit-shifted when stored so that they become the "command"
that is transfered to the device. The channel to command conversion
results in the 'ao_chanlist' having these values for the channels:

  channel 0 -> ao_chanlist = 0x00
  channel 1 -> ao_chanlist = 0x40
  channel 2 -> ao_chanlist = 0x80
  channel 3 -> ao_chanlist = 0xc0

The problem is, the usbduxsub_ao_isoc_irq() function uses the 'chan' value
from 'ao_chanlist' to access the 'ao_readback' array in the private data.
So instead of accessing the array as 0, 1, 2, 3, it accesses it as 0x00,
0x40, 0x80, 0xc0.

Fix this by storing the raw channel number in 'ao_chanlist' and doing the
bit-shift when creating the command.

Fixes: a998a3db530bff80 "staging: comedi: usbdux: cleanup the private data 'outBuffer'"
Cc: stable <stable@vger.kernel.org> # 3.12
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Acked-by: Bernd Porr <mail@berndporr.me.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/staging/comedi/drivers/usbdux.c