staging: comedi: pcl818: tidy up pcl818_check()
authorH Hartley Sweeten <hsweeten@visionengravers.com>
Mon, 17 Feb 2014 21:27:57 +0000 (14:27 -0700)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Tue, 18 Feb 2014 19:56:51 +0000 (11:56 -0800)
commit243e7146c8ed16cbda71126168fe73acab7c62d2
tree9ec83183afe570a989bbcb649bdbbbdca9396e8e
parent18c7a6df49d6a1b8d1d59b86bec0ee76e63b44b5
staging: comedi: pcl818: tidy up pcl818_check()

This function probes a number of the boards registers during the
(*attach) to verify that it is actually a PCL-818 compatible board.
For aesthetics, move the function closer to the (*attach).

Refactor the function to return an errno if fails. Change the errno
from -EIO to -ENODEV and remove the unnecessary comedi_error() noise.

Make sure the CONTROL register is reset to a known state after the
check. The 0x18 value actually defines an invalid interrupt selection
and sets an undefined bit.

Add a couple comments to clarify the magic values.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/staging/comedi/drivers/pcl818.c