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staging: comedi: pcl818: tidy up pcl818_check()

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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>
This commit is contained in:
H Hartley Sweeten 2014-02-17 14:27:57 -07:00 committed by Greg Kroah-Hartman
parent 18c7a6df49
commit 243e7146c8
1 changed files with 27 additions and 23 deletions
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50
drivers/staging/comedi/drivers/pcl818.c
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@ -1082,25 +1082,6 @@ end:
return 0;
}
static int pcl818_check(unsigned long iobase)
{
outb(0x00, iobase + PCL818_MUX);
udelay(1);
if (inb(iobase + PCL818_MUX) != 0x00)
return 1; /* there isn't card */
outb(0x55, iobase + PCL818_MUX);
udelay(1);
if (inb(iobase + PCL818_MUX) != 0x55)
return 1; /* there isn't card */
outb(0x00, iobase + PCL818_MUX);
udelay(1);
outb(0x18, iobase + PCL818_CONTROL);
udelay(1);
if (inb(iobase + PCL818_CONTROL) != 0x18)
return 1; /* there isn't card */
return 0; /* ok, card exist */
}
static void pcl818_reset(struct comedi_device *dev)
{
const struct pcl818_board *board = comedi_board(dev);
@ -1187,6 +1168,30 @@ static void pcl818_set_ai_range_table(struct comedi_device *dev,
}
}
static int pcl818_check(struct comedi_device *dev)
{
/* the MUX register should return the same value written */
outb(0x00, dev->iobase + PCL818_MUX);
if (inb(dev->iobase + PCL818_MUX) != 0x00)
return -ENODEV;
outb(0x55, dev->iobase + PCL818_MUX);
if (inb(dev->iobase + PCL818_MUX) != 0x55)
return -ENODEV;
/* reset the MUX register to a known state */
outb(0x00, dev->iobase + PCL818_MUX);
/* the CONTROL register should return the same value written */
outb(0x18, dev->iobase + PCL818_CONTROL);
if (inb(dev->iobase + PCL818_CONTROL) != 0x18)
return -ENODEV;
/* reset the CONTROL register to a known state */
outb(0x00, dev->iobase + PCL818_CONTROL);
return 0;
}
static int pcl818_attach(struct comedi_device *dev, struct comedi_devconfig *it)
{
const struct pcl818_board *board = comedi_board(dev);
@ -1208,10 +1213,9 @@ static int pcl818_attach(struct comedi_device *dev, struct comedi_devconfig *it)
if (ret)
return ret;
if (pcl818_check(dev->iobase)) {
comedi_error(dev, "I can't detect board. FAIL!\n");
return -EIO;
}
ret = pcl818_check(dev);
if (ret)
return ret;
/* we can use IRQ 2-7 for async command support */
if (it->options[1] >= 2 && it->options[1] <= 7) {